diff --git a/interface/src/i18n/de/index.ts b/interface/src/i18n/de/index.ts
index 9627a017d..fe9a40b67 100644
--- a/interface/src/i18n/de/index.ts
+++ b/interface/src/i18n/de/index.ts
@@ -332,7 +332,8 @@ const de: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate
+  RENAME: 'Rename', // TODO translate
+  ENABLE_MODBUS: 'Modbus aktivieren'
 };
 
 export default de;
diff --git a/interface/src/i18n/en/index.ts b/interface/src/i18n/en/index.ts
index 3846441bf..ce1762eda 100644
--- a/interface/src/i18n/en/index.ts
+++ b/interface/src/i18n/en/index.ts
@@ -332,7 +332,8 @@ const en: Translation = {
   MODULES_UPDATED: 'Modules updated',
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules',
   MODULES_NONE: 'No external modules detected',
-  RENAME: 'Rename'
+  RENAME: 'Rename',
+  ENABLE_MODBUS: 'Enable Modbus'
 };
 
 export default en;
diff --git a/interface/src/i18n/fr/index.ts b/interface/src/i18n/fr/index.ts
index fb4e0de39..3354f122f 100644
--- a/interface/src/i18n/fr/index.ts
+++ b/interface/src/i18n/fr/index.ts
@@ -332,7 +332,8 @@ const fr: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate
+  RENAME: 'Rename', // TODO translate
+  ENABLE_MODBUS: 'Activer Modbus'
 };
 
 export default fr;
diff --git a/interface/src/i18n/it/index.ts b/interface/src/i18n/it/index.ts
index 124e76a04..c7daac020 100644
--- a/interface/src/i18n/it/index.ts
+++ b/interface/src/i18n/it/index.ts
@@ -332,7 +332,8 @@ const it: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate  
+  RENAME: 'Rename', // TODO translate  
+  ENABLE_MODBUS: 'Abilita Modbus'
 };
 
 export default it;
diff --git a/interface/src/i18n/nl/index.ts b/interface/src/i18n/nl/index.ts
index 02d2e5ea5..c643913ac 100644
--- a/interface/src/i18n/nl/index.ts
+++ b/interface/src/i18n/nl/index.ts
@@ -332,7 +332,8 @@ const nl: Translation = {
   MODULES_UPDATED: 'Modules geüpdatet', 
   MODULES_DESCRIPTION: 'Klik op de module om EMS-ESP library modules te activeren of te deactiveren',
   MODULES_NONE: 'Geen externe modules gedetecteerd',
-  RENAME: 'Hernoemen'
+  RENAME: 'Hernoemen',
+  ENABLE_MODBUS: 'Activeer Modbus'
 };
 
 export default nl;
diff --git a/interface/src/i18n/no/index.ts b/interface/src/i18n/no/index.ts
index 2d053ebe7..7d961a727 100644
--- a/interface/src/i18n/no/index.ts
+++ b/interface/src/i18n/no/index.ts
@@ -332,7 +332,8 @@ const no: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate 
+  RENAME: 'Rename', // TODO translate 
+  ENABLE_MODBUS: 'Aktiver Modbus'
 };
 
 export default no;
diff --git a/interface/src/i18n/pl/index.ts b/interface/src/i18n/pl/index.ts
index b367ebce9..ee4df7ba1 100644
--- a/interface/src/i18n/pl/index.ts
+++ b/interface/src/i18n/pl/index.ts
@@ -332,7 +332,8 @@ const pl: BaseTranslation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate 
+  RENAME: 'Rename', // TODO translate 
+  ENABLE_MODBUS: 'Aktywuj Modbus'
 };
 
 export default pl;
diff --git a/interface/src/i18n/sk/index.ts b/interface/src/i18n/sk/index.ts
index cd83f5893..0b75b8b6d 100644
--- a/interface/src/i18n/sk/index.ts
+++ b/interface/src/i18n/sk/index.ts
@@ -332,6 +332,8 @@ const sk: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate 
+  RENAME: 'Rename', // TODO translate 
+  ENABLE_MODBUS: 'Povoliť Modbus'
 };
+
 export default sk;
diff --git a/interface/src/i18n/sv/index.ts b/interface/src/i18n/sv/index.ts
index 6977ee6c7..22fb3ed59 100644
--- a/interface/src/i18n/sv/index.ts
+++ b/interface/src/i18n/sv/index.ts
@@ -332,7 +332,8 @@ const sv: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate 
+  RENAME: 'Rename', // TODO translate
+  ENABLE_MODBUS: 'Aktivera Modbus'
 };
 
 export default sv;
diff --git a/interface/src/i18n/tr/index.ts b/interface/src/i18n/tr/index.ts
index 9b95cf8d8..95ab995c1 100644
--- a/interface/src/i18n/tr/index.ts
+++ b/interface/src/i18n/tr/index.ts
@@ -332,7 +332,8 @@ const tr: Translation = {
   MODULES_UPDATED: 'Modules updated', // TODO translate
   MODULES_DESCRIPTION: 'Click on the Module to activate or de-activate EMS-ESP library modules', // TODO translate
   MODULES_NONE: 'No external modules detected', // TODO translate
-  RENAME: 'Rename' // TODO translate 
+  RENAME: 'Rename', // TODO translate 
+  ENABLE_MODBUS: 'Enable Modbus' // TODO translate
 };
 
 export default tr;
diff --git a/interface/src/project/ApplicationSettings.tsx b/interface/src/project/ApplicationSettings.tsx
index 7b20ba357..069863994 100644
--- a/interface/src/project/ApplicationSettings.tsx
+++ b/interface/src/project/ApplicationSettings.tsx
@@ -826,6 +826,75 @@ const ApplicationSettings: FC = () => {
             </Grid>
           </Grid>
         )}
+        <Typography sx={{ pt: 2 }} variant="h6" color="primary">
+          Modbus
+        </Typography>
+        <BlockFormControlLabel
+          control={
+            <Checkbox
+              checked={data.modbus_enabled}
+              onChange={updateFormValue}
+              name="modbus_enabled"
+              disabled={saving}
+            />
+          }
+          label={LL.ENABLE_MODBUS()}
+        />
+        {data.modbus_enabled && (
+          <Grid
+            container
+            spacing={1}
+            direction="row"
+            justifyContent="flex-start"
+            alignItems="flex-start"
+          >
+            <Grid item xs={12} sm={6}>
+              <ValidatedTextField
+                fieldErrors={fieldErrors}
+                name="modbus_max_clients"
+                label={LL.AP_MAX_CLIENTS()}
+                fullWidth
+                variant="outlined"
+                value={numberValue(data.modbus_max_clients)}
+                type="number"
+                onChange={updateFormValue}
+                margin="normal"
+                disabled={saving}
+              />
+            </Grid>
+            <Grid item xs={12} sm={6}>
+              <ValidatedTextField
+                fieldErrors={fieldErrors}
+                name="modbus_port"
+                label="Port"
+                fullWidth
+                variant="outlined"
+                value={numberValue(data.modbus_port)}
+                type="number"
+                onChange={updateFormValue}
+                margin="normal"
+                disabled={saving}
+              />
+            </Grid>
+            <Grid item xs={12} sm={6}>
+              <ValidatedTextField
+                fieldErrors={fieldErrors}
+                name="modbus_timeout"
+                label="Timeout"
+                InputProps={{
+                  endAdornment: <InputAdornment position="end">ms</InputAdornment>
+                }}
+                fullWidth
+                variant="outlined"
+                value={numberValue(data.modbus_timeout)}
+                type="number"
+                onChange={updateFormValue}
+                margin="normal"
+                disabled={saving}
+              />
+            </Grid>
+          </Grid>
+        )}
         {restartNeeded && (
           <MessageBox my={2} level="warning" message={LL.RESTART_TEXT(0)}>
             <Button
diff --git a/interface/src/project/types.ts b/interface/src/project/types.ts
index 82e5f55e8..05907fcfb 100644
--- a/interface/src/project/types.ts
+++ b/interface/src/project/types.ts
@@ -38,6 +38,10 @@ export interface Settings {
   eth_phy_addr: number;
   eth_clock_mode: number;
   platform: string;
+  modbus_enabled: boolean;
+  modbus_port: number;
+  modbus_max_clients: number;
+  modbus_timeout: number;
 }
 
 export enum busConnectionStatus {
diff --git a/lib/eModbus/README.md b/lib/eModbus/README.md
new file mode 100644
index 000000000..cbda1fccf
--- /dev/null
+++ b/lib/eModbus/README.md
@@ -0,0 +1,26 @@
+
+<img src=https://github.com/eModbus/eModbus/blob/master/eModbusLogo.png width="33%" alt="eModbus">
+
+**Read the docs at http://emodbus.github.io!**
+
+![eModbus](https://github.com/eModbus/eModbus/workflows/Building/badge.svg)
+
+This is a library to provide Modbus client (formerly known as master), server (formerly slave) and bridge/gateway functionalities for Modbus RTU, ASCII and TCP protocols.
+
+For Modbus protocol specifications, please refer to the [Modbus.org site](https://www.modbus.org/specs.php)!
+
+Modbus communication is done in separate tasks, so Modbus requests and responses are non-blocking. Callbacks are provided to prepare or receive the responses asynchronously.
+
+Key features:
+- for use in the Arduino framework
+- designed for ESP32, various interfaces supported; async versions run also on ESP8266
+- non blocking / asynchronous API
+- server, client and bridge modes
+- TCP (Ethernet, WiFi and Async), ASCII and RTU interfaces
+- all common and user-defined Modbus standard function codes 
+
+This has been developed by enthusiasts. While we do our utmost best to make robust software, do not expect any bullet-proof, industry deployable, guaranteed software. [**See the license**](https://github.com/eModbus/eModbus/blob/master/license.md) to learn about liabilities etc.
+
+We do welcome any ideas, suggestions, bug reports or questions. Please use the "[Issues](https://github.com/eModbus/eModbus/issues)" tab to report bugs and request new features and visit the "[Discussions](https://github.com/eModbus/eModbus/discussions)" tab for all else.
+
+Have fun!
diff --git a/lib/eModbus/keywords.txt b/lib/eModbus/keywords.txt
new file mode 100644
index 000000000..fbbc9db52
--- /dev/null
+++ b/lib/eModbus/keywords.txt
@@ -0,0 +1,257 @@
+#######################################
+# Syntax Coloring Map For the current project.
+# This file was generated by doxygen2keywords.xsl.
+#######################################
+
+#######################################
+# Classes and structs (KEYWORD1)
+#######################################
+
+ModbusServerTCP::ClientData	KEYWORD1
+CoilData	KEYWORD1
+Modbus::FCT	KEYWORD1
+ModbusBridge	KEYWORD1
+ModbusClient	KEYWORD1
+ModbusClientTCP	KEYWORD1
+ModbusClientRTU	KEYWORD1
+ModbusClientTCPasync	KEYWORD1
+ModbusError	KEYWORD1
+ModbusMessage	KEYWORD1
+ModbusServer	KEYWORD1
+ModbusServerTCP	KEYWORD1
+ModbusServerRTU	KEYWORD1
+ModbusServerTCPasync	KEYWORD1
+RTUutils	KEYWORD1
+
+#######################################
+# Methods (KEYWORD2)
+#######################################
+
+ClientData	KEYWORD2
+~ClientData	KEYWORD2
+CoilData	KEYWORD2
+~CoilData	KEYWORD2
+coils	KEYWORD2
+coilsSetON	KEYWORD2
+coilsSetOFF	KEYWORD2
+FCT	KEYWORD2
+getType	KEYWORD2
+redefineType	KEYWORD2
+ModbusBridge	KEYWORD2
+attachServer	KEYWORD2
+addFunctionCode	KEYWORD2
+denyFunctionCode	KEYWORD2
+bridgeWorker	KEYWORD2
+bridgeDenyWorker	KEYWORD2
+onDataHandler	KEYWORD2
+onErrorHandler	KEYWORD2
+onResponseHandler	KEYWORD2
+getMessageCount	KEYWORD2
+getErrorCount	KEYWORD2
+resetCounts	KEYWORD2
+addRequest	KEYWORD2
+syncRequest	KEYWORD2
+buildErrorMsg	KEYWORD2
+addRequest	KEYWORD2
+ModbusClient	KEYWORD2
+waitSync	KEYWORD2
+ModbusClientTCPasync	KEYWORD2
+setTimeout	KEYWORD2
+setIdleTimeout	KEYWORD2
+setMaxInflightRequests	KEYWORD2
+addToQueue	KEYWORD2
+ModbusError	KEYWORD2
+getText	KEYWORD2
+ModbusMessage	KEYWORD2
+data	KEYWORD2
+size	KEYWORD2
+push_back	KEYWORD2
+clear	KEYWORD2
+resize	KEYWORD2
+begin	KEYWORD2
+end	KEYWORD2
+append	KEYWORD2
+getServerID	KEYWORD2
+getFunctionCode	KEYWORD2
+getError	KEYWORD2
+setFunctionCode	KEYWORD2
+add	KEYWORD2
+get	KEYWORD2
+setMessage	KEYWORD2
+setError	KEYWORD2
+determineFloatOrder	KEYWORD2
+determineDoubleOrder	KEYWORD2
+swapFloat	KEYWORD2
+swapDouble	KEYWORD2
+getOne	KEYWORD2
+registerWorker	KEYWORD2
+getWorker	KEYWORD2
+unregisterWorker	KEYWORD2
+isServerFor	KEYWORD2
+getMessageCount	KEYWORD2
+getErrorCount	KEYWORD2
+resetCounts	KEYWORD2
+localRequest	KEYWORD2
+listServer	KEYWORD2
+ModbusServer	KEYWORD2
+ModbusServerTCP	KEYWORD2
+activeClients	KEYWORD2
+start	KEYWORD2
+stop	KEYWORD2
+clientAvailable	KEYWORD2
+ModbusServerTCPasync	KEYWORD2
+isRunning	KEYWORD2
+calcCRC	KEYWORD2
+validCRC	KEYWORD2
+addCRC	KEYWORD2
+calculateInterval	KEYWORD2
+prepareHardwareSerial	KEYWORD2
+RTUutils	KEYWORD2
+ServerData	KEYWORD2
+NIL_RESPONSE	KEYWORD2
+ECHO_RESPONSE	KEYWORD2
+
+#######################################
+# Constants (LITERAL1)
+#######################################
+
+DISCONNECTED	LITERAL1
+CONNECTING	LITERAL1
+CONNECTED	LITERAL1
+ANY_FUNCTION_CODE	LITERAL1
+READ_COIL	LITERAL1
+READ_DISCR_INPUT	LITERAL1
+READ_HOLD_REGISTER	LITERAL1
+READ_INPUT_REGISTER	LITERAL1
+WRITE_COIL	LITERAL1
+WRITE_HOLD_REGISTER	LITERAL1
+READ_EXCEPTION_SERIAL	LITERAL1
+DIAGNOSTICS_SERIAL	LITERAL1
+READ_COMM_CNT_SERIAL	LITERAL1
+READ_COMM_LOG_SERIAL	LITERAL1
+WRITE_MULT_COILS	LITERAL1
+WRITE_MULT_REGISTERS	LITERAL1
+REPORT_SERVER_ID_SERIAL	LITERAL1
+READ_FILE_RECORD	LITERAL1
+WRITE_FILE_RECORD	LITERAL1
+MASK_WRITE_REGISTER	LITERAL1
+R_W_MULT_REGISTERS	LITERAL1
+READ_FIFO_QUEUE	LITERAL1
+ENCAPSULATED_INTERFACE	LITERAL1
+USER_DEFINED_41	LITERAL1
+USER_DEFINED_42	LITERAL1
+USER_DEFINED_43	LITERAL1
+USER_DEFINED_44	LITERAL1
+USER_DEFINED_45	LITERAL1
+USER_DEFINED_46	LITERAL1
+USER_DEFINED_47	LITERAL1
+USER_DEFINED_48	LITERAL1
+USER_DEFINED_64	LITERAL1
+USER_DEFINED_65	LITERAL1
+USER_DEFINED_66	LITERAL1
+USER_DEFINED_67	LITERAL1
+USER_DEFINED_68	LITERAL1
+USER_DEFINED_69	LITERAL1
+USER_DEFINED_6A	LITERAL1
+USER_DEFINED_6B	LITERAL1
+USER_DEFINED_6C	LITERAL1
+USER_DEFINED_6D	LITERAL1
+USER_DEFINED_6E	LITERAL1
+SUCCESS	LITERAL1
+ILLEGAL_FUNCTION	LITERAL1
+ILLEGAL_DATA_ADDRESS	LITERAL1
+ILLEGAL_DATA_VALUE	LITERAL1
+SERVER_DEVICE_FAILURE	LITERAL1
+ACKNOWLEDGE	LITERAL1
+SERVER_DEVICE_BUSY	LITERAL1
+NEGATIVE_ACKNOWLEDGE	LITERAL1
+MEMORY_PARITY_ERROR	LITERAL1
+GATEWAY_PATH_UNAVAIL	LITERAL1
+GATEWAY_TARGET_NO_RESP	LITERAL1
+TIMEOUT	LITERAL1
+INVALID_SERVER	LITERAL1
+CRC_ERROR	LITERAL1
+FC_MISMATCH	LITERAL1
+SERVER_ID_MISMATCH	LITERAL1
+PACKET_LENGTH_ERROR	LITERAL1
+PARAMETER_COUNT_ERROR	LITERAL1
+PARAMETER_LIMIT_ERROR	LITERAL1
+REQUEST_QUEUE_FULL	LITERAL1
+ILLEGAL_IP_OR_PORT	LITERAL1
+IP_CONNECTION_FAILED	LITERAL1
+TCP_HEAD_MISMATCH	LITERAL1
+EMPTY_MESSAGE	LITERAL1
+ASCII_FRAME_ERR	LITERAL1
+ASCII_CRC_ERR	LITERAL1
+ASCII_INVALID_CHAR	LITERAL1
+BROADCAST_ERROR	LITERAL1
+UNDEFINED_ERROR	LITERAL1
+FC01_TYPE	LITERAL1
+FC07_TYPE	LITERAL1
+FC0F_TYPE	LITERAL1
+FC10_TYPE	LITERAL1
+FC16_TYPE	LITERAL1
+FC18_TYPE	LITERAL1
+FCGENERIC	LITERAL1
+FCUSER	LITERAL1
+FCILLEGAL	LITERAL1
+PrintOut	LITERAL1
+LOG_LEVEL	LITERAL1
+LOCAL_LOG_LEVEL	LITERAL1
+LOG_LEVEL_NONE	LITERAL1
+LOG_LEVEL_CRITICAL	LITERAL1
+LOG_LEVEL_ERROR	LITERAL1
+LOG_LEVEL_WARNING	LITERAL1
+LOG_LEVEL_INFO	LITERAL1
+LOG_LEVEL_DEBUG	LITERAL1
+LOG_LEVEL_VERBOSE	LITERAL1
+LL_RED	LITERAL1
+LL_GREEN	LITERAL1
+LL_YELLOW	LITERAL1
+LL_BLUE	LITERAL1
+LL_MAGENTA	LITERAL1
+LL_CYAN	LITERAL1
+LL_NORM	LITERAL1
+LOG_HEADER	LITERAL1
+LOG_LINE_C	LITERAL1
+LOG_LINE_E	LITERAL1
+LOG_LINE_T	LITERAL1
+LOG_RAW_C	LITERAL1
+LOG_RAW_E	LITERAL1
+LOG_RAW_T	LITERAL1
+HEX_DUMP_T	LITERAL1
+LOG_N	LITERAL1
+LOGRAW_N	LITERAL1
+HEXDUMP_N	LITERAL1
+LOG_C	LITERAL1
+LOGRAW_C	LITERAL1
+HEXDUMP_C	LITERAL1
+LOG_E	LITERAL1
+LOGRAW_E	LITERAL1
+HEXDUMP_E	LITERAL1
+LOG_W	LITERAL1
+LOGRAW_W	LITERAL1
+HEXDUMP_W	LITERAL1
+LOG_I	LITERAL1
+LOGRAW_I	LITERAL1
+HEXDUMP_I	LITERAL1
+LOG_D	LITERAL1
+LOGRAW_D	LITERAL1
+HEXDUMP_D	LITERAL1
+LOG_V	LITERAL1
+LOGRAW_V	LITERAL1
+HEXDUMP_V	LITERAL1
+LOCAL_LOG_LEVEL	LITERAL1
+TCP_SERVER	LITERAL1
+RTU_SERVER	LITERAL1
+SERVER_END	LITERAL1
+LOCAL_LOG_LEVEL	LITERAL1
+DEFAULTTIMEOUT	LITERAL1
+DEFAULTIDLETIME	LITERAL1
+LOCAL_LOG_LEVEL	LITERAL1
+SERVER_END	LITERAL1
+SWAP_BYTES	LITERAL1
+SWAP_REGISTERS	LITERAL1
+SWAP_WORDS	LITERAL1
+SWAP_NIBBLES	LITERAL1
+LOCK_GUARD	LITERAL1
diff --git a/lib/eModbus/library.json b/lib/eModbus/library.json
new file mode 100644
index 000000000..43e9b7e44
--- /dev/null
+++ b/lib/eModbus/library.json
@@ -0,0 +1,46 @@
+{
+  "name": "eModbus",
+  "version": "1.7.0",
+  "keywords": "Arduino, ESP32, Modbus, RTU, ASCII, ModbusASCII, ModbusRTU, ModbusTCP",
+  "description": "ModbusRTU, ModbusASCII and ModbusTCP functions for ESP32",
+  "homepage": "https://emodbus.github.io",
+  "license": "MIT",
+  "authors": [
+    {
+      "name": "Bert Melis",
+      "url": "https://github.com/bertmelis",
+      "maintainer": true
+    },
+    {
+      "name": "Michael Harwerth",
+      "url": "https://github.com/Miq1",
+      "email": "miq1@gmx.de",
+      "maintainer": true
+    }
+  ],
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/eModbus/eModbus",
+    "branch": "master"
+  },
+  "export": {
+    "include":
+    [
+        "src/*.cpp",
+        "src/*.h",
+        "examples/*",
+        "Test/*",
+        ".gitignore",
+        "README.md",
+        "license.md",
+        "keywords.txt",
+        "library.properties",
+        "library.json"
+    ]
+  },
+  "frameworks": "arduino",
+  "platforms": [
+    "espressif32",
+    "espressif8266"
+  ]
+}
diff --git a/lib/eModbus/library.properties b/lib/eModbus/library.properties
new file mode 100644
index 000000000..4143f59eb
--- /dev/null
+++ b/lib/eModbus/library.properties
@@ -0,0 +1,9 @@
+name=eModbus
+version=1.7.0
+author=bertmelis,Miq1 <miq1@gmx.de>
+maintainer=Miq1 <miq1@gmx.de>
+sentence=eModbus provides Modbus RTU, ASCII and TCP functions for ESP32.
+paragraph=This library is non-blocking for the program using it. Modbus requests and responses will be returned to user-supplied callback functions. All Modbus function codes are supported implicitly, the codes specified by the Modbus specs are parameter-checked.
+category=Communication
+url=https://github.com/eModbus/eModbus
+architectures=esp32,FreeRTOS
diff --git a/lib/eModbus/license.md b/lib/eModbus/license.md
new file mode 100644
index 000000000..69d50d61b
--- /dev/null
+++ b/lib/eModbus/license.md
@@ -0,0 +1,7 @@
+#### Copyright 2020 Michael Harwerth, Bert Melis and the contributors to eModbus (MIT license)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+#### The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
diff --git a/lib/eModbus/src/CoilData.cpp b/lib/eModbus/src/CoilData.cpp
new file mode 100644
index 000000000..8348080d5
--- /dev/null
+++ b/lib/eModbus/src/CoilData.cpp
@@ -0,0 +1,554 @@
+// =================================================================================================
+// eModbus: Copyright 2020, 2021 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+
+#include "CoilData.h"
+#undef LOCAL_LOG_LEVEL
+#include "Logging.h"
+
+// Constructor: optional size in bits, optional initial value for all bits
+// Maximum size is 2000 coils (=250 bytes)
+CoilData::CoilData(uint16_t size, bool initValue) :
+  CDsize(0),
+  CDbyteSize(0), 
+  CDbuffer(nullptr) {
+  // Limit the size to 2000 (Modbus rules)
+  if (size > 2000) size = 2000;
+  // Do we have a size?
+  if (size) {
+    // Calculate number of bytes needed
+    CDbyteSize = byteIndex(size - 1) + 1;
+    // Allocate and init buffer
+    CDbuffer = new uint8_t[CDbyteSize];
+    memset(CDbuffer, initValue ? 0xFF : 0, CDbyteSize);
+    if (initValue) {
+      CDbuffer[CDbyteSize - 1] &= CDfilter[bitIndex(size - 1)];
+    }
+    CDsize = size;
+  }
+}
+
+// Alternate constructor, taking a "1101..." bit image char array to init
+CoilData::CoilData(const char *initVector) :
+  CDsize(0),
+  CDbyteSize(0), 
+  CDbuffer(nullptr) {
+  // Init with bit image array. 
+  setVector(initVector);
+}
+
+// Destructor: take care of cleaning up
+CoilData::~CoilData() {
+  if (CDbuffer) {
+    delete CDbuffer;
+  }
+}
+
+// Assignment operator
+CoilData& CoilData::operator=(const CoilData& m) {
+  // Remove old data
+  if (CDbuffer) {
+    delete CDbuffer;
+  }
+  // Are coils in source?
+  if (m.CDsize > 0) {
+    // Yes. Allocate new buffer and copy data
+    CDbuffer = new uint8_t[m.CDbyteSize];
+    memcpy(CDbuffer, m.CDbuffer, m.CDbyteSize);
+    CDsize = m.CDsize;
+    CDbyteSize = m.CDbyteSize;
+  } else {
+    // No, leave buffer empty
+    CDsize = 0;
+    CDbyteSize = 0;
+    CDbuffer = nullptr;
+  }
+  return *this;
+}
+
+// Copy constructor
+CoilData::CoilData(const CoilData& m) :
+  CDsize(0),
+  CDbyteSize(0), 
+  CDbuffer(nullptr) {
+  // Has the source coils at all?
+  if (m.CDsize > 0) {
+    // Yes. Allocate new buffer and copy data
+    CDbuffer = new uint8_t[m.CDbyteSize];
+    memcpy(CDbuffer, m.CDbuffer, m.CDbyteSize);
+    CDsize = m.CDsize;
+    CDbyteSize = m.CDbyteSize;
+  }
+}
+
+#ifndef NO_MOVE
+// Move constructor
+CoilData::CoilData(CoilData&& m) {
+  // Copy all data
+  CDbuffer = m.CDbuffer;
+  CDsize = m.CDsize;
+  CDbyteSize = m.CDbyteSize;
+  // Then clear source
+  m.CDbuffer = nullptr;
+  m.CDsize = 0;
+  m.CDbyteSize = 0;
+}
+
+// Move assignment
+CoilData& CoilData::operator=(CoilData&& m) {
+  // Remove buffer, if already allocated
+  if (CDbuffer) {
+    delete CDbuffer;
+  }
+  // Are there coils in the source at all?
+  if (m.CDsize > 0) {
+    // Yes. Copy over all data
+    CDbuffer = m.CDbuffer;
+    CDsize = m.CDsize;
+    CDbyteSize = m.CDbyteSize;
+    // Then clear source
+    m.CDbuffer = nullptr;
+    m.CDsize = 0;
+    m.CDbyteSize = 0;
+  } else {
+    // No, leave object empty.
+    CDbuffer = nullptr;
+    CDsize = 0;
+    CDbyteSize = 0;
+  }
+  return *this;
+}
+#endif
+
+// Comparison operators
+bool CoilData::operator==(const CoilData& m) {
+  // Self-compare is always true
+  if (this == &m) return true;
+  // Different sizes are never equal
+  if (CDsize != m.CDsize) return false;
+  // Compare the data
+  if (CDsize > 0 && memcmp(CDbuffer, m.CDbuffer, CDbyteSize)) return false;
+  return true;
+}
+
+// Inequality: invert the result of the equality comparison
+bool CoilData::operator!=(const CoilData& m) {
+  return !(*this == m);
+}
+
+// Assignment of a bit image char array to re-init
+CoilData& CoilData::operator=(const char *initVector) {
+  // setVector() may be unsuccessful - then data is deleted!
+  setVector(initVector);
+  return *this;
+}
+
+// If used as vector<uint8_t>, return a complete slice
+CoilData::operator vector<uint8_t> const () {
+  // Create new vector to return
+  vector<uint8_t> retval;
+  if (CDsize > 0) {
+    // Copy over all buffer content
+      retval.assign(CDbuffer, CDbuffer + CDbyteSize);
+  }
+  // return the copy (or an empty vector)
+  return retval;
+}
+
+// slice: return a CoilData object with coils shifted leftmost
+// will return empty object if illegal parameters are detected
+CoilData CoilData::slice(uint16_t start, uint16_t length) {
+  CoilData retval;
+
+  // Any slice of an empty coilset is an empty coilset ;)
+  if (CDsize == 0) return retval;
+
+  // If start is beyond the available coils, return empty slice
+  if (start > CDsize) return retval;
+
+  // length default is all up to the end
+  if (length == 0) length = CDsize - start;
+
+  // Does the requested slice fit in the buffer?
+  if ((start + length) <= CDsize) {
+    // Yes, it does. Extend return object
+    retval = CoilData(length);
+
+  // Loop over all requested bits
+    for (uint16_t i = start; i < start + length; ++i) {
+      if (CDbuffer[byteIndex(i)] & (1 << bitIndex(i))) {
+        retval.set(i - start, true);
+      }
+    }
+  }
+  return retval;
+}
+
+// operator[]: return value of a single coil
+bool CoilData::operator[](uint16_t index) const {
+  if (index < CDsize) {
+    return (CDbuffer[byteIndex(index)] & (1 << bitIndex(index))) ? true : false;
+  }
+  // Wrong parameter -> always return false
+  return false;
+}
+
+// set functions to change coil value(s)
+// Will return true if done, false if impossible (wrong address or data)
+
+// set #1: alter one single coil
+bool CoilData::set(uint16_t index, bool value) {
+  // Within coils?
+  if (index < CDsize) {
+    // Yes. Determine affected byte and bit therein
+    uint16_t by = byteIndex(index);
+    uint8_t mask = 1 << bitIndex(index);
+
+    // Stamp out bit
+    CDbuffer[by] &= ~mask;
+    // If required, set it to 1 now
+    if (value) {
+      CDbuffer[by] |= mask;
+    }
+    return true;
+  }
+  // Wrong parameter -> always return false
+  return false;
+}
+
+// set #2: alter a group of coils, overwriting it by the bits from vector newValue
+bool CoilData::set(uint16_t start, uint16_t length, vector<uint8_t> newValue) {
+  // Does the vector contain enough data for the specified size?
+  if (newValue.size() >= (size_t)(byteIndex(length - 1) + 1)) {
+    // Yes, we safely may call set #3 with it
+    return set(start, length, newValue.data());
+  }
+  return false;
+}
+
+// set #3: alter a group of coils, overwriting it by the bits from uint8_t buffer newValue
+// **** Watch out! ****
+// This may be a potential risk if newValue is pointing to an array shorter than required. 
+// Then heap data behind the array may be used to set coils!
+bool CoilData::set(uint16_t start, uint16_t length, uint8_t *newValue) {
+  // Does the requested slice fit in the buffer?
+  if (length && (start + length) <= CDsize) {
+    // Yes, it does. 
+    // Prepare pointers to the source byte and the bit within
+    uint8_t *cp = newValue;
+    uint8_t bitPtr = 0;
+
+    // Loop over all bits to be set
+    for (uint16_t i = start; i < start + length; i++) {
+      // Get affected byte
+      uint8_t by = byteIndex(i);
+      // Calculate single-bit mask in target byte
+      uint8_t mask = 1 << bitIndex(i);
+      // Stamp out bit
+      CDbuffer[by] &= ~mask;
+      // is source bit set?
+      if (*cp & (1 << bitPtr)) {
+        // Yes. Set it in target as well
+        CDbuffer[by] |= mask;
+      }
+      // Advance source bit ptr
+      bitPtr++;
+      // Overflow?
+      if (bitPtr >= 8) {
+        // Yes. move pointers to first bit in next source byte
+        bitPtr = 0;
+        cp++;
+      }
+    }
+    return true;
+  }
+  return false;
+}
+
+// set #4: alter a group of coils, overwriting it by the coils in another CoilData object
+// Setting stops when either target storage or source coils are exhausted
+bool CoilData::set(uint16_t index, const CoilData& c) {
+  // if source object is empty, return false
+  if (c.empty()) return false;
+
+  // If target is empty, or index is beyond coils, return false
+  if (CDsize == 0 || index >= CDsize) return false;
+
+  // Take the minimum of remaining coils after index and the length of c
+  uint16_t length = CDsize - index;
+  if (c.coils() < length) length = c.coils();
+
+  // Loop over all coils to be copied
+  for (uint16_t i = index; i < index + length; ++i) {
+    set(i, c[i - index]);
+  }
+  return true;
+}
+
+// set #5: alter a group of coils, overwriting it by a bit image array
+// Setting stops when either target storage or source bits are exhausted
+bool CoilData::set(uint16_t index, const char *initVector) {
+  // if target is empty or index is beyond coils, return false
+  if (CDsize == 0 || index >= CDsize) return false;
+
+  // We do a single pass on the bit image array, until it ends or the target is exhausted
+  const char *cp = initVector;   // pointer to source array
+  bool skipFlag = false;         // Signal next character irrelevant
+
+  while (*cp && index < CDsize) {
+    switch (*cp) {
+    case '1':  // A valid 1 bit
+    case '0':  // A valid 0 bit
+      // Shall we ignore it?
+      if (skipFlag) {
+        // Yes. just reset the ignore flag
+        skipFlag = false;
+      } else {
+        // No, we can set it. First stamp out the existing bit
+        CDbuffer[byteIndex(index)] &= ~(1 << bitIndex(index));
+        // Do we have a 1 bit here?
+        if (*cp == '1') {
+          // Yes. set it in coil storage
+          CDbuffer[byteIndex(index)] |= (1 << bitIndex(index));
+        }
+        index++;
+      }
+      break;
+    case '_':  // Skip next
+      skipFlag = true;
+      break;
+    default:  // anything else
+      skipFlag = false;
+      break;
+    }
+    cp++;
+  }
+  return true;
+}
+
+// Comparison against bit image array
+bool CoilData::operator==(const char *initVector) {
+  const char *cp = initVector;   // pointer to source array
+  bool skipFlag = false;         // Signal next character irrelevant
+  uint16_t index = 0;
+
+  // We do a single pass on the bit image array, until it ends or the target is exhausted
+  while (*cp && index < CDsize) {
+    switch (*cp) {
+    case '1':  // A valid 1 bit
+    case '0':  // A valid 0 bit
+      // Shall we ignore it?
+      if (skipFlag) {
+        // Yes. just reset the ignore flag
+        skipFlag = false;
+      } else {
+        // No, we can compare it
+        uint8_t value = CDbuffer[byteIndex(index)] & (1 << bitIndex(index));
+        // Do we have a 1 bit here?
+        if (*cp == '1') {
+          // Yes. Is the source different? Then we can stop
+          if (value == 0) return false;
+        } else {
+          // No, it is a 0. Different?
+          if (value) return false;
+        }
+        index++;
+      }
+      break;
+    case '_':  // Skip next
+      skipFlag = true;
+      break;
+    default:  // anything else
+      skipFlag = false;
+      break;
+    }
+    cp++;
+  }
+  // So far everything was equal, but we may have more bits in the image array!
+  if (*cp) {
+    // There is more. Check for more valid bits
+    while (*cp) {
+      switch (*cp) {
+      case '1':  // A valid 1 bit
+      case '0':  // A valid 0 bit
+        // Shall we ignore it?
+        if (skipFlag) {
+          // Yes. just reset the ignore flag
+          skipFlag = false;
+        } else {
+          // No, a valid bit that exceeds the target coils count
+          return false;
+        }
+        break;
+      case '_':  // Skip next
+        skipFlag = true;
+        break;
+      default:  // anything else
+        skipFlag = false;
+        break;
+      }
+      cp++;
+    }
+  }
+  return true;
+}
+
+bool CoilData::operator!=(const char *initVector) {
+  return !(*this == initVector);
+}
+
+// Init all coils by a readable bit image array
+bool CoilData::setVector(const char *initVector) {
+  uint16_t length = 0;           // resulting bit pattern length
+  const char *cp = initVector;   // pointer to source array
+  bool skipFlag = false;         // Signal next character irrelevant
+
+  // Do a first pass to count all valid bits in array
+  while (*cp) {
+    switch (*cp) {
+    case '1':  // A valid 1 bit
+    case '0':  // A valid 0 bit
+      // Shall we ignore it?
+      if (skipFlag) {
+        // Yes. just reset the ignore flag
+        skipFlag = false;
+      } else {
+        // No, we can count it
+        length++;
+      }
+      break;
+    case '_':  // Skip next
+      skipFlag = true;
+      break;
+    default:  // anything else
+      skipFlag = false;
+      break;
+    }
+    cp++;
+  }
+
+  // If there are coils already, trash them.
+  if (CDbuffer) {
+    delete CDbuffer;
+  }
+  CDsize = 0;
+  CDbyteSize = 0;
+
+  // Did we count a manageable number?
+  if (length && length <= 2000) {
+    // Yes. Init the coils
+    CDsize = length;
+    CDbyteSize = byteIndex(length - 1) + 1;
+    // Allocate new coil storage
+    CDbuffer = new uint8_t[CDbyteSize];
+    memset(CDbuffer, 0, CDbyteSize);
+
+    // Prepare second loop
+    uint16_t ptr = 0;    // bit pointer in coil storage
+    skipFlag = false;
+    cp = initVector;
+
+    // Do a second pass, converting 1 and 0 into coils (bits)
+    // loop as above, only difference is setting the bits
+    while (*cp) {
+      switch (*cp) {
+      case '1':
+      case '0':
+        if (skipFlag) {
+          skipFlag = false;
+        } else {
+          // Do we have a 1 bit here?
+          if (*cp == '1') {
+            // Yes. set it in coil storage
+            CDbuffer[byteIndex(ptr)] |= (1 << bitIndex(ptr));
+          }
+          // advance bit pointer in any case 0 or 1
+          ptr++;
+        }
+        break;
+      case '_':
+        skipFlag = true;
+        break;
+      default:
+        skipFlag = false;
+        break;
+      }
+      cp++;
+    }
+    // We had content, so return true
+    return true;
+  }
+  // No valid bits found, return false 
+  return false;
+}
+
+// init: set all coils to 1 or 0 (default)
+void CoilData::init(bool value) {
+  if (CDsize > 0) {
+    memset(CDbuffer, value ? 0xFF : 0, CDbyteSize);
+    // Stamp out overhang bits
+    CDbuffer[CDbyteSize - 1] &= CDfilter[bitIndex(CDsize - 1)];
+  }
+}
+
+// Return number of coils set to 1 (or not)
+// Uses Brian Kernighan's algorithm!
+uint16_t CoilData::coilsSetON() const {
+  uint16_t count = 0;
+
+  // Do we have coils at all?
+  if (CDbyteSize) {
+    // Yes. Loop over all bytes summing up the '1' bits
+    for (uint8_t i = 0; i < CDbyteSize; ++i) {
+      uint8_t by = CDbuffer[i];
+      while (by) {
+        by &= by - 1; // this clears the LSB-most set bit
+        count++;
+      }
+    }
+  }
+  return count;
+}
+
+uint16_t CoilData::coilsSetOFF() const {
+  return CDsize - coilsSetON();
+}
+
+#if !IS_LINUX
+// Not for Linux for the Print reference!
+
+// Print out a coil storage in readable form to ease debugging
+void CoilData::print(const char *label, Print& s) {
+  uint8_t bitptr = 0;
+  uint8_t labellen = strlen(label);
+  uint8_t pos = labellen;
+
+  // Put out the label
+  s.print(label);
+
+  // Print out all coils as "1" or "0"
+  for (uint16_t i = 0; i < CDsize; ++i) {
+    s.print((CDbuffer[byteIndex(i)] & (1 << bitptr)) ? "1" : "0");
+    pos++;
+    // Have a blank after every group of 4
+    if (i % 4 == 3) {
+      // Have a line break if > 80 characters, including the last group of 4
+      if (pos >= 80) {
+        s.println("");
+        pos = 0;
+        // Leave a nice empty space below the label
+        while (pos++ < labellen) {
+          s.print(" ");
+        }
+      } else {
+        s.print(" ");
+        pos++;
+      }
+    }
+    bitptr++;
+    bitptr &= 0x07;
+  }
+  s.println("");
+}
+#endif
diff --git a/lib/eModbus/src/CoilData.h b/lib/eModbus/src/CoilData.h
new file mode 100644
index 000000000..fe01618a9
--- /dev/null
+++ b/lib/eModbus/src/CoilData.h
@@ -0,0 +1,122 @@
+// =================================================================================================
+// eModbus: Copyright 2020, 2021 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+
+#ifndef _COILDATA_H
+#define _COILDATA_H
+
+#include <vector>
+#include <cstdint>
+#include "options.h"
+
+using std::vector;
+
+// CoilData: representing Modbus coil (=bit) values
+class CoilData {
+public:
+  // Constructor: optional size in bits, optional initial value for all bits
+  // Maximum size is 2000 coils (=250 bytes)
+  explicit CoilData(uint16_t size = 0, bool initValue = false);
+
+  // Alternate constructor, taking a "1101..." bit image char array to init
+  explicit CoilData(const char *initVector);
+
+  // Destructor: take care of cleaning up
+  ~CoilData();
+
+  // Assignment operator
+  CoilData& operator=(const CoilData& m);
+  
+  // Copy constructor
+  CoilData(const CoilData& m);
+
+#ifndef NO_MOVE
+  // Move constructor
+	CoilData(CoilData&& m);
+  
+	// Move assignment
+	CoilData& operator=(CoilData&& m);
+#endif
+
+  // Comparison operators
+  bool operator==(const CoilData& m);
+  bool operator!=(const CoilData& m);
+  bool operator==(const char *initVector);
+  bool operator!=(const char *initVector);
+
+  // Assignment of a bit image char array to re-init
+  CoilData& operator=(const char *initVector);
+
+  // If used as vector<uint8_t>, return the complete set
+  operator vector<uint8_t> const ();
+
+  // slice: return a new CoilData object with coils shifted leftmost
+  // will return empty set if illegal parameters are detected
+  // Default start is first coil, default length all to the end
+  CoilData slice(uint16_t start = 0, uint16_t length = 0);
+
+  // operator[]: return value of a single coil
+  bool operator[](uint16_t index) const;
+
+  // Set functions to change coil value(s)
+  // Will return true if done, false if impossible (wrong address or data)
+
+  // set #1: alter one single coil
+  bool set(uint16_t index, bool value);
+
+  // set #2: alter a group of coils, overwriting it by the bits from newValue
+  bool set(uint16_t index, uint16_t length, vector<uint8_t> newValue);
+
+  // set #3: alter a group of coils, overwriting it by the bits from unit8_t buffer newValue
+  bool set(uint16_t index, uint16_t length, uint8_t *newValue);
+
+  // set #4: alter a group of coils, overwriting it by the coils in another CoilData object
+  // Setting stops when either target storage or source coils are exhausted
+  bool set(uint16_t index, const CoilData& c);
+
+  // set #5: alter a group of coils, overwriting it by a bit image array
+  // Setting stops when either target storage or source bits are exhausted
+  bool set(uint16_t index, const char *initVector);
+
+  // (Re-)init complete coil set to 1 or 0
+  void init(bool value = false);
+
+  // get size in coils
+  inline uint16_t coils() const { return CDsize; }
+
+  // Raw access to coil data buffer
+  inline uint8_t *data() const { return CDbuffer; };
+  inline uint8_t size() const { return CDbyteSize; };
+
+  // Test if there are any coils in object
+  inline bool empty() const { return (CDsize >0) ? true : false; }
+  inline operator bool () const { return empty(); }
+
+  // Return number of coils set to 1 (or ON)
+  uint16_t coilsSetON() const;
+  // Return number of coils set to 0 (or OFF)
+  uint16_t coilsSetOFF() const;
+
+#if !LINUX
+  // Helper function to dump out coils in logical order
+  void print(const char *label, Print& s);
+#endif
+
+protected:
+  // bit masks for bits left of a bit index in a byte
+  const uint8_t CDfilter[8] = { 0x01, 0x03, 0x07, 0x0F, 0x1F, 0x3F, 0x7F, 0xFF };
+  // Calculate byte index and bit index within that byte
+  inline uint8_t byteIndex(uint16_t index) const { return index >> 3; }
+  inline uint8_t bitIndex(uint16_t index) const { return index & 0x07; }
+  // Calculate reversed bit sequence for a byte (taken from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith32Bits)
+  inline uint8_t reverseBits(uint8_t b) { return ((b * 0x0802LU & 0x22110LU) | (b * 0x8020LU & 0x88440LU)) * 0x10101LU >> 16; }
+  // (Re-)init with bit image vector
+  bool setVector(const char *initVector);
+
+  uint16_t CDsize;         // Size of the CoilData store in bits
+  uint8_t  CDbyteSize;     // Size in bytes
+  uint8_t *CDbuffer;       // Pointer to bit storage
+};
+
+#endif
diff --git a/lib/eModbus/src/Logging.cpp b/lib/eModbus/src/Logging.cpp
new file mode 100644
index 000000000..1991cfad1
--- /dev/null
+++ b/lib/eModbus/src/Logging.cpp
@@ -0,0 +1,68 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "Logging.h"
+#include <cinttypes>
+
+int MBUlogLvl = LOG_LEVEL;
+#if IS_LINUX
+#define PrintOut printf
+
+void logHexDump(const char *letter, const char *label, const uint8_t *data, const size_t length) {
+#else
+Print *LOGDEVICE = &Serial;
+#define PrintOut output->printf
+
+void logHexDump(Print *output, const char *letter, const char *label, const uint8_t *data, const size_t length) {
+#endif
+  size_t cnt = 0;
+  size_t step = 0;
+  char limiter = '|';
+  // Use line buffer to speed up output
+  const uint16_t BUFLEN(80);
+  const uint16_t ascOffset(61);
+  char linebuf[BUFLEN];
+  char *cp = linebuf;
+  const char HEXDIGIT[] = "0123456789ABCDEF";
+
+  // Print out header
+  PrintOut ("[%s] %s: @%" PRIXPTR "/%" PRIu32 ":\n", letter, label, (uintptr_t)data, (uint32_t)(length & 0xFFFFFFFF));
+
+  // loop over data in steps of 16
+  for (cnt = 0; cnt < length; ++cnt) {
+    step = cnt % 16;
+    // New line?
+    if (step == 0) {
+      // Yes. Clear line and print address header
+      memset(linebuf, ' ', BUFLEN);
+      linebuf[60] = limiter;
+      linebuf[77] = limiter;
+      linebuf[78] = '\n';
+      linebuf[BUFLEN - 1] = 0;
+      snprintf(linebuf, BUFLEN, "  %c %04X: ", limiter, (uint16_t)(cnt & 0xFFFF));
+      cp = linebuf + strlen(linebuf);
+      // No, but first block of 8 done?
+    } else if (step == 8) {
+      // Yes, put out additional space
+      cp++;
+    }
+    // Print data byte
+    uint8_t c = data[cnt];
+    *cp++ = HEXDIGIT[(c >> 4) & 0x0F];
+    *cp++ = HEXDIGIT[c & 0x0F];
+    *cp++ = ' ';
+    if (c >= 32 && c <= 127) linebuf[ascOffset + step] = c;
+    else                     linebuf[ascOffset + step] = '.';
+    // Line end?
+    if (step == 15) {
+      // Yes, print line
+      PrintOut ("%s", linebuf);
+    }
+  }
+  // Unfinished line?
+  if (length && step != 15) {
+      // Yes, print line
+      PrintOut ("%s", linebuf);
+  }
+}
diff --git a/lib/eModbus/src/Logging.h b/lib/eModbus/src/Logging.h
new file mode 100644
index 000000000..88b1cb8b2
--- /dev/null
+++ b/lib/eModbus/src/Logging.h
@@ -0,0 +1,181 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+
+#ifndef LOG_LEVEL
+#define LOG_LEVEL LOG_LEVEL_ERROR
+#endif
+
+#ifndef LOCAL_LOG_LEVEL
+#define LOCAL_LOG_LEVEL LOG_LEVEL
+#endif
+
+// The following needs to be defined only once
+#ifndef _MODBUS_LOGGING
+#define _MODBUS_LOGGING
+#include "options.h"
+
+#define LOG_LEVEL_NONE (0)
+#define LOG_LEVEL_CRITICAL (1)
+#define LOG_LEVEL_ERROR (2)
+#define LOG_LEVEL_WARNING (3)
+#define LOG_LEVEL_INFO (4)
+#define LOG_LEVEL_DEBUG (5)
+#define LOG_LEVEL_VERBOSE (6)
+
+#define LL_RED "\e[1;31m"
+#define LL_GREEN "\e[32m"
+#define LL_YELLOW "\e[1;33m"
+#define LL_BLUE "\e[34m"
+#define LL_MAGENTA "\e[35m"
+#define LL_CYAN "\e[36m"
+#define LL_NORM "\e[0m"
+
+#define LOG_HEADER(x) "[" #x "] %lu| %-20s [%4d] %s: "
+
+constexpr const char* str_end(const char *str) {
+    return *str ? str_end(str + 1) : str;
+}
+
+constexpr bool str_slant(const char *str) {
+    return ((*str == '/') || (*str == '\\')) ? true : (*str ? str_slant(str + 1) : false);
+}
+
+constexpr const char* r_slant(const char* str) {
+    return ((*str == '/') || (*str == '\\')) ? (str + 1) : r_slant(str - 1);
+}
+constexpr const char* file_name(const char* str) {
+    return str_slant(str) ? r_slant(str_end(str)) : str;
+}
+
+#if IS_LINUX
+void logHexDump(const char *letter, const char *label, const uint8_t *data, const size_t length);
+#else
+extern Print *LOGDEVICE;
+void logHexDump(Print *output, const char *letter, const char *label, const uint8_t *data, const size_t length);
+#endif
+extern int MBUlogLvl;
+#endif  // _MODBUS_LOGGING
+
+// The remainder may need to be redefined if LOCAL_LOG_LEVEL was set differently before
+#ifdef LOG_LINE_T
+#undef LOG_LINE_C
+#undef LOG_LINE_E
+#undef LOG_LINE_T
+#undef LOG_RAW_C
+#undef LOG_RAW_E
+#undef LOG_RAW_T
+#undef HEX_DUMP_T
+#undef LOG_N
+#undef LOG_C
+#undef LOG_E
+#undef LOG_W
+#undef LOG_I
+#undef LOG_D
+#undef LOG_V
+#undef LOGRAW_N
+#undef LOGRAW_C
+#undef LOGRAW_E
+#undef LOGRAW_W
+#undef LOGRAW_I
+#undef LOGRAW_D
+#undef LOGRAW_V
+#undef HEXDUMP_N
+#undef HEXDUMP_C
+#undef HEXDUMP_E
+#undef HEXDUMP_W
+#undef HEXDUMP_I
+#undef HEXDUMP_D
+#undef HEXDUMP_V
+#endif
+
+// Now we can define the macros based on LOCAL_LOG_LEVEL
+#if IS_LINUX
+#define LOG_LINE_C(level, x, format, ...) if (MBUlogLvl >= level) printf(LL_RED LOG_HEADER(x) format LL_NORM, millis(), file_name(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+#define LOG_LINE_E(level, x, format, ...) if (MBUlogLvl >= level) printf(LL_YELLOW LOG_HEADER(x) format LL_NORM, millis(), file_name(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+#define LOG_LINE_T(level, x, format, ...) if (MBUlogLvl >= level) printf(LOG_HEADER(x) format, millis(), file_name(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+#define LOG_RAW_C(level, x, format, ...) if (MBUlogLvl >= level) printf(LL_RED format LL_NORM, ##__VA_ARGS__)
+#define LOG_RAW_E(level, x, format, ...) if (MBUlogLvl >= level) printf(LL_YELLOW format LL_NORM, ##__VA_ARGS__)
+#define LOG_RAW_T(level, x, format, ...) if (MBUlogLvl >= level) printf(format, ##__VA_ARGS__)
+#define HEX_DUMP_T(x, level, label, address, length) if (MBUlogLvl >= level) logHexDump(#x, label, address, length)
+#else
+#define LOG_LINE_C(level, x, format, ...) if (MBUlogLvl >= level) LOGDEVICE->printf(LL_RED LOG_HEADER(x) format LL_NORM, millis(), file_name(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+#define LOG_LINE_E(level, x, format, ...) if (MBUlogLvl >= level) LOGDEVICE->printf(LL_YELLOW LOG_HEADER(x) format LL_NORM, millis(), file_name(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+#define LOG_LINE_T(level, x, format, ...) if (MBUlogLvl >= level) LOGDEVICE->printf(LOG_HEADER(x) format, millis(), file_name(__FILE__), __LINE__, __func__, ##__VA_ARGS__)
+#define LOG_RAW_C(level, x, format, ...) if (MBUlogLvl >= level) LOGDEVICE->printf(LL_RED format LL_NORM, ##__VA_ARGS__)
+#define LOG_RAW_E(level, x, format, ...) if (MBUlogLvl >= level) LOGDEVICE->printf(LL_YELLOW format LL_NORM, ##__VA_ARGS__)
+#define LOG_RAW_T(level, x, format, ...) if (MBUlogLvl >= level) LOGDEVICE->printf(format, ##__VA_ARGS__)
+#define HEX_DUMP_T(x, level, label, address, length) if (MBUlogLvl >= level) logHexDump(LOGDEVICE, #x, label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_NONE
+#define LOG_N(format, ...) LOG_LINE_T(LOG_LEVEL_NONE, N, format, ##__VA_ARGS__)
+#define LOGRAW_N(format, ...) LOG_RAW_T(LOG_LEVEL_NONE, N, format, ##__VA_ARGS__)
+#define HEXDUMP_N(label, address, length) HEX_DUMP_T(N, LOG_LEVEL_NONE, label, address, length)
+#else
+#define LOG_N(format, ...)
+#define LOGRAW_N(format, ...)
+#define HEXDUMP_N(label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_CRITICAL
+#define LOG_C(format, ...) LOG_LINE_C(LOG_LEVEL_CRITICAL, C, format, ##__VA_ARGS__)
+#define LOGRAW_C(format, ...) LOG_RAW_C(LOG_LEVEL_CRITICAL, C, format, ##__VA_ARGS__)
+#define HEXDUMP_C(label, address, length) HEX_DUMP_T(C, LOG_LEVEL_CRITICAL, label, address, length)
+#else
+#define LOG_C(format, ...)
+#define LOGRAW_C(format, ...)
+#define HEXDUMP_C(label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_ERROR
+#define LOG_E(format, ...) LOG_LINE_E(LOG_LEVEL_ERROR, E, format, ##__VA_ARGS__)
+#define LOGRAW_E(format, ...) LOG_RAW_E(LOG_LEVEL_ERROR, E, format, ##__VA_ARGS__)
+#define HEXDUMP_E(label, address, length) HEX_DUMP_T(E, LOG_LEVEL_ERROR, label, address, length)
+#else
+#define LOG_E(format, ...)
+#define LOGRAW_E(format, ...)
+#define HEXDUMP_E(label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_WARNING
+#define LOG_W(format, ...) LOG_LINE_T(LOG_LEVEL_WARNING, W, format, ##__VA_ARGS__)
+#define LOGRAW_W(format, ...) LOG_RAW_T(LOG_LEVEL_WARNING, W, format, ##__VA_ARGS__)
+#define HEXDUMP_W(label, address, length) HEX_DUMP_T(W, LOG_LEVEL_WARNING, label, address, length)
+#else
+#define LOG_W(format, ...)
+#define LOGRAW_W(format, ...)
+#define HEXDUMP_W(label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_INFO
+#define LOG_I(format, ...) LOG_LINE_T(LOG_LEVEL_INFO, I, format, ##__VA_ARGS__)
+#define LOGRAW_I(format, ...) LOG_RAW_T(LOG_LEVEL_INFO, I, format, ##__VA_ARGS__)
+#define HEXDUMP_I(label, address, length) HEX_DUMP_T(I, LOG_LEVEL_INFO, label, address, length)
+#else
+#define LOG_I(format, ...)
+#define LOGRAW_I(format, ...)
+#define HEXDUMP_I(label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_DEBUG
+#define LOG_D(format, ...) LOG_LINE_T(LOG_LEVEL_DEBUG, D, format, ##__VA_ARGS__)
+#define LOGRAW_D(format, ...) LOG_RAW_T(LOG_LEVEL_DEBUG, D, format, ##__VA_ARGS__)
+#define HEXDUMP_D(label, address, length) HEX_DUMP_T(D, LOG_LEVEL_DEBUG, label, address, length)
+#else
+#define LOG_D(format, ...)
+#define LOGRAW_D(format, ...)
+#define HEXDUMP_D(label, address, length)
+#endif
+
+#if LOCAL_LOG_LEVEL >= LOG_LEVEL_VERBOSE
+#define LOG_V(format, ...) LOG_LINE_T(LOG_LEVEL_VERBOSE, V, format, ##__VA_ARGS__)
+#define LOGRAW_V(format, ...) LOG_RAW_T(LOG_LEVEL_VERBOSE, V, format, ##__VA_ARGS__)
+#define HEXDUMP_V(label, address, length) HEX_DUMP_T(V, LOG_LEVEL_VERBOSE, label, address, length)
+#else
+#define LOG_V(format, ...)
+#define LOGRAW_V(format, ...)
+#define HEXDUMP_V(label, address, length)
+#endif
+
diff --git a/lib/eModbus/src/ModbusBridgeEthernet.h b/lib/eModbus/src/ModbusBridgeEthernet.h
new file mode 100644
index 000000000..3da5db4d4
--- /dev/null
+++ b/lib/eModbus/src/ModbusBridgeEthernet.h
@@ -0,0 +1,21 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_BRIDGE_ETHERNET_H
+#define _MODBUS_BRIDGE_ETHERNET_H
+#include "options.h"
+#if HAS_ETHERNET == 1
+#include <Ethernet.h>
+#include <SPI.h>
+
+#undef SERVER_END
+#define SERVER_END // NIL for Ethernet
+
+#include "ModbusServerTCPtemp.h"
+#include "ModbusBridgeTemp.h"
+
+using ModbusBridgeEthernet = ModbusBridge<ModbusServerTCP<EthernetServer, EthernetClient>>;
+#endif
+
+#endif
diff --git a/lib/eModbus/src/ModbusBridgeRTU.h b/lib/eModbus/src/ModbusBridgeRTU.h
new file mode 100644
index 000000000..6d6d53571
--- /dev/null
+++ b/lib/eModbus/src/ModbusBridgeRTU.h
@@ -0,0 +1,14 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_BRIDGE_RTU_H
+#define _MODBUS_BRIDGE_RTU_H
+#include "options.h"
+#include "ModbusServerRTU.h"
+#include "ModbusBridgeTemp.h"
+#include "RTUutils.h"
+
+using ModbusBridgeRTU = ModbusBridge<ModbusServerRTU>;
+
+#endif
diff --git a/lib/eModbus/src/ModbusBridgeTemp.h b/lib/eModbus/src/ModbusBridgeTemp.h
new file mode 100644
index 000000000..31aa2e0ba
--- /dev/null
+++ b/lib/eModbus/src/ModbusBridgeTemp.h
@@ -0,0 +1,199 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_BRIDGE_TEMP_H
+#define _MODBUS_BRIDGE_TEMP_H
+
+#include <map>
+#include <functional>
+#include "ModbusClient.h"
+#include "ModbusClientTCP.h"  // Needed for client.setTarget()
+#include "RTUutils.h"  // Needed for RTScallback
+
+#undef LOCAL_LOG_LEVEL
+#define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+#include "Logging.h"
+
+using std::bind;
+using std::placeholders::_1;
+
+// Known server types: TCP (client, host/port) and RTU (client)
+enum ServerType : uint8_t { TCP_SERVER, RTU_SERVER };
+
+// Bridge class template, takes one of ModbusServerRTU, ModbusServerWiFi, ModbusServerEthernet or ModbusServerTCPasync as parameter
+template<typename SERVERCLASS>
+class ModbusBridge : public SERVERCLASS {
+public:
+  // Constructor for TCP server variants.
+  ModbusBridge();
+
+  // Constructors for the RTU variant. Parameters as are for ModbusServerRTU
+  ModbusBridge(HardwareSerial& serial, uint32_t timeout, int rtsPin = -1);
+  ModbusBridge(HardwareSerial& serial, uint32_t timeout, RTScallback rts);
+
+  // Destructor
+  ~ModbusBridge();
+
+  // Method to link external servers to the bridge
+  bool attachServer(uint8_t aliasID, uint8_t serverID, uint8_t functionCode, ModbusClient *client, IPAddress host = IPAddress(0, 0, 0, 0), uint16_t port = 0);
+
+  // Link another function code to the server
+  bool addFunctionCode(uint8_t aliasID, uint8_t functionCode);
+
+  // Block a function code (respond with ILLEGAL_FUNCTION error)
+  bool denyFunctionCode(uint8_t aliasID, uint8_t functionCode);
+
+protected:
+  // ServerData holds all data necessary to address a single server
+  struct ServerData {
+    uint8_t serverID;             // External server id
+    ModbusClient *client;         // client to be used to request the server
+    ServerType serverType;        // TCP_SERVER or RTU_SERVER
+    IPAddress host;               // TCP: host IP address, else 0.0.0.0
+    uint16_t port;                // TCP: host port number, else 0
+
+    // RTU constructor
+    ServerData(uint8_t sid, ModbusClient *c) :
+      serverID(sid),
+      client(c),
+      serverType(RTU_SERVER),
+      host(IPAddress(0, 0, 0, 0)),
+      port(0) {}
+    
+    // TCP constructor
+    ServerData(uint8_t sid, ModbusClient *c, IPAddress h, uint16_t p) :
+      serverID(sid),
+      client(c),
+      serverType(TCP_SERVER),
+      host(h),
+      port(p) {}
+  };
+
+  // Default worker functions
+  ModbusMessage bridgeWorker(ModbusMessage msg);
+  ModbusMessage bridgeDenyWorker(ModbusMessage msg);
+
+  // Map of servers attached
+  std::map<uint8_t, ServerData *> servers;
+};
+
+// Constructor for TCP variants
+template<typename SERVERCLASS>
+ModbusBridge<SERVERCLASS>::ModbusBridge() :
+  SERVERCLASS() { } 
+
+// Constructors for RTU variant
+template<typename SERVERCLASS>
+ModbusBridge<SERVERCLASS>::ModbusBridge(HardwareSerial& serial, uint32_t timeout, int rtsPin) :
+  SERVERCLASS(serial, timeout, rtsPin) { }
+
+// Alternate constructors for RTU variant
+template<typename SERVERCLASS>
+ModbusBridge<SERVERCLASS>::ModbusBridge(HardwareSerial& serial, uint32_t timeout, RTScallback rts) :
+  SERVERCLASS(serial, timeout, rts) { }
+
+// Destructor
+template<typename SERVERCLASS>
+ModbusBridge<SERVERCLASS>::~ModbusBridge() { 
+  // Release ServerData storage in servers array
+  for (auto itr = servers.begin(); itr != servers.end(); itr++) {
+    delete (itr->second);
+  }
+  servers.clear();
+}
+
+// attachServer: memorize the access data for an external server with ID serverID under bridge ID aliasID
+template<typename SERVERCLASS>
+bool ModbusBridge<SERVERCLASS>::attachServer(uint8_t aliasID, uint8_t serverID, uint8_t functionCode, ModbusClient *client, IPAddress host, uint16_t port) {
+
+  // Is there already an entry for the aliasID?
+  if (servers.find(aliasID) == servers.end()) {
+    // No. Store server data in map.
+
+    // Do we have a port number?
+    if (port != 0) {
+      // Yes. Must be a TCP client
+      servers[aliasID] = new ServerData(serverID, static_cast<ModbusClient *>(client), host, port);
+      LOG_D("(TCP): %02X->%02X %d.%d.%d.%d:%d\n", aliasID, serverID, host[0], host[1], host[2], host[3], port);
+    } else {
+      // No - RTU client required
+      servers[aliasID] = new ServerData(serverID, static_cast<ModbusClient *>(client));
+      LOG_D("(RTU): %02X->%02X\n", aliasID, serverID);
+    }
+  }
+
+  // Register the server/FC combination for the bridgeWorker
+  addFunctionCode(aliasID, functionCode);
+  return true;
+}
+
+template<typename SERVERCLASS>
+bool ModbusBridge<SERVERCLASS>::addFunctionCode(uint8_t aliasID, uint8_t functionCode) {
+  // Is there already an entry for the aliasID?
+  if (servers.find(aliasID) != servers.end()) {
+    // Yes. Link server to own worker function
+    this->registerWorker(aliasID, functionCode, std::bind(&ModbusBridge<SERVERCLASS>::bridgeWorker, this, std::placeholders::_1));
+    LOG_D("FC %02X added for server %02X\n", functionCode, aliasID);
+  } else {
+    LOG_E("Server %d not attached to bridge!\n", aliasID);
+    return false;
+  }
+  return true;
+}
+
+template<typename SERVERCLASS>
+bool ModbusBridge<SERVERCLASS>::denyFunctionCode(uint8_t aliasID, uint8_t functionCode) {
+  // Is there already an entry for the aliasID?
+  if (servers.find(aliasID) != servers.end()) {
+    // Yes. Link server to own worker function
+    this->registerWorker(aliasID, functionCode, std::bind(&ModbusBridge<SERVERCLASS>::bridgeDenyWorker, this, std::placeholders::_1));
+    LOG_D("FC %02X blocked for server %02X\n", functionCode, aliasID);
+  } else {
+    LOG_E("Server %d not attached to bridge!\n", aliasID);
+    return false;
+  }
+  return true;
+}
+
+// bridgeWorker: default worker function to process bridge requests
+template<typename SERVERCLASS>
+ModbusMessage ModbusBridge<SERVERCLASS>::bridgeWorker(ModbusMessage msg) {
+  uint8_t aliasID = msg.getServerID();
+  uint8_t functionCode = msg.getFunctionCode();
+  ModbusMessage response;
+
+  // Find the (alias) serverID
+  if (servers.find(aliasID) != servers.end()) {
+    // Found it. We may use servers[aliasID] now without allocating a new map slot
+
+    // Set real target server ID
+    msg.setServerID(servers[aliasID]->serverID);
+
+    // Issue the request
+    LOG_D("Request (%02X/%02X) sent\n", servers[aliasID]->serverID, functionCode);
+    // TCP servers have a target host/port that needs to be set in the client
+    if (servers[aliasID]->serverType == TCP_SERVER) {
+      response = reinterpret_cast<ModbusClientTCP *>(servers[aliasID]->client)->syncRequestMT(msg, (uint32_t)millis(), servers[aliasID]->host, servers[aliasID]->port);
+    } else {
+      response = servers[aliasID]->client->syncRequestM(msg, (uint32_t)millis());
+    }
+
+    // Re-set the requested server ID
+    response.setServerID(aliasID);
+  } else {
+    // If we get here, something has gone wrong internally. We send back an error response anyway.
+    response.setError(aliasID, functionCode, INVALID_SERVER);
+  }
+  return response;
+}
+
+// bridgeDenyWorker: worker function to block function codes
+template<typename SERVERCLASS>
+ModbusMessage ModbusBridge<SERVERCLASS>::bridgeDenyWorker(ModbusMessage msg) {
+  ModbusMessage response;
+  response.setError(msg.getServerID(), msg.getFunctionCode(), ILLEGAL_FUNCTION);
+  return response;
+}
+
+#endif
diff --git a/lib/eModbus/src/ModbusBridgeWiFi.h b/lib/eModbus/src/ModbusBridgeWiFi.h
new file mode 100644
index 000000000..9eb897d55
--- /dev/null
+++ b/lib/eModbus/src/ModbusBridgeWiFi.h
@@ -0,0 +1,18 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_BRIDGE_WIFI_H
+#define _MODBUS_BRIDGE_WIFI_H
+#include "options.h"
+#include <WiFi.h>
+
+#undef SERVER_END
+#define SERVER_END server.end();
+
+#include "ModbusServerTCPtemp.h"
+#include "ModbusBridgeTemp.h"
+
+using ModbusBridgeWiFi = ModbusBridge<ModbusServerTCP<WiFiServer, WiFiClient>>;
+
+#endif
diff --git a/lib/eModbus/src/ModbusClient.cpp b/lib/eModbus/src/ModbusClient.cpp
new file mode 100644
index 000000000..d57c1397a
--- /dev/null
+++ b/lib/eModbus/src/ModbusClient.cpp
@@ -0,0 +1,103 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusClient.h"
+#undef LOCAL_LOG_LEVEL
+#include "Logging.h"
+
+uint16_t ModbusClient::instanceCounter = 0;
+
+// Default constructor: set the default timeout to 2000ms, zero out all other 
+ModbusClient::ModbusClient() :
+  messageCount(0),
+  errorCount(0),
+  #if HAS_FREERTOS
+  worker(NULL),
+  #elif IS_LINUX
+  worker(0),
+  #endif
+  onData(nullptr),
+  onError(nullptr),
+  onResponse(nullptr) { instanceCounter++; }
+
+// onDataHandler: register callback for data responses
+bool ModbusClient::onDataHandler(MBOnData handler) {
+  if (onData) {
+    LOG_W("onData handler was already claimed\n");
+  } else if (onResponse) {
+    LOG_E("onData handler is unavailable with an onResponse handler\n");
+    return false;
+  }
+  onData = handler;
+  return true;
+}
+
+// onErrorHandler: register callback for error responses
+bool ModbusClient::onErrorHandler(MBOnError handler) {
+  if (onError) {
+    LOG_W("onError handler was already claimed\n");
+  } else if (onResponse) {
+    LOG_E("onError handler is unavailable with an onResponse handler\n");
+    return false;
+  } 
+  onError = handler;
+  return true;
+}
+
+// onResponseHandler: register callback for error responses
+bool ModbusClient::onResponseHandler(MBOnResponse handler) {
+  if (onError || onData) {
+    LOG_E("onResponse handler is unavailable with an onData or onError handler\n");
+    return false;
+  } 
+  onResponse = handler;
+  return true;
+}
+
+// getMessageCount: return message counter value
+uint32_t ModbusClient::getMessageCount() {
+  return messageCount;
+}
+
+// getErrorCount: return error counter value
+uint32_t ModbusClient::getErrorCount() {
+  return errorCount;
+}
+
+// resetCounts: Set both message and error counts to zero
+void ModbusClient::resetCounts() {
+  {
+    LOCK_GUARD(cntLock, countAccessM);
+    messageCount = 0;
+    errorCount = 0;
+  }
+}
+
+// waitSync: wait for response on syncRequest to arrive
+ModbusMessage ModbusClient::waitSync(uint8_t serverID, uint8_t functionCode, uint32_t token) {
+  ModbusMessage response;
+  unsigned long lostPatience = millis();
+ 
+  // Default response is TIMEOUT
+  response.setError(serverID, functionCode, TIMEOUT);
+
+  // Loop 60 seconds, if unlucky
+  while (millis() - lostPatience < 60000) {
+    {
+      LOCK_GUARD(lg, syncRespM);
+      // Look for the token
+      auto sR = syncResponse.find(token);
+      // Is it there?
+      if (sR != syncResponse.end()) {
+        // Yes. get the response, delete it from the map and return
+        response = sR->second;
+        syncResponse.erase(sR);
+        break;
+      }
+    }
+    // Give the watchdog time to act
+    delay(10);
+  }
+  return response;
+}
diff --git a/lib/eModbus/src/ModbusClient.h b/lib/eModbus/src/ModbusClient.h
new file mode 100644
index 000000000..2025a1f28
--- /dev/null
+++ b/lib/eModbus/src/ModbusClient.h
@@ -0,0 +1,119 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_CLIENT_H
+#define _MODBUS_CLIENT_H
+
+#include <functional> 
+#include <map>
+#include "options.h"
+#include "ModbusMessage.h"
+
+#if HAS_FREERTOS
+extern "C" {
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+}
+#elif IS_LINUX
+#include <pthread.h>
+#endif
+
+#if USE_MUTEX
+#include <mutex>                    // NOLINT
+using std::mutex;
+using std::lock_guard;
+#endif
+
+typedef std::function<void(ModbusMessage msg, uint32_t token)> MBOnData;
+typedef std::function<void(Modbus::Error errorCode, uint32_t token)> MBOnError;
+typedef std::function<void(ModbusMessage msg, uint32_t token)> MBOnResponse;
+
+class ModbusClient {
+public:
+  bool onDataHandler(MBOnData handler);   // Accept onData handler 
+  bool onErrorHandler(MBOnError handler); // Accept onError handler 
+  bool onResponseHandler(MBOnResponse handler); // Accept onResponse handler 
+  uint32_t getMessageCount();             // Informative: return number of messages created
+  uint32_t getErrorCount();              // Informative: return number of errors received
+  void resetCounts();                    // Set both message and error counts to zero
+  inline Error addRequest(ModbusMessage m, uint32_t token) { return addRequestM(m, token); }
+  inline ModbusMessage syncRequest(ModbusMessage m, uint32_t token) { return syncRequestM(m, token); }
+
+  // Template function to generate syncRequest functions as long as there is a 
+  // matching ModbusMessage::setMessage() call
+  template <typename... Args>
+  ModbusMessage syncRequest(uint32_t token, Args&&... args) {
+    Error rc = SUCCESS;
+    // Create request, if valid
+    ModbusMessage m;
+    rc = m.setMessage(std::forward<Args>(args) ...);
+
+    // Add it to the queue and wait for a response, if valid
+    if (rc == SUCCESS) {
+      return syncRequestM(m, token);
+    } 
+    // Else return the error as a message
+    return buildErrorMsg(rc, std::forward<Args>(args) ...);
+  }
+
+  // Template function to create an error response message from a variadic pattern
+  template <typename... Args>
+  ModbusMessage buildErrorMsg(Error e, uint8_t serverID, uint8_t functionCode, Args&&... args) {
+    ModbusMessage m;
+    m.setError(serverID, functionCode, e);
+    return m;
+  }
+
+  // Template function to generate addRequest functions as long as there is a 
+  // matching ModbusMessage::setMessage() call
+  template <typename... Args>
+  Error addRequest(uint32_t token, Args&&... args) {
+    Error rc = SUCCESS;        // Return value
+
+    // Create request, if valid
+    ModbusMessage m;
+    rc = m.setMessage(std::forward<Args>(args) ...);
+
+    // Add it to the queue, if valid
+    if (rc == SUCCESS) {
+      return addRequestM(m, token);
+    }
+    // Else return the error
+    return rc;
+  }
+
+protected:
+  ModbusClient();             // Default constructor
+  virtual void isInstance() = 0;   // Make class abstract
+  ModbusMessage waitSync(uint8_t serverID, uint8_t functionCode, uint32_t token); // wait for syncRequest response to arrive
+  // Virtual addRequest variant needed internally. All others done by template!
+  virtual Error addRequestM(ModbusMessage msg, uint32_t token) = 0;
+  // Virtual syncRequest variant following the same pattern
+  virtual ModbusMessage syncRequestM(ModbusMessage msg, uint32_t token) = 0;
+  // Prevent copy construction or assignment
+  ModbusClient(ModbusClient& other) = delete;
+  ModbusClient& operator=(ModbusClient& other) = delete;
+
+  uint32_t messageCount;           // Number of requests generated. Used for transactionID in TCPhead
+  uint32_t errorCount;             // Number of errors received
+#if HAS_FREERTOS
+  TaskHandle_t worker;             // Interface instance worker task
+#elif IS_LINUX
+  pthread_t worker;
+#endif
+  MBOnData onData;                 // Data response handler
+  MBOnError onError;               // Error response handler
+  MBOnResponse onResponse;         // Uniform response handler
+  static uint16_t instanceCounter; // Number of ModbusClients created
+  std::map<uint32_t, ModbusMessage> syncResponse; // Map to hold response messages on synchronous requests
+#if USE_MUTEX
+  std::mutex syncRespM;            // Mutex protecting syncResponse map against race conditions
+  std::mutex countAccessM;         // Mutex protecting access to the message and error counts
+#endif
+
+  // Let any ModbusBridge class use protected members
+  template<typename SERVERCLASS> friend class ModbusBridge;
+};
+
+#endif
diff --git a/lib/eModbus/src/ModbusClientRTU.cpp b/lib/eModbus/src/ModbusClientRTU.cpp
new file mode 100644
index 000000000..ecb0fc9b5
--- /dev/null
+++ b/lib/eModbus/src/ModbusClientRTU.cpp
@@ -0,0 +1,349 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusClientRTU.h"
+
+#if HAS_FREERTOS
+
+#undef LOCAL_LOG_LEVEL
+// #define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+#include "Logging.h"
+
+// Constructor takes an optional DE/RE pin and queue size
+ModbusClientRTU::ModbusClientRTU(int8_t rtsPin, uint16_t queueLimit) :
+  ModbusClient(),
+  MR_serial(nullptr),
+  MR_lastMicros(micros()),
+  MR_interval(2000),
+  MR_rtsPin(rtsPin),
+  MR_qLimit(queueLimit),
+  MR_timeoutValue(DEFAULTTIMEOUT),
+  MR_useASCII(false),
+  MR_skipLeadingZeroByte(false) {
+    if (MR_rtsPin >= 0) {
+      pinMode(MR_rtsPin, OUTPUT);
+      MTRSrts = [this](bool level) {
+        digitalWrite(MR_rtsPin, level);
+      };
+      MTRSrts(LOW);
+    } else {
+      MTRSrts = RTUutils::RTSauto;
+    }
+}
+
+// Alternative constructor takes an RTS callback function
+ModbusClientRTU::ModbusClientRTU(RTScallback rts, uint16_t queueLimit) :
+  ModbusClient(),
+  MR_serial(nullptr),
+  MR_lastMicros(micros()),
+  MR_interval(2000),
+  MTRSrts(rts),
+  MR_qLimit(queueLimit),
+  MR_timeoutValue(DEFAULTTIMEOUT),
+  MR_useASCII(false),
+  MR_skipLeadingZeroByte(false) {
+    MR_rtsPin = -1;
+    MTRSrts(LOW);
+}
+
+// Destructor: clean up queue, task etc.
+ModbusClientRTU::~ModbusClientRTU() {
+  // Kill worker task and clean up request queue
+  end();
+}
+
+// begin: start worker task - general version
+void ModbusClientRTU::begin(Stream& serial, uint32_t baudRate, int coreID) {
+  MR_serial = &serial;
+  doBegin(baudRate, coreID);
+}
+
+// begin: start worker task - HardwareSerial version
+void ModbusClientRTU::begin(HardwareSerial& serial, int coreID) {
+  MR_serial = &serial;
+  uint32_t baudRate = serial.baudRate();
+  serial.setRxFIFOFull(1);
+  doBegin(baudRate, coreID);
+}
+
+void ModbusClientRTU::doBegin(uint32_t baudRate, int coreID) {
+  // Task already running? End it in case
+  end();
+
+  // Pull down RTS toggle, if necessary
+  MTRSrts(LOW);
+
+  // Set minimum interval time
+  MR_interval = RTUutils::calculateInterval(baudRate);
+
+  // Create unique task name
+  char taskName[18];
+  snprintf(taskName, 18, "Modbus%02XRTU", instanceCounter);
+  // Start task to handle the queue
+  xTaskCreatePinnedToCore((TaskFunction_t)&handleConnection, taskName, CLIENT_TASK_STACK, this, 6, &worker, coreID >= 0 ? coreID : NULL);
+
+  LOG_D("Client task %d started. Interval=%d\n", (uint32_t)worker, MR_interval);
+}
+
+// end: stop worker task
+void ModbusClientRTU::end() {
+  if (worker) {
+    // Clean up queue
+    {
+      // Safely lock access
+      LOCK_GUARD(lockGuard, qLock);
+      // Get all queue entries one by one
+      while (!requests.empty()) {
+        // Remove front entry
+        requests.pop();
+      }
+    }
+    // Kill task
+    vTaskDelete(worker);
+    LOG_D("Client task %d killed.\n", (uint32_t)worker);
+    worker = nullptr;
+  }
+}
+
+// setTimeOut: set/change the default interface timeout
+void ModbusClientRTU::setTimeout(uint32_t TOV) {
+  MR_timeoutValue = TOV;
+  LOG_D("Timeout set to %d\n", TOV);
+}
+
+// Toggle protocol to ModbusASCII
+void ModbusClientRTU::useModbusASCII(unsigned long timeout) {
+  MR_useASCII = true;
+  MR_timeoutValue = timeout; // Switch timeout to ASCII's value
+  LOG_D("Protocol mode: ASCII\n");
+}
+
+// Toggle protocol to ModbusRTU
+void ModbusClientRTU::useModbusRTU() {
+  MR_useASCII = false;
+  LOG_D("Protocol mode: RTU\n");
+}
+
+// Inquire protocol mode
+bool ModbusClientRTU::isModbusASCII() {
+  return MR_useASCII;
+}
+
+// Toggle skipping of leading 0x00 byte
+void ModbusClientRTU::skipLeading0x00(bool onOff) {
+  MR_skipLeadingZeroByte = onOff;
+  LOG_D("Skip leading 0x00 mode = %s\n", onOff ? "ON" : "OFF");
+}
+
+// Return number of unprocessed requests in queue
+uint32_t ModbusClientRTU::pendingRequests() {
+  return requests.size();
+}
+
+// Remove all pending request from queue
+void ModbusClientRTU::clearQueue()
+{
+  std::queue<RequestEntry> empty;
+  LOCK_GUARD(lockGuard, qLock);
+  std::swap(requests, empty);
+}
+
+// Base addRequest taking a preformatted data buffer and length as parameters
+Error ModbusClientRTU::addRequestM(ModbusMessage msg, uint32_t token) {
+  Error rc = SUCCESS;        // Return value
+
+  LOG_D("request for %02X/%02X\n", msg.getServerID(), msg.getFunctionCode());
+
+  // Add it to the queue, if valid
+  if (msg) {
+    // Queue add successful?
+    if (!addToQueue(token, msg)) {
+      // No. Return error after deleting the allocated request.
+      rc = REQUEST_QUEUE_FULL;
+    }
+  }
+
+  LOG_D("RC=%02X\n", rc);
+  return rc;
+}
+
+// Base syncRequest follows the same pattern
+ModbusMessage ModbusClientRTU::syncRequestM(ModbusMessage msg, uint32_t token) {
+  ModbusMessage response;
+
+  if (msg) {
+    // Queue add successful?
+    if (!addToQueue(token, msg, true)) {
+      // No. Return error after deleting the allocated request.
+      response.setError(msg.getServerID(), msg.getFunctionCode(), REQUEST_QUEUE_FULL);
+    } else {
+      // Request is queued - wait for the result.
+      response = waitSync(msg.getServerID(), msg.getFunctionCode(), token);
+    }
+  } else {
+    response.setError(msg.getServerID(), msg.getFunctionCode(), EMPTY_MESSAGE);
+  }
+  return response;
+}
+
+// addBroadcastMessage: create a fire-and-forget message to all servers on the RTU bus
+Error ModbusClientRTU::addBroadcastMessage(const uint8_t *data, uint8_t len) {
+  Error rc = SUCCESS;        // Return value
+
+  LOG_D("Broadcast request of length %d\n", len);
+
+  // We do only accept requests with data, 0 byte, data and CRC must fit into 256 bytes.
+  if (len && len < 254) {
+    // Create a "broadcast token"
+    uint32_t token = (millis() & 0xFFFFFF) | 0xBC000000;
+    ModbusMessage msg;
+    
+    // Server ID is 0x00 for broadcast
+    msg.add((uint8_t)0x00);
+    // Append data
+    msg.add(data, len);
+
+    // Queue add successful?
+    if (!addToQueue(token, msg)) {
+      // No. Return error after deleting the allocated request.
+      rc = REQUEST_QUEUE_FULL;
+    }
+  } else {
+    rc =  BROADCAST_ERROR;
+  }
+
+  LOG_D("RC=%02X\n", rc);
+  return rc;
+}
+
+
+// addToQueue: send freshly created request to queue
+bool ModbusClientRTU::addToQueue(uint32_t token, ModbusMessage request, bool syncReq) {
+  bool rc = false;
+  // Did we get one?
+  if (request) {
+    RequestEntry re(token, request, syncReq);
+    if (requests.size()<MR_qLimit) {
+      // Yes. Safely lock queue and push request to queue
+      rc = true;
+      LOCK_GUARD(lockGuard, qLock);
+      requests.push(re);
+    }
+    {
+      LOCK_GUARD(cntLock, countAccessM);
+      messageCount++;
+    }
+  }
+
+  LOG_D("RC=%02X\n", rc);
+  return rc;
+}
+
+// handleConnection: worker task
+// This was created in begin() to handle the queue entries
+void ModbusClientRTU::handleConnection(ModbusClientRTU *instance) {
+  // initially clean the serial buffer
+  while (instance->MR_serial->available()) instance->MR_serial->read();
+  delay(100);
+
+  // Loop forever - or until task is killed
+  while (1) {
+    // Do we have a reuest in queue?
+    if (!instance->requests.empty()) {
+      // Yes. pull it.
+      RequestEntry request = instance->requests.front();
+
+      LOG_D("Pulled request from queue\n");
+
+      // Send it via Serial
+      RTUutils::send(*(instance->MR_serial), instance->MR_lastMicros, instance->MR_interval, instance->MTRSrts, request.msg, instance->MR_useASCII);
+
+      LOG_D("Request sent.\n");
+      // HEXDUMP_V("Data", request.msg.data(), request.msg.size());
+
+      // For a broadcast, we will not wait for a response
+      if (request.msg.getServerID() != 0 || ((request.token & 0xFF000000) != 0xBC000000)) {
+        // This is a regular request, Get the response - if any
+        ModbusMessage response = RTUutils::receive(
+          'C',
+          *(instance->MR_serial), 
+          instance->MR_timeoutValue, 
+          instance->MR_lastMicros, 
+          instance->MR_interval, 
+          instance->MR_useASCII,
+          instance->MR_skipLeadingZeroByte);
+  
+        LOG_D("%s response (%d bytes) received.\n", response.size()>1 ? "Data" : "Error", response.size());
+        HEXDUMP_V("Data", response.data(), response.size());
+  
+        // No error in receive()?
+        if (response.size() > 1) {
+          // No. Check message contents
+          // Does the serverID match the requested?
+          if (request.msg.getServerID() != response.getServerID()) {
+            // No. Return error response
+            response.setError(request.msg.getServerID(), request.msg.getFunctionCode(), SERVER_ID_MISMATCH);
+          // ServerID ok, but does the FC match as well?
+          } else if (request.msg.getFunctionCode() != (response.getFunctionCode() & 0x7F)) {
+            // No. Return error response
+            response.setError(request.msg.getServerID(), request.msg.getFunctionCode(), FC_MISMATCH);
+          } 
+        } else {
+          // No, we got an error code from receive()
+          // Return it as error response
+          response.setError(request.msg.getServerID(), request.msg.getFunctionCode(), static_cast<Error>(response[0]));
+        }
+  
+        LOG_D("Response generated.\n");
+        HEXDUMP_V("Response packet", response.data(), response.size());
+
+        // If we got an error, count it
+        if (response.getError() != SUCCESS) {
+          instance->errorCount++;
+        }
+  
+        // Was it a synchronous request?
+        if (request.isSyncRequest) {
+          // Yes. Put it into the response map
+          {
+            LOCK_GUARD(sL, instance->syncRespM);
+            instance->syncResponse[request.token] = response;
+          }
+        // No, an async request. Do we have an onResponse handler?
+        } else if (instance->onResponse) {
+          // Yes. Call it
+          instance->onResponse(response, request.token);
+        } else {
+          // No, but we may have onData or onError handlers
+          // Did we get a normal response?
+          if (response.getError()==SUCCESS) {
+            // Yes. Do we have an onData handler registered?
+            if (instance->onData) {
+              // Yes. call it
+              instance->onData(response, request.token);
+            }
+          } else {
+            // No, something went wrong. All we have is an error
+            // Do we have an onError handler?
+            if (instance->onError) {
+              // Yes. Forward the error code to it
+              instance->onError(response.getError(), request.token);
+            }
+          }
+        }
+      }
+      // Clean-up time. 
+      {
+        // Safely lock the queue
+        LOCK_GUARD(lockGuard, instance->qLock);
+        // Remove the front queue entry
+        instance->requests.pop();
+      }
+    } else {
+      delay(1);
+    }
+  }
+}
+
+#endif  // HAS_FREERTOS
diff --git a/lib/eModbus/src/ModbusClientRTU.h b/lib/eModbus/src/ModbusClientRTU.h
new file mode 100644
index 000000000..fb4fedbf5
--- /dev/null
+++ b/lib/eModbus/src/ModbusClientRTU.h
@@ -0,0 +1,111 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_CLIENT_RTU_H
+#define _MODBUS_CLIENT_RTU_H
+
+#include "options.h"
+
+#if HAS_FREERTOS
+
+#include "ModbusClient.h"
+#include "Stream.h"
+#include "RTUutils.h"
+#include <queue>
+#include <vector>
+
+using std::queue;
+
+#define DEFAULTTIMEOUT 2000
+
+class ModbusClientRTU : public ModbusClient {
+public:
+  // Constructor takes an optional DE/RE pin and queue limit
+  explicit ModbusClientRTU(int8_t rtsPin = -1, uint16_t queueLimit = 100);
+
+  // Alternative Constructor takes an RTS line toggle callback
+  explicit ModbusClientRTU(RTScallback rts, uint16_t queueLimit = 100);
+
+  // Destructor: clean up queue, task etc.
+  ~ModbusClientRTU();
+
+  // begin: start worker task
+  void begin(Stream& serial, uint32_t baudrate, int coreID = -1);
+  // Special variant for HardwareSerial
+  void begin(HardwareSerial& serial, int coreID = -1);
+
+  // end: stop the worker
+  void end();
+
+  // Set default timeout value for interface
+  void setTimeout(uint32_t TOV);
+
+  // Toggle protocol to ModbusASCII
+  void useModbusASCII(unsigned long timeout = 1000);
+
+  // Toggle protocol to ModbusRTU
+  void useModbusRTU();
+
+  // Inquire protocol mode
+  bool isModbusASCII();
+
+  // Toggle skipping of leading 0x00 byte
+  void skipLeading0x00(bool onOff = true);
+
+  // Return number of unprocessed requests in queue
+  uint32_t pendingRequests();
+
+  // Remove all pending request from queue
+  void clearQueue();
+  
+  // addBroadcastMessage: create a fire-and-forget message to all servers on the RTU bus
+  Error addBroadcastMessage(const uint8_t *data, uint8_t len);
+
+protected:
+  struct RequestEntry {
+    uint32_t token;
+    ModbusMessage msg;
+    bool isSyncRequest;
+    RequestEntry(uint32_t t, ModbusMessage m, bool syncReq = false) :
+      token(t),
+      msg(m),
+      isSyncRequest(syncReq) {}
+  };
+
+  // Base addRequest and syncRequest must be present
+  Error addRequestM(ModbusMessage msg, uint32_t token);
+  ModbusMessage syncRequestM(ModbusMessage msg, uint32_t token);
+
+  // addToQueue: send freshly created request to queue
+  bool addToQueue(uint32_t token, ModbusMessage msg, bool syncReq = false);
+
+  // handleConnection: worker task method
+  static void handleConnection(ModbusClientRTU *instance);
+
+  // receive: get response via Serial
+  ModbusMessage receive(const ModbusMessage request);
+
+  // start background task
+  void doBegin(uint32_t baudRate, int coreID);
+
+  void isInstance() { return; }   // make class instantiable
+  queue<RequestEntry> requests;   // Queue to hold requests to be processed
+  #if USE_MUTEX
+  mutex qLock;                    // Mutex to protect queue
+  #endif
+  Stream *MR_serial;              // Ptr to the serial interface used
+  unsigned long MR_lastMicros;    // Microseconds since last bus activity
+  uint32_t MR_interval;           // Modbus RTU bus quiet time
+  int8_t MR_rtsPin;               // GPIO pin to toggle RS485 DE/RE line. -1 if none.
+  RTScallback MTRSrts;            // RTS line callback function
+  uint16_t MR_qLimit;             // Maximum number of requests to hold in the queue
+  uint32_t MR_timeoutValue;       // Interface default timeout
+  bool MR_useASCII;               // true=ModbusASCII, false=ModbusRTU
+  bool MR_skipLeadingZeroByte;    // true=skip the first byte if it is 0x00, false=accept all bytes
+
+};
+
+#endif  // HAS_FREERTOS
+
+#endif  // INCLUDE GUARD
diff --git a/lib/eModbus/src/ModbusClientTCP.cpp b/lib/eModbus/src/ModbusClientTCP.cpp
new file mode 100644
index 000000000..ec34a2d52
--- /dev/null
+++ b/lib/eModbus/src/ModbusClientTCP.cpp
@@ -0,0 +1,428 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusClientTCP.h"
+
+#if HAS_FREERTOS || IS_LINUX
+
+#undef LOCAL_LOG_LEVEL
+// #define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+#include "Logging.h"
+
+// Constructor takes reference to Client (EthernetClient or WiFiClient)
+ModbusClientTCP::ModbusClientTCP(Client& client, uint16_t queueLimit) :
+  ModbusClient(),
+  MT_client(client),
+  MT_lastTarget(IPAddress(0, 0, 0, 0), 0, DEFAULTTIMEOUT, TARGETHOSTINTERVAL),
+  MT_target(IPAddress(0, 0, 0, 0), 0, DEFAULTTIMEOUT, TARGETHOSTINTERVAL),
+  MT_defaultTimeout(DEFAULTTIMEOUT),
+  MT_defaultInterval(TARGETHOSTINTERVAL),
+  MT_qLimit(queueLimit)
+  { }
+
+// Alternative Constructor takes reference to Client (EthernetClient or WiFiClient) plus initial target host
+ModbusClientTCP::ModbusClientTCP(Client& client, IPAddress host, uint16_t port, uint16_t queueLimit) :
+  ModbusClient(),
+  MT_client(client),
+  MT_lastTarget(IPAddress(0, 0, 0, 0), 0, DEFAULTTIMEOUT, TARGETHOSTINTERVAL),
+  MT_target(host, port, DEFAULTTIMEOUT, TARGETHOSTINTERVAL),
+  MT_defaultTimeout(DEFAULTTIMEOUT),
+  MT_defaultInterval(TARGETHOSTINTERVAL),
+  MT_qLimit(queueLimit)
+  { }
+
+// Destructor: clean up queue, task etc.
+ModbusClientTCP::~ModbusClientTCP() {
+  end();
+}
+
+// end: stop worker task
+void ModbusClientTCP::end() {
+  // Clean up queue
+  {
+    // Safely lock access
+    LOCK_GUARD(lockGuard, qLock);
+    // Get all queue entries one by one
+    while (!requests.empty()) {
+      requests.pop();
+    }
+  }
+  LOG_D("TCP client worker killed.\n");
+  // Kill task
+  if (worker) {
+#if IS_LINUX
+    pthread_cancel(worker);
+    worker = NULL;
+#else
+    vTaskDelete(worker);
+    worker = nullptr;
+#endif
+  }
+}
+
+// begin: start worker task
+#if IS_LINUX
+void *ModbusClientTCP::pHandle(void *p) {
+  handleConnection((ModbusClientTCP *)p);
+  return nullptr;
+}
+#endif
+
+void ModbusClientTCP::begin(int coreID) {
+  if (!worker) {
+#if IS_LINUX
+    int rc = pthread_create(&worker, NULL, &pHandle, this);
+    if (rc) {
+      LOG_E("Error creating TCP client thread: %d\n", rc);
+    } else {
+      LOG_D("TCP client worker started.\n");
+    }
+
+#else
+    // Create unique task name
+    char taskName[18];
+    snprintf(taskName, 18, "Modbus%02XTCP", instanceCounter);
+    // Start task to handle the queue
+    xTaskCreatePinnedToCore((TaskFunction_t)&handleConnection, taskName, CLIENT_TASK_STACK, this, 5, &worker, coreID >= 0 ? coreID : NULL);
+    LOG_D("TCP client worker %s started\n", taskName);
+#endif
+  } else {
+    LOG_E("Worker thread has been already started!");
+  }
+}
+
+// Set default timeout value (and interval)
+void ModbusClientTCP::setTimeout(uint32_t timeout, uint32_t interval) {
+  MT_defaultTimeout = timeout;
+  MT_defaultInterval = interval;
+}
+
+// Switch target host (if necessary)
+// Return true, if host/port is different from last host/port used
+bool ModbusClientTCP::setTarget(IPAddress host, uint16_t port, uint32_t timeout, uint32_t interval) {
+  MT_target.host = host;
+  MT_target.port = port;
+  MT_target.timeout = timeout ? timeout : MT_defaultTimeout;
+  MT_target.interval = interval ? interval : MT_defaultInterval;
+  LOG_D("Target set: %d.%d.%d.%d:%d\n", host[0], host[1], host[2], host[3], port);
+  if (MT_target.host == MT_lastTarget.host && MT_target.port == MT_lastTarget.port) return false;
+  return true;
+}
+
+// Return number of unprocessed requests in queue
+uint32_t ModbusClientTCP::pendingRequests() {
+  return requests.size();
+}
+
+// Remove all pending request from queue
+void ModbusClientTCP::clearQueue() {
+  std::queue<RequestEntry *> empty;
+  LOCK_GUARD(lockGuard, qLock);
+  std::swap(requests, empty);
+}
+
+// Base addRequest for preformatted ModbusMessage and last set target
+Error ModbusClientTCP::addRequestM(ModbusMessage msg, uint32_t token) {
+  Error rc = SUCCESS;        // Return value
+
+  // Add it to the queue, if valid
+  if (msg) {
+    // Queue add successful?
+    if (!addToQueue(token, msg, MT_target)) {
+      // No. Return error after deleting the allocated request.
+      rc = REQUEST_QUEUE_FULL;
+    }
+  }
+
+  LOG_D("Add TCP request result: %02X\n", rc);
+  return rc;
+}
+
+// TCP addRequest for preformatted ModbusMessage and adhoc target
+Error ModbusClientTCP::addRequestMT(ModbusMessage msg, uint32_t token, IPAddress targetHost, uint16_t targetPort) {
+  Error rc = SUCCESS;        // Return value
+
+  // Add it to the queue, if valid
+  if (msg) {
+    // Set up adhoc target 
+    TargetHost adhocTarget(targetHost, targetPort, MT_defaultTimeout, MT_defaultInterval);
+    // Queue add successful?
+    if (!addToQueue(token, msg, adhocTarget, true)) {
+      // No. Return error after deleting the allocated request.
+      rc = REQUEST_QUEUE_FULL;
+    }
+  }
+
+  LOG_D("Add TCP request result: %02X\n", rc);
+  return rc;
+}
+
+// Base syncRequest follows the same pattern
+ModbusMessage ModbusClientTCP::syncRequestM(ModbusMessage msg, uint32_t token) {
+  ModbusMessage response;
+
+  if (msg) {
+    // Queue add successful?
+    if (!addToQueue(token, msg, MT_target, true)) {
+      // No. Return error after deleting the allocated request.
+      response.setError(msg.getServerID(), msg.getFunctionCode(), REQUEST_QUEUE_FULL);
+    } else {
+      // Request is queued - wait for the result.
+      response = waitSync(msg.getServerID(), msg.getFunctionCode(), token);
+    }
+  } else {
+    response.setError(msg.getServerID(), msg.getFunctionCode(), EMPTY_MESSAGE);
+  }
+  return response;
+}
+
+// TCP syncRequest with adhoc target parameters
+ModbusMessage ModbusClientTCP::syncRequestMT(ModbusMessage msg, uint32_t token, IPAddress targetHost, uint16_t targetPort) {
+  ModbusMessage response;
+
+  if (msg) {
+    // Set up adhoc target 
+    TargetHost adhocTarget(targetHost, targetPort, MT_defaultTimeout, MT_defaultInterval);
+    // Queue add successful?
+    if (!addToQueue(token, msg, adhocTarget, true)) {
+      // No. Return error after deleting the allocated request.
+      response.setError(msg.getServerID(), msg.getFunctionCode(), REQUEST_QUEUE_FULL);
+    } else {
+      // Request is queued - wait for the result.
+      response = waitSync(msg.getServerID(), msg.getFunctionCode(), token);
+    }
+  } else {
+    response.setError(msg.getServerID(), msg.getFunctionCode(), EMPTY_MESSAGE);
+  }
+  return response;
+}
+
+// addToQueue: send freshly created request to queue
+bool ModbusClientTCP::addToQueue(uint32_t token, ModbusMessage request, TargetHost target, bool syncReq) {
+  bool rc = false;
+  // Did we get one?
+  LOG_D("Queue size: %d\n", (uint32_t)requests.size());
+  HEXDUMP_D("Enqueue", request.data(), request.size());
+  if (request) {
+    if (requests.size()<MT_qLimit) {
+      RequestEntry *re = new RequestEntry(token, request, target, syncReq);
+      // inject proper transactionID
+      re->head.transactionID = messageCount++;
+      re->head.len = request.size();
+      // Safely lock queue and push request to queue
+      rc = true;
+      LOCK_GUARD(lockGuard, qLock);
+      requests.push(re);
+    }
+  }
+
+  return rc;
+}
+
+// handleConnection: worker task
+// This was created in begin() to handle the queue entries
+void ModbusClientTCP::handleConnection(ModbusClientTCP *instance) {
+  bool doNotPop;
+  unsigned long lastRequest = millis();
+
+  // Loop forever - or until task is killed
+  while (1) {
+    // Do we have a request in queue?
+    if (!instance->requests.empty()) {
+      // Yes. pull it.
+      RequestEntry *request = instance->requests.front();
+      doNotPop = false;
+      LOG_D("Got request from queue\n");
+
+      // Do we have a connection open?
+      if (instance->MT_client.connected()) {
+        // Empty the RX buffer in case there is a stray response left
+        while (instance->MT_client.read() != -1) {}
+        // check if lastHost/lastPort!=host/port off the queued request
+        if (instance->MT_lastTarget != request->target) {
+          // It is different. Disconnect it.
+          instance->MT_client.stop();
+          LOG_D("Target different, disconnect\n");
+          delay(1);  // Give scheduler room to breathe
+        } else {
+          // it is the same host/port.
+          // Give it some slack to get ready again
+          while (millis() - lastRequest < request->target.interval) { delay(1); }
+        }
+      }
+      // if client is disconnected (we will have to switch hosts)
+      if (!instance->MT_client.connected()) {
+        // Serial.println("Client reconnecting");
+        // It is disconnected. connect to host/port from queue
+        instance->MT_client.connect(request->target.host, request->target.port);
+        LOG_D("Target connect (%d.%d.%d.%d:%d).\n", request->target.host[0], request->target.host[1], request->target.host[2], request->target.host[3], request->target.port);
+
+        delay(1);  // Give scheduler room to breathe
+      }
+      ModbusMessage response;
+      // Are we connected (again)?
+      if (instance->MT_client.connected()) {
+        LOG_D("Is connected. Send request.\n");
+        // Yes. Send the request via IP
+        instance->send(request);
+
+        // Get the response - if any
+        response = instance->receive(request);
+
+        // Did we get a normal response?
+        if (response.getError()==SUCCESS) {
+          LOG_D("Data response.\n");
+          // Yes. Is it a synchronous request?
+          if (request->isSyncRequest) {
+            // Yes. Put the response into the response map
+            {
+              LOCK_GUARD(sL, instance->syncRespM);
+              instance->syncResponse[request->token] = response;
+            }
+          // No, async request. Do we have an onResponse handler?
+          } else if (instance->onResponse) {
+            // Yes. Call it.
+            instance->onResponse(response, request->token);
+          // No, but do we have an onData handler registered?
+          } else if (instance->onData) {
+            // Yes. call it
+            instance->onData(response, request->token);
+          } else {
+            LOG_D("No handler for response!\n");
+          }
+        } else {
+          // No, something went wrong. All we have is an error
+          LOG_D("Error response.\n");
+          // Count it
+          {
+            LOCK_GUARD(responseCnt, instance->countAccessM);
+            instance->errorCount++;
+          }
+          // Is it a synchronous request?
+          if (request->isSyncRequest) {
+            // Yes. Put the response into the response map
+            {
+              LOCK_GUARD(sL, instance->syncRespM);
+              instance->syncResponse[request->token] = response;
+            }
+          // No, but do we have an onResponse handler?
+          } else if (instance->onResponse) {
+            // Yes, call it.
+            instance->onResponse(response, request->token);
+          // No, but do we have an onError handler?
+          } else if (instance->onError) {
+            // Yes. Forward the error code to it
+            instance->onError(response.getError(), request->token);
+          } else {
+            LOG_D("No onError handler\n");
+          }
+        }
+        //   set lastHost/lastPort tp host/port
+        instance->MT_lastTarget = request->target;
+      } else {
+        // Oops. Connection failed
+        response.setError(request->msg.getServerID(), request->msg.getFunctionCode(), IP_CONNECTION_FAILED);
+        // Is it a synchronous request?
+        if (request->isSyncRequest) {
+          // Yes. Put the response into the response map
+          {
+            LOCK_GUARD(sL, instance->syncRespM);
+            instance->syncResponse[request->token] = response;
+          }
+        // No, but do we have an onResponse handler?
+        } else if (instance->onResponse) {
+          // Yes, call it.
+          instance->onResponse(response, request->token);
+        // Finally, do we have an onError handler?
+        } else if (instance->onError) {
+          // Yes. Forward the error code to it
+          instance->onError(IP_CONNECTION_FAILED, request->token);
+        }
+      }
+      // Clean-up time. 
+      if (!doNotPop)
+      {
+        // Safely lock the queue
+        LOCK_GUARD(lockGuard, instance->qLock);
+        // Remove the front queue entry
+        instance->requests.pop();
+        // Delete request
+        delete request;
+        LOG_D("Request popped from queue.\n");
+      }
+      lastRequest = millis();
+    } else {
+      delay(1);  // Give scheduler room to breathe
+    }
+  }
+}
+
+// send: send request via Client connection
+void ModbusClientTCP::send(RequestEntry *request) {
+  // We have a established connection here, so we can write right away.
+  // Move tcpHead and request into one continuous buffer, since the very first request tends to 
+  // take too long to be sent to be recognized.
+  ModbusMessage m;
+  m.add((const uint8_t *)request->head, 6);
+  m.append(request->msg);
+
+  MT_client.write(m.data(), m.size());
+  // Done. Are we?
+  MT_client.flush();
+  HEXDUMP_V("Request packet", m.data(), m.size());
+}
+
+// receive: get response via Client connection
+ModbusMessage ModbusClientTCP::receive(RequestEntry *request) {
+  unsigned long lastMillis = millis();     // Timer to check for timeout
+  bool hadData = false;               // flag data received
+  const uint16_t dataLen(300);        // Modbus Packet supposedly will fit (260<300)
+  uint8_t data[dataLen];              // Local buffer to collect received data
+  uint16_t dataPtr = 0;               // Pointer into data
+  ModbusMessage response;             // Response structure to be returned
+
+  // wait for packet data, overflow or timeout
+  while (millis() - lastMillis < request->target.timeout && dataPtr < dataLen && !hadData) {
+    // Is there data waiting?
+    if (MT_client.available()) {
+      // Yes. catch as much as is there and fits into buffer
+      while (MT_client.available() && dataPtr < dataLen) {
+        data[dataPtr++] = MT_client.read();
+      }
+      // Register data received
+      hadData = true;
+      // Rewind EOT and timeout timers
+      lastMillis = millis();
+    }
+    delay(1); // Give scheduler room to breathe
+  }
+  // Did we get some data?
+  if (hadData) {
+    LOG_D("Received response.\n");
+    HEXDUMP_V("Response packet", data, dataPtr);
+    // Yes. check it for validity
+    // First transactionID and protocolID shall be identical, length has to match the remainder.
+    ModbusTCPhead head(request->head.transactionID, request->head.protocolID, dataPtr - 6);
+    // Matching head?
+    if (memcmp((const uint8_t *)head, data, 6)) {
+      // No. return Error response
+      response.setError(request->msg.getServerID(), request->msg.getFunctionCode(), TCP_HEAD_MISMATCH);
+      // If the server id does not match that of the request, report error
+    } else if (data[6] != request->msg.getServerID()) {
+      response.setError(request->msg.getServerID(), request->msg.getFunctionCode(), SERVER_ID_MISMATCH);
+      // If the function code does not match that of the request, report error
+    } else if ((data[7] & 0x7F) != request->msg.getFunctionCode()) {
+      response.setError(request->msg.getServerID(), request->msg.getFunctionCode(), FC_MISMATCH);
+    } else {
+      // Looks good.
+      response.add(data + 6, dataPtr - 6);
+    }
+  } else {
+    // No, timeout must have struck
+    response.setError(request->msg.getServerID(), request->msg.getFunctionCode(), TIMEOUT);
+  }
+  return response;
+}
+
+#endif
diff --git a/lib/eModbus/src/ModbusClientTCP.h b/lib/eModbus/src/ModbusClientTCP.h
new file mode 100644
index 000000000..23f4af5c2
--- /dev/null
+++ b/lib/eModbus/src/ModbusClientTCP.h
@@ -0,0 +1,195 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_CLIENT_TCP_H
+#define _MODBUS_CLIENT_TCP_H
+
+#include "options.h"
+
+#if HAS_FREERTOS || IS_LINUX
+#if HAS_FREERTOS
+#include <Arduino.h>
+#endif
+
+#include "ModbusClient.h"
+#include "Client.h"
+#include <queue>
+#include <vector>
+using std::queue;
+
+#define TARGETHOSTINTERVAL 10
+#define DEFAULTTIMEOUT 2000
+
+class ModbusClientTCP : public ModbusClient {
+public:
+  // Constructor takes reference to Client (EthernetClient or WiFiClient)
+  explicit ModbusClientTCP(Client& client, uint16_t queueLimit = 100);
+
+  // Alternative Constructor takes reference to Client (EthernetClient or WiFiClient) plus initial target host
+  ModbusClientTCP(Client& client, IPAddress host, uint16_t port, uint16_t queueLimit = 100);
+
+  // Destructor: clean up queue, task etc.
+  ~ModbusClientTCP();
+
+  // begin: start worker task
+  void begin(int coreID = -1);
+
+  // end: stop worker task
+  void end();
+
+  // Set default timeout value (and interval)
+  void setTimeout(uint32_t timeout = DEFAULTTIMEOUT, uint32_t interval = TARGETHOSTINTERVAL);
+
+  // Switch target host (if necessary)
+  bool setTarget(IPAddress host, uint16_t port, uint32_t timeout = 0, uint32_t interval = 0);
+
+  // Return number of unprocessed requests in queue
+  uint32_t pendingRequests();
+
+  // Remove all pending request from queue
+  void clearQueue();
+
+protected:
+  // class describing a target server
+  struct TargetHost {
+    IPAddress     host;         // IP address
+    uint16_t      port;         // Port number
+    uint32_t      timeout;      // Time in ms waiting for a response
+    uint32_t      interval;     // Time in ms to wait between requests
+    
+    inline TargetHost& operator=(TargetHost& t) {
+      host = t.host;
+      port = t.port;
+      timeout = t.timeout;
+      interval = t.interval;
+      return *this;
+    }
+    
+    inline TargetHost(TargetHost& t) :
+      host(t.host),
+      port(t.port),
+      timeout(t.timeout),
+      interval(t.interval) {}
+    
+    inline TargetHost() :
+      host(IPAddress(0, 0, 0, 0)),
+      port(0),
+      timeout(0),
+      interval(0)
+    { }
+
+    inline TargetHost(IPAddress host, uint16_t port, uint32_t timeout, uint32_t interval) :
+      host(host),
+      port(port),
+      timeout(timeout),
+      interval(interval)
+    { }
+
+    inline bool operator==(TargetHost& t) {
+      if (host != t.host) return false;
+      if (port != t.port) return false;
+      return true;
+    }
+
+    inline bool operator!=(TargetHost& t) {
+      if (host != t.host) return true;
+      if (port != t.port) return true;
+      return false;
+    }
+  };
+
+  // class describing the TCP header of Modbus packets
+  class ModbusTCPhead {
+  public:
+    ModbusTCPhead() :
+    transactionID(0),
+    protocolID(0),
+    len(0) {}
+
+    ModbusTCPhead(uint16_t tid, uint16_t pid, uint16_t _len) :
+    transactionID(tid),
+    protocolID(pid),
+    len(_len) {}
+
+    uint16_t transactionID;     // Caller-defined identification
+    uint16_t protocolID;        // const 0x0000
+    uint16_t len;               // Length of remainder of TCP packet
+
+    inline explicit operator const uint8_t *() {
+      uint8_t *cp = headRoom;
+      *cp++ = (transactionID >> 8) & 0xFF;
+      *cp++ = transactionID  & 0xFF;
+      *cp++ = (protocolID >> 8) & 0xFF;
+      *cp++ = protocolID  & 0xFF;
+      *cp++ = (len >> 8) & 0xFF;
+      *cp++ = len  & 0xFF;
+      return headRoom;
+    }
+
+    inline ModbusTCPhead& operator= (ModbusTCPhead& t) {
+      transactionID = t.transactionID;
+      protocolID    = t.protocolID;
+      len           = t.len;
+      return *this;
+    }
+
+  protected:
+    uint8_t headRoom[6];        // Buffer to hold MSB-first TCP header
+  };
+
+  struct RequestEntry {
+    uint32_t token;
+    ModbusMessage msg;
+    TargetHost target;
+    ModbusTCPhead head;
+    bool isSyncRequest;
+    RequestEntry(uint32_t t, ModbusMessage m, TargetHost tg, bool syncReq = false) :
+      token(t),
+      msg(m),
+      target(tg),
+      head(ModbusTCPhead()),
+      isSyncRequest(syncReq) {}
+  };
+
+  // Base addRequest and syncRequest must be present
+  Error addRequestM(ModbusMessage msg, uint32_t token);
+  ModbusMessage syncRequestM(ModbusMessage msg, uint32_t token);
+  // TCP-specific addition "...MT()" including adhoc target - used by bridge 
+  Error addRequestMT(ModbusMessage msg, uint32_t token, IPAddress targetHost, uint16_t targetPort);
+  ModbusMessage syncRequestMT(ModbusMessage msg, uint32_t token, IPAddress targetHost, uint16_t targetPort);
+
+  // addToQueue: send freshly created request to queue
+  bool addToQueue(uint32_t token, ModbusMessage request, TargetHost target, bool syncReq = false);
+
+  // handleConnection: worker task method
+  static void handleConnection(ModbusClientTCP *instance);
+#if IS_LINUX
+  static void *pHandle(void *p);
+#endif
+
+  // send: send request via Client connection
+  void send(RequestEntry *request);
+
+  // receive: get response via Client connection
+  ModbusMessage receive(RequestEntry *request);
+
+  void isInstance() { return; }   // make class instantiable
+  queue<RequestEntry *> requests;   // Queue to hold requests to be processed
+  #if USE_MUTEX
+  mutex qLock;                    // Mutex to protect queue
+  #endif
+  Client& MT_client;              // Client reference for Internet connections (EthernetClient or WifiClient)
+  TargetHost MT_lastTarget;       // last used server
+  TargetHost MT_target;           // Description of target server
+  uint32_t MT_defaultTimeout;     // Standard timeout value taken if no dedicated was set
+  uint32_t MT_defaultInterval;    // Standard interval value taken if no dedicated was set
+  uint16_t MT_qLimit;             // Maximum number of requests to accept in queue
+
+  // Let any ModbusBridge class use protected members
+  template<typename SERVERCLASS> friend class ModbusBridge;
+};
+
+#endif  // HAS_FREERTOS
+
+#endif  // INCLUDE GUARD
diff --git a/lib/eModbus/src/ModbusClientTCPasync.cpp b/lib/eModbus/src/ModbusClientTCPasync.cpp
new file mode 100644
index 000000000..163d552a0
--- /dev/null
+++ b/lib/eModbus/src/ModbusClientTCPasync.cpp
@@ -0,0 +1,401 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusClientTCPasync.h"
+#define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+// #undef LOCAL_LOG_LEVEL
+#include "Logging.h"
+
+ModbusClientTCPasync::ModbusClientTCPasync(IPAddress address, uint16_t port, uint16_t queueLimit) :
+  ModbusClient(),
+  txQueue(),
+  rxQueue(),
+  MTA_client(),
+  MTA_timeout(DEFAULTTIMEOUT),
+  MTA_idleTimeout(DEFAULTIDLETIME),
+  MTA_qLimit(queueLimit),
+  MTA_maxInflightRequests(queueLimit),
+  MTA_lastActivity(0),
+  MTA_state(DISCONNECTED),
+  MTA_host(address),
+  MTA_port(port)
+    {
+      // attach all handlers on async tcp events
+      MTA_client.onConnect([](void* i, AsyncClient* c) { (static_cast<ModbusClientTCPasync*>(i))->onConnected(); }, this);
+      MTA_client.onDisconnect([](void* i, AsyncClient* c) { (static_cast<ModbusClientTCPasync*>(i))->onDisconnected(); }, this);
+      MTA_client.onError([](void* i, AsyncClient* c, int8_t error) { (static_cast<ModbusClientTCPasync*>(i))->onACError(c, error); }, this);
+      // MTA_client.onTimeout([](void* i, AsyncClient* c, uint32_t time) { (static_cast<ModbusClientTCPasync*>(i))->onTimeout(time); }, this);
+      // MTA_client.onAck([](void* i, AsyncClient* c, size_t len, uint32_t time) { (static_cast<ModbusClientTCPasync*>(i))->onAck(len, time); }, this);
+      MTA_client.onData([](void* i, AsyncClient* c, void* data, size_t len) { (static_cast<ModbusClientTCPasync*>(i))->onPacket(static_cast<uint8_t*>(data), len); }, this);
+      MTA_client.onPoll([](void* i, AsyncClient* c) { (static_cast<ModbusClientTCPasync*>(i))->onPoll(); }, this);
+
+      // disable nagle algorithm ref Modbus spec
+      MTA_client.setNoDelay(true);
+    }
+
+// Destructor: clean up queue, task etc.
+ModbusClientTCPasync::~ModbusClientTCPasync() {
+  // Clean up queue
+  {
+    // Safely lock access
+    LOCK_GUARD(lock1, qLock);
+    LOCK_GUARD(lock2, sLock);
+    // Delete all elements from queues
+    while (!txQueue.empty()) {
+      delete txQueue.front();
+      txQueue.pop_front();
+    }
+    for (auto it = rxQueue.cbegin(); it != rxQueue.cend();/* no increment */) {
+      delete it->second;
+      it = rxQueue.erase(it);
+    }
+  }
+  // force close client
+  MTA_client.close(true);
+}
+
+// optionally manually connect to modbus server. Otherwise connection will be made upon first request
+void ModbusClientTCPasync::connect() {
+  LOG_D("connecting\n");
+  LOCK_GUARD(lock1, sLock);
+  // only connect if disconnected
+  if (MTA_state == DISCONNECTED) {
+    MTA_state = CONNECTING;
+    MTA_client.connect(MTA_host, MTA_port);
+  }
+}
+
+// connect to another modbus server.
+void ModbusClientTCPasync::connect(IPAddress host, uint16_t port) {
+  // First disconnect, if connected
+  disconnect(true);
+  // Set new host and port
+  MTA_host = host;
+  MTA_port = port;
+  connect();
+}
+
+// manually disconnect from modbus server. Connection will also auto close after idle time
+void ModbusClientTCPasync::disconnect(bool force) {
+  LOG_D("disconnecting\n");
+  MTA_client.close(force);
+}
+
+// Set timeout value
+void ModbusClientTCPasync::setTimeout(uint32_t timeout) {
+  MTA_timeout = timeout;
+}
+
+// Set idle timeout value (time before connection auto closes after being idle)
+void ModbusClientTCPasync::setIdleTimeout(uint32_t timeout) {
+  MTA_idleTimeout = timeout;
+}
+
+void ModbusClientTCPasync::setMaxInflightRequests(uint32_t maxInflightRequests) {
+  MTA_maxInflightRequests = maxInflightRequests;
+}
+
+// Remove all pending request from queue
+void ModbusClientTCPasync::clearQueue()
+{
+  LOCK_GUARD(lock1, qLock);
+  LOCK_GUARD(lock2, sLock);
+  // Delete all elements from queues
+  while (!txQueue.empty()) {
+    delete txQueue.front();
+    txQueue.pop_front();
+  }
+}
+
+// Base addRequest for preformatted ModbusMessage and last set target
+Error ModbusClientTCPasync::addRequestM(ModbusMessage msg, uint32_t token) {
+  Error rc = SUCCESS;        // Return value
+
+  // Add it to the queue, if valid
+  if (msg) {
+    // Queue add successful?
+    if (!addToQueue(token, msg)) {
+      // No. Return error after deleting the allocated request.
+      rc = REQUEST_QUEUE_FULL;
+    }
+  }
+
+  LOG_D("Add TCP request result: %02X\n", rc);
+  return rc;
+}
+
+// Base syncRequest follows the same pattern
+ModbusMessage ModbusClientTCPasync::syncRequestM(ModbusMessage msg, uint32_t token) {
+  ModbusMessage response;
+
+  if (msg) {
+    // Queue add successful?
+    if (!addToQueue(token, msg, true)) {
+      // No. Return error after deleting the allocated request.
+      response.setError(msg.getServerID(), msg.getFunctionCode(), REQUEST_QUEUE_FULL);
+    } else {
+      // Request is queued - wait for the result.
+      response = waitSync(msg.getServerID(), msg.getFunctionCode(), token);
+    }
+  } else {
+    response.setError(msg.getServerID(), msg.getFunctionCode(), EMPTY_MESSAGE);
+  }
+  return response;
+}
+
+// addToQueue: send freshly created request to queue
+bool ModbusClientTCPasync::addToQueue(int32_t token, ModbusMessage request, bool syncReq) {
+  // Did we get one?
+  if (request) {
+    LOCK_GUARD(lock1, qLock);
+    if (txQueue.size() + rxQueue.size() < MTA_qLimit) {
+      HEXDUMP_V("Enqueue", request.data(), request.size());
+      RequestEntry *re = new RequestEntry(token, request, syncReq);
+      if (!re) return false;  //TODO: proper error returning in case allocation fails
+      // inject proper transactionID
+      re->head.transactionID = messageCount++;
+      re->head.len = request.size();
+      // if we're already connected, try to send and push to rxQueue
+      // or else push to txQueue and (re)connect
+      if (MTA_state == CONNECTED && send(re)) {
+        re->sentTime = millis();
+        rxQueue[re->head.transactionID] = re;
+      } else {
+        txQueue.push_back(re);
+        if (MTA_state == DISCONNECTED) {
+          connect();
+        }
+      }
+      return true;
+    }
+    LOG_E("queue is full\n");
+  }
+  return false;
+}
+
+void ModbusClientTCPasync::onConnected() {
+  LOG_D("connected\n");
+  LOCK_GUARD(lock1, sLock);
+  MTA_state = CONNECTED;
+  MTA_lastActivity = millis();
+  // from now on onPoll will be called every 500 msec
+}
+
+void ModbusClientTCPasync::onDisconnected() {
+  LOG_D("disconnected\n");
+  LOCK_GUARD(lock1, sLock);
+  MTA_state = DISCONNECTED;
+
+  // empty queue on disconnect, calling errorcode on every waiting request
+  LOCK_GUARD(lock2, qLock);
+  while (!txQueue.empty()) {
+    RequestEntry* r = txQueue.front();
+    if (onError) {
+      onError(IP_CONNECTION_FAILED, r->token);
+    }
+    delete r;
+    txQueue.pop_front();
+  }
+  while (!rxQueue.empty()) {
+    RequestEntry *r = rxQueue.begin()->second;
+    if (onError) {
+      onError(IP_CONNECTION_FAILED, r->token);
+    }
+    delete r;
+    rxQueue.erase(rxQueue.begin());
+  }
+}
+
+
+void ModbusClientTCPasync::onACError(AsyncClient* c, int8_t error) {
+  // onDisconnect will alse be called, so nothing to do here
+  LOG_W("TCP error: %s\n", c->errorToString(error));
+}
+
+/*
+void onTimeout(uint32_t time) {
+  // timeOut is handled by onPoll or onDisconnect
+}
+
+void onAck(size_t len, uint32_t time) {
+  // assuming we don't need this
+}
+*/
+void ModbusClientTCPasync::onPacket(uint8_t* data, size_t length) {
+  LOG_D("packet received (len:%d)\n", length);
+  // reset idle timeout
+  MTA_lastActivity = millis();
+
+  if (length) {
+    LOG_D("parsing (len:%d)\n", length + 1);
+  }
+  while (length > 0) {
+    RequestEntry* request = nullptr;
+    ModbusMessage* response = nullptr;
+    uint16_t transactionID = 0;
+    uint16_t protocolID = 0;
+    uint16_t messageLength = 0;
+    bool isOkay = false;
+
+    // 1. Check for valid modbus message
+
+    // MBAP header is 6 bytes, we can't do anything with less
+    // total message should fit MBAP plus remaining bytes (in data[4], data[5])
+    if (length > 6) {
+      transactionID = (data[0] << 8) | data[1];
+      protocolID = (data[2] << 8) | data[3];
+      messageLength = (data[4] << 8) | data[5];
+      if (protocolID == 0 &&
+        length >= (uint32_t)messageLength + 6 &&
+        messageLength < 256) {
+        response = new ModbusMessage(messageLength);
+        response->add(&data[6], messageLength);
+        LOG_D("packet validated (len:%d)\n", messageLength);
+
+        // on next iteration: adjust remaining length and pointer to data
+        length -= 6 + messageLength;
+        data += 6 + messageLength;
+        isOkay = true;
+      }
+    }
+
+    if (!isOkay) {
+      // invalid packet, abort function
+      LOG_W("packet invalid\n");
+      return;
+    } else {
+      // 2. we got a valid response, match with a request
+      LOCK_GUARD(lock1, qLock);
+      auto i = rxQueue.find(transactionID);
+      if (i != rxQueue.end()) {
+        // found it, handle it and stop iterating
+        request = i->second;
+        i = rxQueue.erase(i);
+        LOG_D("matched request\n");
+      } else {
+        // TCP packet did not yield valid modbus response, abort function
+        LOG_W("no matching request found\n");
+        return;
+      }
+    }
+
+    // 3. we have a valid request and a valid response, call appropriate callback
+    if (request) {
+      // compare request with response
+      Error error = SUCCESS;
+      if (request->msg.getFunctionCode() != (response->getFunctionCode() & 0x7F)) {
+        error = FC_MISMATCH;
+      } else if (request->msg.getServerID() != response->getServerID()) {
+        error = SERVER_ID_MISMATCH;
+      } else {
+        error = response->getError();
+      }
+
+      if (error != SUCCESS) {
+        LOCK_GUARD(errorCntLock, countAccessM);
+        errorCount++;
+      }
+
+      if (request->isSyncRequest) {
+        {
+          LOCK_GUARD(sL ,syncRespM);
+          syncResponse[request->token] = *response;
+        }
+      } else if (onResponse) {
+        onResponse(*response, request->token);
+      } else {
+        if (error == SUCCESS) {
+          if (onData) {
+            onData(*response, request->token);
+          }
+        } else {
+          if (onError) {
+            onError(response->getError(), request->token);
+          }
+        }
+      }
+      delete request;
+    }
+    delete response;
+
+  }  // end processing of incoming data
+
+  // check if we have to send the next request
+  LOCK_GUARD(lock1, qLock);
+  handleSendingQueue();
+}
+
+void ModbusClientTCPasync::onPoll() {
+  {
+  LOCK_GUARD(lock1, qLock);
+
+  // try to send whatever is waiting
+  handleSendingQueue();
+
+  // next check if timeout has struck for oldest request
+  if (!rxQueue.empty()) {
+    RequestEntry* request = rxQueue.begin()->second;
+    if (millis() - request->sentTime > MTA_timeout) {
+      LOG_D("request timeouts (now:%lu-sent:%u)\n", millis(), request->sentTime);
+      // oldest element timeouts, call onError and clean up
+      if (onError) {
+        // Handle timeout error
+        onError(TIMEOUT, request->token);
+      }
+      delete request;
+      rxQueue.erase(rxQueue.begin());
+    }
+  }
+    
+  }  // end lockguard scope
+
+  // if nothing happened during idle timeout, gracefully close connection
+  if (millis() - MTA_lastActivity > MTA_idleTimeout) {
+    disconnect();
+  }
+}
+
+void ModbusClientTCPasync::handleSendingQueue() {
+  // ATTENTION: This method does not have a lock guard.
+  // Calling sites must assure shared resources are protected
+  // by mutex.
+
+  // try to send everything we have waiting
+  std::list<RequestEntry*>::iterator it = txQueue.begin();
+  while (it != txQueue.end()) {
+    // get the actual element
+    if (send(*it)) {
+      // after sending, update timeout value, add to other queue and remove from this queue
+      (*it)->sentTime = millis();
+      rxQueue[(*it)->head.transactionID] = (*it);      // push request to other queue
+      it = txQueue.erase(it);  // remove from toSend queue and point i to next request
+    } else {
+      // sending didn't succeed, try next request
+      ++it;
+    }
+  }
+}
+
+bool ModbusClientTCPasync::send(RequestEntry* re) {
+  // ATTENTION: This method does not have a lock guard.
+  // Calling sites must assure shared resources are protected
+  // by mutex.
+
+  if (rxQueue.size() >= MTA_maxInflightRequests) {
+    return false;
+  }
+
+  // check if TCP client is able to send
+  if (MTA_client.space() > ((uint32_t)re->msg.size() + 6)) {
+    // Write TCP header first
+    MTA_client.add(reinterpret_cast<const char *>((const uint8_t *)(re->head)), 6, ASYNC_WRITE_FLAG_COPY);
+    // Request comes next
+    MTA_client.add(reinterpret_cast<const char*>(re->msg.data()), re->msg.size(), ASYNC_WRITE_FLAG_COPY);
+    // done
+    MTA_client.send();
+    LOG_D("request sent (msgid:%d)\n", re->head.transactionID);
+    return true;
+  }
+  return false;
+}
diff --git a/lib/eModbus/src/ModbusClientTCPasync.h b/lib/eModbus/src/ModbusClientTCPasync.h
new file mode 100644
index 000000000..a1f2aeea0
--- /dev/null
+++ b/lib/eModbus/src/ModbusClientTCPasync.h
@@ -0,0 +1,158 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_CLIENT_TCP_ASYNC_H
+#define _MODBUS_CLIENT_TCP_ASYNC_H
+#include <Arduino.h>
+#if defined ESP32
+#include <AsyncTCP.h>
+#elif defined ESP8266
+#include <ESPAsyncTCP.h>
+#endif
+#include "options.h"
+#include "ModbusMessage.h"
+#include "ModbusClient.h"
+#include <list>
+#include <map>
+#include <vector>
+#if USE_MUTEX
+#include <mutex>      // NOLINT
+#endif
+
+using std::vector;
+
+#define DEFAULTTIMEOUT 10000
+#define DEFAULTIDLETIME 60000
+
+class ModbusClientTCPasync : public ModbusClient {
+public:
+  // Constructor takes address and port
+  explicit ModbusClientTCPasync(IPAddress address, uint16_t port = 502, uint16_t queueLimit = 100);
+
+  // Destructor: clean up queue, task etc.
+  ~ModbusClientTCPasync();
+
+  // optionally manually connect to modbus server. Otherwise connection will be made upon first request
+  void connect();
+  // Connect to another Modbus server
+  void connect(IPAddress host, uint16_t port = 502);
+
+  // manually disconnect from modbus server. Connection will also auto close after idle time
+  void disconnect(bool force = false);
+
+  // Set timeout value
+  void setTimeout(uint32_t timeout);
+
+  // Set idle timeout value (time before connection auto closes after being idle)
+  void setIdleTimeout(uint32_t timeout);
+
+  // Set maximum amount of messages awaiting a response. Subsequent messages will be queued.
+  void setMaxInflightRequests(uint32_t maxInflightRequests);
+
+// Remove all pending request from queue
+  void clearQueue();
+
+protected:
+
+  // class describing the TCP header of Modbus packets
+  class ModbusTCPhead {
+  public:
+    ModbusTCPhead() :
+    transactionID(0),
+    protocolID(0),
+    len(0) {}
+
+    ModbusTCPhead(uint16_t tid, uint16_t pid, uint16_t _len) :
+    transactionID(tid),
+    protocolID(pid),
+    len(_len) {}
+
+    uint16_t transactionID;     // Caller-defined identification
+    uint16_t protocolID;        // const 0x0000
+    uint16_t len;               // Length of remainder of TCP packet
+
+    inline explicit operator const uint8_t *() {
+      uint8_t *cp = headRoom;
+      *cp++ = (transactionID >> 8) & 0xFF;
+      *cp++ = transactionID  & 0xFF;
+      *cp++ = (protocolID >> 8) & 0xFF;
+      *cp++ = protocolID  & 0xFF;
+      *cp++ = (len >> 8) & 0xFF;
+      *cp++ = len  & 0xFF;
+      return headRoom;
+    }
+
+    inline ModbusTCPhead& operator= (ModbusTCPhead& t) {
+      transactionID = t.transactionID;
+      protocolID    = t.protocolID;
+      len           = t.len;
+      return *this;
+    }
+
+  protected:
+    uint8_t headRoom[6];        // Buffer to hold MSB-first TCP header
+  };
+
+  struct RequestEntry {
+    uint32_t token;
+    ModbusMessage msg;
+    ModbusTCPhead head;
+    uint32_t sentTime;
+    bool isSyncRequest;
+    RequestEntry(uint32_t t, ModbusMessage m, bool syncReq = false) :
+      token(t),
+      msg(m),
+      head(ModbusTCPhead()),
+      sentTime(0),
+      isSyncRequest(syncReq) {}
+  };
+
+  // Base addRequest and syncRequest both must be present
+  Error addRequestM(ModbusMessage msg, uint32_t token);
+  ModbusMessage syncRequestM(ModbusMessage msg, uint32_t token);
+
+  // addToQueue: send freshly created request to queue
+  bool addToQueue(int32_t token, ModbusMessage request, bool syncReq = false);
+
+  // send: send request via Client connection
+  bool send(RequestEntry *request);
+
+  // receive: get response via Client connection
+  // TCPResponse* receive(uint8_t* data, size_t length);
+
+  void isInstance() { return; }     // make class instantiable
+
+  // TCP handling code, all static taking a class instancs as param
+  void onConnected();
+  void onDisconnected();
+  void onACError(AsyncClient* c, int8_t error);
+  // void onTimeout(uint32_t time);
+  // void onAck(size_t len, uint32_t time);
+  void onPacket(uint8_t* data, size_t length);
+  void onPoll();
+  void handleSendingQueue();
+
+  std::list<RequestEntry*> txQueue;           // Queue to hold requests to be sent
+  std::map<uint16_t, RequestEntry*> rxQueue;  // Queue to hold requests to be processed
+  #if USE_MUTEX
+  std::mutex sLock;                         // Mutex to protect state
+  std::mutex qLock;                         // Mutex to protect queues
+  #endif
+
+  AsyncClient MTA_client;           // Async TCP client
+  uint32_t MTA_timeout;             // Standard timeout value taken
+  uint32_t MTA_idleTimeout;         // Standard timeout value taken
+  uint16_t MTA_qLimit;              // Maximum number of requests to accept in queue
+  uint32_t MTA_maxInflightRequests; // Maximum number of inflight requests
+  uint32_t MTA_lastActivity;        // Last time there was activity (disabled when queues are not empty)
+  enum {
+    DISCONNECTED,
+    CONNECTING,
+    CONNECTED
+  } MTA_state;                      // TCP connection state
+  IPAddress MTA_host;
+  uint16_t MTA_port;
+};
+
+#endif
diff --git a/lib/eModbus/src/ModbusError.h b/lib/eModbus/src/ModbusError.h
new file mode 100644
index 000000000..8f4c3a1a9
--- /dev/null
+++ b/lib/eModbus/src/ModbusError.h
@@ -0,0 +1,138 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_ERROR_H
+#define _MODBUS_ERROR_H
+#include "ModbusTypeDefs.h"
+
+using namespace Modbus;  // NOLINT
+
+class ModbusError {
+public:
+  // Constructor with error code
+  inline explicit ModbusError(Error e) : err(e) {}
+  // Empty constructor defaults to 0
+  inline ModbusError() : err(SUCCESS) {}
+  // Assignment operators
+  inline ModbusError& operator=(const ModbusError& e) { err = e.err; return *this; }
+  inline ModbusError& operator=(const Error e) { err = e; return *this; }
+  // Copy constructor
+  inline ModbusError(const ModbusError& m) : err(m.err) {}
+  // Equality comparison
+  inline bool operator==(const ModbusError& m) { return (err == m.err); }
+  inline bool operator==(const Error e) { return (err == e); }
+  // Inequality comparison
+  inline bool operator!=(const ModbusError& m) { return (err != m.err); }
+  inline bool operator!=(const Error e) { return (err != e); }
+  inline explicit operator Error() { return err; }
+  inline operator int() { return static_cast<int>(err); }
+
+#ifndef MINIMAL
+  inline explicit operator const char *() { return getText(err); }
+#endif
+
+private:
+  Error err;          // The error code
+
+#ifndef MINIMAL
+// Return error as static text
+  inline static const char *getText(Error err) {
+    switch (err) {
+    case SUCCESS               : // 0x00,
+      return "Success";
+      break;
+    case ILLEGAL_FUNCTION      : // 0x01,
+      return "Illegal function code";
+      break;
+    case ILLEGAL_DATA_ADDRESS  : // 0x02,
+      return "Illegal data address";
+      break;
+    case ILLEGAL_DATA_VALUE    : // 0x03,
+      return "Illegal data value";
+      break;
+    case SERVER_DEVICE_FAILURE : // 0x04,
+      return "Server device failure";
+      break;
+    case ACKNOWLEDGE           : // 0x05,
+      return "Acknowledge";
+      break;
+    case SERVER_DEVICE_BUSY    : // 0x06,
+      return "Server device busy";
+      break;
+    case NEGATIVE_ACKNOWLEDGE  : // 0x07,
+      return "Negative acknowledge";
+      break;
+    case MEMORY_PARITY_ERROR   : // 0x08,
+      return "Memory parity error";
+      break;
+    case GATEWAY_PATH_UNAVAIL  : // 0x0A,
+      return "Gateway path unavailable";
+      break;
+    case GATEWAY_TARGET_NO_RESP: // 0x0B,
+      return "Gateway target not responding";
+      break;
+    case TIMEOUT               : // 0xE0,
+      return "Timeout";
+      break;
+    case INVALID_SERVER        : // 0xE1,
+      return "Invalid server";
+      break;
+    case CRC_ERROR             : // 0xE2, // only for Modbus-RTU
+      return "CRC check error";
+      break;
+    case FC_MISMATCH           : // 0xE3,
+      return "Function code mismatch";
+      break;
+    case SERVER_ID_MISMATCH    : // 0xE4,
+      return "Server ID mismatch";
+      break;
+    case PACKET_LENGTH_ERROR   : // 0xE5,
+      return "Packet length error";
+      break;
+    case PARAMETER_COUNT_ERROR : // 0xE6,
+      return "Wrong # of parameters";
+      break;
+    case PARAMETER_LIMIT_ERROR : // 0xE7,
+      return "Parameter out of bounds";
+      break;
+    case REQUEST_QUEUE_FULL    : // 0xE8,
+      return "Request queue full";
+      break;
+    case ILLEGAL_IP_OR_PORT    : // 0xE9,
+      return "Illegal IP or port";
+      break;
+    case IP_CONNECTION_FAILED  : // 0xEA,
+      return "IP connection failed";
+      break;
+    case TCP_HEAD_MISMATCH     : // 0xEB,
+      return "TCP header mismatch";
+      break;
+    case EMPTY_MESSAGE         : // 0xEC,
+      return "Incomplete request";
+      break;
+    case ASCII_FRAME_ERR       : // 0xED,
+      return "Invalid ASCII frame";
+      break;
+    case ASCII_CRC_ERR         : // 0xEE,
+      return "Invalid ASCII CRC";
+      break;
+    case ASCII_INVALID_CHAR    : // 0xEF,
+      return "Invalid ASCII character";
+      break;
+    case BROADCAST_ERROR       : // 0xF0,
+      return "Broadcast data invalid";
+      break;
+    case UNDEFINED_ERROR       : // 0xFF  // otherwise uncovered communication error
+    default:
+      return "Unspecified error";
+      break;
+    }
+    return "What?";
+  }
+
+#endif
+
+};
+
+#endif
diff --git a/lib/eModbus/src/ModbusMessage.cpp b/lib/eModbus/src/ModbusMessage.cpp
new file mode 100644
index 000000000..1ed48360d
--- /dev/null
+++ b/lib/eModbus/src/ModbusMessage.cpp
@@ -0,0 +1,705 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusMessage.h"
+#undef LOCAL_LOG_LEVEL
+// #define LOCAL_LOG_LEVEL LOG_LEVEL_ERROR
+#include "Logging.h"
+
+// Default Constructor - takes optional size of MM_data to allocate memory
+ModbusMessage::ModbusMessage(uint16_t dataLen) {
+  if (dataLen) MM_data.reserve(dataLen);
+}
+
+// Special message Constructor - takes a std::vector<uint8_t>
+ModbusMessage::ModbusMessage(std::vector<uint8_t> s) :
+MM_data(s) { }
+
+// Destructor
+ModbusMessage::~ModbusMessage() { 
+  // If paranoid, one can use the below :D
+  // std::vector<uint8_t>().swap(MM_data);
+}
+
+// Assignment operator
+ModbusMessage& ModbusMessage::operator=(const ModbusMessage& m) {
+  // Do anything only if not self-assigning
+  if (this != &m) {
+    // Copy data from source to target
+    MM_data = m.MM_data;
+  }
+  return *this;
+}
+
+#ifndef NO_MOVE
+  // Move constructor
+ModbusMessage::ModbusMessage(ModbusMessage&& m) {
+  MM_data = std::move(m.MM_data);
+}
+  
+	// Move assignment
+ModbusMessage& ModbusMessage::operator=(ModbusMessage&& m) {
+  MM_data = std::move(m.MM_data);
+  return *this;
+}
+#endif
+
+// Copy constructor
+ModbusMessage::ModbusMessage(const ModbusMessage& m) :
+  MM_data(m.MM_data) { }
+
+// Equality comparison
+bool ModbusMessage::operator==(const ModbusMessage& m) {
+  // Prevent self-compare
+  if (this == &m) return true;
+  // If size is different, we assume inequality
+  if (MM_data.size() != m.MM_data.size()) return false;
+  // We will compare bytes manually - for uint8_t it should work out-of-the-box,
+  // but the data type might be changed later.
+  // If we find a difference byte, we found inequality
+  for (uint16_t i = 0; i < MM_data.size(); ++i) {
+    if (MM_data[i] != m.MM_data[i]) return false;
+  }
+  // Both tests passed ==> equality
+  return true;
+}
+
+// Inequality comparison
+bool ModbusMessage::operator!=(const ModbusMessage& m) {
+  return (!(*this == m));
+}
+
+// Conversion to bool
+ModbusMessage::operator bool() {
+  if (MM_data.size() >= 2) return true;
+  return false;
+}
+
+// Exposed methods of std::vector
+const uint8_t *ModbusMessage::data() { return MM_data.data(); }
+uint16_t       ModbusMessage::size() { return MM_data.size(); }
+void           ModbusMessage::push_back(const uint8_t& val) { MM_data.push_back(val); }
+void           ModbusMessage::clear() { MM_data.clear(); }
+// provide restricted operator[] interface
+uint8_t  ModbusMessage::operator[](uint16_t index) const {
+  if (index < MM_data.size()) {
+    return MM_data[index];
+  }
+  LOG_W("Index %d out of bounds (>=%d).\n", index, MM_data.size());
+  return 0;
+}
+// Resize internal MM_data
+uint16_t ModbusMessage::resize(uint16_t newSize) { 
+  MM_data.resize(newSize); 
+  return MM_data.size(); 
+}
+
+// Add append() for two ModbusMessages or a std::vector<uint8_t> to be appended
+void ModbusMessage::append(ModbusMessage& m) { 
+  MM_data.reserve(size() + m.size()); 
+  MM_data.insert(MM_data.end(), m.begin(), m.end()); 
+}
+
+void ModbusMessage::append(std::vector<uint8_t>& m) { 
+  MM_data.reserve(size() + m.size()); 
+  MM_data.insert(MM_data.end(), m.begin(), m.end()); 
+}
+
+uint8_t ModbusMessage::getServerID() const {
+  // Only if we have data and it is at least as long to fit serverID and function code, return serverID
+  if (MM_data.size() >= 2) { return MM_data[0]; }
+  // Else return 0 - normally the Broadcast serverID, but we will not support that. Full stop. :-D
+  return 0;
+}
+
+// Get MM_data[0] (server ID) and MM_data[1] (function code)
+uint8_t ModbusMessage::getFunctionCode() const {
+  // Only if we have data and it is at least as long to fit serverID and function code, return FC
+  if (MM_data.size() >= 2) { return MM_data[1]; }
+  // Else return 0 - which is no valid Modbus FC.
+  return 0;
+}
+
+// getError() - returns error code
+Error ModbusMessage::getError() const {
+  // Do we have data long enough?
+  if (MM_data.size() > 2) {
+    // Yes. Does it indicate an error?
+    if (MM_data[1] & 0x80)
+    {
+      // Yes. Get it.
+      return static_cast<Modbus::Error>(MM_data[2]);
+    }
+  }
+  // Default: everything OK - SUCCESS
+  return SUCCESS;
+}
+
+// Modbus data manipulation
+void    ModbusMessage::setServerID(uint8_t serverID) {
+  // We accept here that [0] may allocate a byte!
+  if (MM_data.empty()) {
+    MM_data.reserve(3);  // At least an error message should fit
+  }
+  MM_data[0] = serverID;
+}
+
+void    ModbusMessage::setFunctionCode(uint8_t FC) {
+  // We accept here that [0], [1] may allocate bytes!
+  if (MM_data.empty()) {
+    MM_data.reserve(3);  // At least an error message should fit
+  }
+  // No serverID set yet? use a 0 to initialize it to an error-generating value
+  if (MM_data.size() < 2) MM_data[0] = 0; // intentional invalid server ID!
+  MM_data[1] = FC;
+}
+
+// add() variant to copy a buffer into MM_data. Returns updated size
+uint16_t ModbusMessage::add(const uint8_t *arrayOfBytes, uint16_t count) {
+  // Copy it
+  while (count--) {
+    MM_data.push_back(*arrayOfBytes++);
+  }
+  // Return updated size (logical length of message so far)
+  return MM_data.size();
+}
+
+// determineFloatOrder: calculate the sequence of bytes in a float value
+uint8_t ModbusMessage::determineFloatOrder() {
+  constexpr uint8_t floatSize = sizeof(float);
+  // Only do it if not done yet
+  if (floatOrder[0] == 0xFF) {
+    // We need to calculate it.
+    // This will only work for 32bit floats, so check that
+    if (floatSize != 4) {
+      // OOPS! we cannot proceed.
+      LOG_E("Oops. float seems to be %d bytes wide instead of 4.\n", floatSize);
+      return 0;
+    }
+
+    uint32_t i = 77230;                             // int value to go into a float without rounding error
+    float f = i;                                    // assign it
+    uint8_t *b = (uint8_t *)&f;                     // Pointer to bytes of f
+    uint8_t expect[floatSize] = { 0x47, 0x96, 0xd7, 0x00 }; // IEEE754 representation 
+    uint8_t matches = 0;                            // number of bytes successfully matched
+     
+    // Loop over the bytes of the expected sequence
+    for (uint8_t inx = 0; inx < floatSize; ++inx) {
+      // Loop over the real bytes of f
+      for (uint8_t trg = 0; trg < floatSize; ++trg) {
+        if (expect[inx] == b[trg]) {
+          floatOrder[inx] = trg;
+          matches++;
+          break;
+        }
+      }
+    }
+
+    // All bytes found?
+    if (matches != floatSize) {
+      // No! There is something fishy...
+      LOG_E("Unable to determine float byte order (matched=%d of %d)\n", matches, floatSize);
+      floatOrder[0] = 0xFF;
+      return 0;
+    } else {
+      HEXDUMP_V("floatOrder", floatOrder, floatSize);
+    }
+  }
+  return floatSize;
+}
+
+// determineDoubleOrder: calculate the sequence of bytes in a double value
+uint8_t ModbusMessage::determineDoubleOrder() {
+  constexpr uint8_t doubleSize = sizeof(double);
+  // Only do it if not done yet
+  if (doubleOrder[0] == 0xFF) {
+    // We need to calculate it.
+    // This will only work for 64bit doubles, so check that
+    if (doubleSize != 8) {
+      // OOPS! we cannot proceed.
+      LOG_E("Oops. double seems to be %d bytes wide instead of 8.\n", doubleSize);
+      return 0;
+    }
+
+    uint64_t i = 5791007487489389;                  // int64 value to go into a double without rounding error
+    double f = i;                                   // assign it
+    uint8_t *b = (uint8_t *)&f;                     // Pointer to bytes of f
+    uint8_t expect[doubleSize] = { 0x43, 0x34, 0x92, 0xE4, 0x00, 0x2E, 0xF5, 0x6D }; // IEEE754 representation 
+    uint8_t matches = 0;                            // number of bytes successfully matched
+     
+    // Loop over the bytes of the expected sequence
+    for (uint8_t inx = 0; inx < doubleSize; ++inx) {
+      // Loop over the real bytes of f
+      for (uint8_t trg = 0; trg < doubleSize; ++trg) {
+        if (expect[inx] == b[trg]) {
+          doubleOrder[inx] = trg;
+          matches++;
+          break;
+        }
+      }
+    }
+
+    // All bytes found?
+    if (matches != doubleSize) {
+      // No! There is something fishy...
+      LOG_E("Unable to determine double byte order (matched=%d of %d)\n", matches, doubleSize);
+      doubleOrder[0] = 0xFF;
+      return 0;
+    } else {
+      HEXDUMP_V("doubleOrder", doubleOrder, doubleSize);
+    }
+  }
+  return doubleSize;
+}
+
+// swapFloat() and swapDouble() will re-order the bytes of a float or double value
+// according a user-given pattern
+float ModbusMessage::swapFloat(float& f, int swapRule) {
+  LOG_V("swap float, swapRule=%02X\n", swapRule);
+  // Make a byte pointer to the given float
+  uint8_t *src = (uint8_t *)&f;
+  // Define a "work bench" float and byte pointer to it
+  float interim;
+  uint8_t *dst = (uint8_t *)&interim;
+  // Loop over all bytes of a float
+  for (uint8_t i = 0; i < sizeof(float); ++i) {
+    // Get i-th byte from the spot the swap table tells
+    // (only the first 4 tables are valid for floats)
+    LOG_V("dst[%d] = src[%d]\n", i, swapTables[swapRule & 0x03][i]);
+    dst[i] = src[swapTables[swapRule & 0x03][i]];
+    // Does the swar rule require nibble swaps?
+    if (swapRule & 0x08) {
+      // Yes, it does. 
+      uint8_t nib = ((dst[i] & 0x0f) << 4) | ((dst[i] >> 4) & 0x0F);
+      dst[i] = nib;
+    }
+  }
+  // Save and return result
+  f = interim;
+  return interim;
+}
+
+double ModbusMessage::swapDouble(double& f, int swapRule) {
+  LOG_V("swap double, swapRule=%02X\n", swapRule);
+  // Make a byte pointer to the given double
+  uint8_t *src = (uint8_t *)&f;
+  // Define a "work bench" double and byte pointer to it
+  double interim;
+  uint8_t *dst = (uint8_t *)&interim;
+  // Loop over all bytes of a double
+  for (uint8_t i = 0; i < sizeof(double); ++i) {
+    // Get i-th byte from the spot the swap table tells
+    LOG_V("dst[%d] = src[%d]\n", i, swapTables[swapRule & 0x07][i]);
+    dst[i] = src[swapTables[swapRule & 0x07][i]];
+    // Does the swar rule require nibble swaps?
+    if (swapRule & 0x08) {
+      // Yes, it does. 
+      uint8_t nib = ((dst[i] & 0x0f) << 4) | ((dst[i] >> 4) & 0x0F);
+      dst[i] = nib;
+    }
+  }
+  // Save and return result
+  f = interim;
+  return interim;
+}
+
+// add() variant for a vector of uint8_t
+uint16_t ModbusMessage::add(vector<uint8_t> v) {
+  for (auto& b: v) {
+    MM_data.push_back(b);
+  }
+  return MM_data.size();
+}
+
+// add() variants for float and double values
+// values will be added in IEEE754 byte sequence (MSB first)
+uint16_t ModbusMessage::add(float v, int swapRule) {
+  // First check if we need to determine byte order
+  LOG_V("add float, swapRule=%02X\n", swapRule);
+  HEXDUMP_V("float", (uint8_t *)&v, sizeof(float));
+  if (determineFloatOrder()) {
+    // If we get here, the floatOrder is known
+    float interim = 0;
+    uint8_t *dst = (uint8_t *)&interim;
+    uint8_t *src = (uint8_t *)&v;
+    // Put out the bytes of v in normalized sequence
+    for (uint8_t i = 0; i < sizeof(float); ++i) {
+      dst[i] = src[floatOrder[i]];
+    }
+    HEXDUMP_V("normalized float", (uint8_t *)&interim, sizeof(float));
+    // Do we need to apply a swap rule?
+    if (swapRule & 0x0B) {
+      // Yes, so do it.
+      swapFloat(interim, swapRule & 0x0B);
+    }
+    HEXDUMP_V("swapped float", (uint8_t *)&interim, sizeof(float));
+    // Put out the bytes of v in normalized (and swapped) sequence
+    for (uint8_t i = 0; i < sizeof(float); ++i) {
+      MM_data.push_back(dst[i]);
+    }
+  }
+
+  return MM_data.size();
+}
+
+uint16_t ModbusMessage::add(double v, int swapRule) {
+  // First check if we need to determine byte order
+  LOG_V("add double, swapRule=%02X\n", swapRule);
+  HEXDUMP_V("double", (uint8_t *)&v, sizeof(double));
+  if (determineDoubleOrder()) {
+    // If we get here, the doubleOrder is known
+    double interim = 0;
+    uint8_t *dst = (uint8_t *)&interim;
+    uint8_t *src = (uint8_t *)&v;
+    // Put out the bytes of v in normalized sequence
+    for (uint8_t i = 0; i < sizeof(double); ++i) {
+      dst[i] = src[doubleOrder[i]];
+    }
+    HEXDUMP_V("normalized double", (uint8_t *)&interim, sizeof(double));
+    // Do we need to apply a swap rule?
+    if (swapRule & 0x0F) {
+      // Yes, so do it.
+      swapDouble(interim, swapRule & 0x0F);
+    }
+    HEXDUMP_V("swapped double", (uint8_t *)&interim, sizeof(double));
+    // Put out the bytes of v in normalized (and swapped) sequence
+    for (uint8_t i = 0; i < sizeof(double); ++i) {
+      MM_data.push_back(dst[i]);
+    }
+  }
+
+  return MM_data.size();
+}
+
+// get() variants for float and double values
+// values will be read in IEEE754 byte sequence (MSB first)
+uint16_t ModbusMessage::get(uint16_t index, float& v, int swapRule) const {
+  // First check if we need to determine byte order
+  if (determineFloatOrder()) {
+    // If we get here, the floatOrder is known
+    // Will it fit?
+    if (index <= MM_data.size() - sizeof(float)) {
+      // Yes. Get the bytes of v in normalized sequence
+      uint8_t *bytes = (uint8_t *)&v;
+      for (uint8_t i = 0; i < sizeof(float); ++i) {
+        bytes[i] = MM_data[index + floatOrder[i]];
+      }
+      HEXDUMP_V("got float", (uint8_t *)&v, sizeof(float));
+      // Do we need to apply a swap rule?
+      if (swapRule & 0x0B) {
+        // Yes, so do it.
+        swapFloat(v, swapRule & 0x0B);
+      }
+      HEXDUMP_V("got float swapped", (uint8_t *)&v, sizeof(float));
+      index += sizeof(float);
+    }
+  }
+
+  return index;
+}
+
+uint16_t ModbusMessage::get(uint16_t index, double& v, int swapRule) const {
+  // First check if we need to determine byte order
+  if (determineDoubleOrder()) {
+    // If we get here, the doubleOrder is known
+    // Will it fit?
+    if (index <= MM_data.size() - sizeof(double)) {
+      // Yes. Get the bytes of v in normalized sequence
+      uint8_t *bytes = (uint8_t *)&v;
+      for (uint8_t i = 0; i < sizeof(double); ++i) {
+        bytes[i] = MM_data[index + doubleOrder[i]];
+      }
+      HEXDUMP_V("got double", (uint8_t *)&v, sizeof(double));
+      // Do we need to apply a swap rule?
+      if (swapRule & 0x0F) {
+        // Yes, so do it.
+        swapDouble(v, swapRule & 0x0F);
+      }
+      HEXDUMP_V("got double swapped", (uint8_t *)&v, sizeof(double));
+      index += sizeof(double);
+    }
+  }
+
+  return index;
+}
+
+// get() - read a byte array of a given size into a vector<uint8_t>. Returns updated index
+uint16_t ModbusMessage::get(uint16_t index, vector<uint8_t>& v, uint8_t count) const {
+  // Clean target vector
+  v.clear();
+  // Loop until required count is complete or the source is exhausted
+  while (index < MM_data.size() && count--) {
+    v.push_back(MM_data[index++]);
+  }
+  return index;
+}
+
+// Data validation methods for the different factory calls
+// 0. serverID and function code - used by all of the below
+Error ModbusMessage::checkServerFC(uint8_t serverID, uint8_t functionCode) {
+  if (serverID == 0)      return INVALID_SERVER;   // Broadcast - not supported here
+  if (serverID > 247)     return INVALID_SERVER;   // Reserved server addresses
+  if (FCT::getType(functionCode) == FCILLEGAL)  return ILLEGAL_FUNCTION; // FC 0 does not exist
+  return SUCCESS;
+}
+
+// 1. no additional parameter (FCs 0x07, 0x0b, 0x0c, 0x11)
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode) {
+  LOG_V("Check data #1\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FC07_TYPE && ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    }
+  }
+  return returnCode;
+}
+
+// 2. one uint16_t parameter (FC 0x18)
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1) {
+  LOG_V("Check data #2\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FC18_TYPE && ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    }
+  }
+  return returnCode;
+}
+
+// 3. two uint16_t parameters (FC 0x01, 0x02, 0x03, 0x04, 0x05, 0x06)
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2) {
+  LOG_V("Check data #3\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FC01_TYPE && ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    } else {
+      switch (functionCode) {
+      case 0x01:
+      case 0x02:
+        if ((p2 > 0x7d0) || (p2 == 0)) returnCode = PARAMETER_LIMIT_ERROR;
+        break;
+      case 0x03:
+      case 0x04:
+        if ((p2 > 0x7d) || (p2 == 0)) returnCode = PARAMETER_LIMIT_ERROR;
+        break;
+      case 0x05:
+        if ((p2 != 0) && (p2 != 0xff00)) returnCode = PARAMETER_LIMIT_ERROR;
+        break;
+      }
+    }
+  }
+  return returnCode;
+}
+
+// 4. three uint16_t parameters (FC 0x16)
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint16_t p3) {
+  LOG_V("Check data #4\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FC16_TYPE && ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    } 
+  }
+  return returnCode;
+}
+
+// 5. two uint16_t parameters, a uint8_t length byte and a uint16_t* pointer to array of words (FC 0x10)
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint16_t *arrayOfWords) {
+  LOG_V("Check data #5\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FC10_TYPE && ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    } else {
+      if ((p2 == 0) || (p2 > 0x7b)) returnCode = PARAMETER_LIMIT_ERROR;
+      else if (count != (p2 * 2)) returnCode = ILLEGAL_DATA_VALUE;
+    }
+  }
+  return returnCode;
+}
+
+// 6. two uint16_t parameters, a uint8_t length byte and a uint16_t* pointer to array of bytes (FC 0x0f)
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint8_t *arrayOfBytes) {
+  LOG_V("Check data #6\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FC0F_TYPE && ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    } else {
+      if ((p2 == 0) || (p2 > 0x7b0)) returnCode = PARAMETER_LIMIT_ERROR;
+      else if (count != ((p2 / 8 + (p2 % 8 ? 1 : 0)))) returnCode = ILLEGAL_DATA_VALUE;
+    }
+  }
+  return returnCode;
+}
+
+// 7. generic constructor for preformatted data ==> count is counting bytes!
+Error ModbusMessage::checkData(uint8_t serverID, uint8_t functionCode, uint16_t count, uint8_t *arrayOfBytes) {
+  LOG_V("Check data #7\n");
+  Error returnCode = checkServerFC(serverID, functionCode);
+  if (returnCode == SUCCESS)
+  {
+    FCType ft = FCT::getType(functionCode);
+    if (ft != FCUSER && ft != FCGENERIC) {
+      returnCode = PARAMETER_COUNT_ERROR;
+    } 
+  }
+  return returnCode;
+}
+
+// Factory methods to create valid Modbus messages from the parameters
+// 1. no additional parameter (FCs 0x07, 0x0b, 0x0c, 0x11)
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(2);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode);
+  }
+  return returnCode;
+}
+
+// 2. one uint16_t parameter (FC 0x18)
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode, p1);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(4);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode, p1);
+  }
+  return returnCode;
+}
+
+// 3. two uint16_t parameters (FC 0x01, 0x02, 0x03, 0x04, 0x05, 0x06)
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode, p1, p2);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(6);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode, p1, p2);
+  }
+  return returnCode;
+}
+
+// 4. three uint16_t parameters (FC 0x16)
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint16_t p3) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode, p1, p2, p3);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(8);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode, p1, p2, p3);
+  }
+  return returnCode;
+}
+
+// 5. two uint16_t parameters, a uint8_t length byte and a uint16_t* pointer to array of words (FC 0x10)
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint16_t *arrayOfWords) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode, p1, p2, count, arrayOfWords);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(7 + count * 2);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode, p1, p2);
+    add(count);
+    for (uint8_t i = 0; i < (count >> 1); ++i) {
+      add(arrayOfWords[i]);
+    }
+  }
+  return returnCode;
+}
+
+// 6. two uint16_t parameters, a uint8_t length byte and a uint8_t* pointer to array of bytes (FC 0x0f)
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint8_t *arrayOfBytes) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode, p1, p2, count, arrayOfBytes);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(7 + count);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode, p1, p2);
+    add(count);
+    for (uint8_t i = 0; i < count; ++i) {
+      add(arrayOfBytes[i]);
+    }
+  }
+  return returnCode;
+}
+
+// 7. generic constructor for preformatted data ==> count is counting bytes!
+Error ModbusMessage::setMessage(uint8_t serverID, uint8_t functionCode, uint16_t count, uint8_t *arrayOfBytes) {
+  // Check parameter for validity
+  Error returnCode = checkData(serverID, functionCode, count, arrayOfBytes);
+  // No error? 
+  if (returnCode == SUCCESS)
+  {
+    // Yes, all fine. Create new ModbusMessage
+    MM_data.reserve(2 + count);
+    MM_data.shrink_to_fit();
+    MM_data.clear();
+    add(serverID, functionCode);
+    for (uint8_t i = 0; i < count; ++i) {
+      add(arrayOfBytes[i]);
+    }
+  }
+  return returnCode;
+}
+
+// 8. Error response generator
+Error ModbusMessage::setError(uint8_t serverID, uint8_t functionCode, Error errorCode) {
+  // No error checking for server ID or function code here, as both may be the cause for the message!? 
+  MM_data.reserve(3);
+  MM_data.shrink_to_fit();
+  MM_data.clear();
+  add(serverID, static_cast<uint8_t>((functionCode | 0x80) & 0xFF), static_cast<uint8_t>(errorCode));
+  return SUCCESS;
+}
+
+// Error output in case a message constructor will fail
+void ModbusMessage::printError(const char *file, int lineNo, Error e, uint8_t serverID, uint8_t functionCode) {
+  LOG_E("(%s, line %d) Error in constructor: %02X - %s (%02X/%02X)\n", file_name(file), lineNo, e, (const char *)(ModbusError(e)), serverID, functionCode);
+}
+
+uint8_t ModbusMessage::floatOrder[] = { 0xFF };
+uint8_t ModbusMessage::doubleOrder[] = { 0xFF };
diff --git a/lib/eModbus/src/ModbusMessage.h b/lib/eModbus/src/ModbusMessage.h
new file mode 100644
index 000000000..d343a0555
--- /dev/null
+++ b/lib/eModbus/src/ModbusMessage.h
@@ -0,0 +1,216 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_MESSAGE_H
+#define _MODBUS_MESSAGE_H
+#include "ModbusTypeDefs.h"
+#include "ModbusError.h"
+#include <type_traits>
+#include <vector>
+
+using Modbus::Error;
+using Modbus::FCType;
+using Modbus::FCT;
+using std::vector;
+
+class ModbusMessage {
+public:
+  // Default empty message Constructor - optionally takes expected size of MM_data
+  explicit ModbusMessage(uint16_t dataLen = 0);
+
+  // Special message Constructor - takes a std::vector<uint8_t>
+  explicit ModbusMessage(std::vector<uint8_t> s);
+
+  // Message constructors - internally setMessage() is called
+  // WARNING: if parameters are invalid, message will _NOT_ be set up!
+  template <typename... Args>
+  ModbusMessage(uint8_t serverID, uint8_t functionCode, Args&&... args) { // NOLINT
+    Error e = SUCCESS;
+    if ((e = setMessage(serverID, functionCode, std::forward<Args>(args) ...)) != SUCCESS) {
+      printError(__FILE__, __LINE__, e, serverID, functionCode);
+    }
+  }
+
+  // Destructor
+  ~ModbusMessage();
+
+  // Assignment operator
+  ModbusMessage& operator=(const ModbusMessage& m);
+  
+  // Copy constructor
+  ModbusMessage(const ModbusMessage& m);
+
+#ifndef NO_MOVE
+  // Move constructor
+	ModbusMessage(ModbusMessage&& m);
+  
+	// Move assignment
+	ModbusMessage& operator=(ModbusMessage&& m);
+#endif
+
+  // Comparison operators
+  bool operator==(const ModbusMessage& m);
+  bool operator!=(const ModbusMessage& m);
+  operator bool();
+  
+  // Exposed methods of std::vector
+  const uint8_t   *data();  // address of MM_data
+  uint16_t   size();  // used length in MM_data
+  uint8_t    operator[](uint16_t index) const; // provide restricted operator[] interface
+  void push_back(const uint8_t& val); // add a byte at the end of MM_data
+  void clear();             // delete message contents
+  uint16_t resize(uint16_t newSize);  // resize MM_data
+
+  // provide iterator interface on MM_data
+  typedef std::vector<uint8_t>::const_iterator const_iterator;
+  const_iterator begin() const { return MM_data.begin(); }
+  const_iterator end() const   { return MM_data.end(); }
+
+  // Add append() for two ModbusMessages or a std::vector<uint8_t> to be appended
+  void append(ModbusMessage& m);
+  void append(std::vector<uint8_t>& m);
+
+  // Modbus data extraction
+  uint8_t getServerID() const;      // returns Server ID or 0 if MM_data is shorter than 3
+  uint8_t getFunctionCode() const;  // returns FC or 0 if MM_data is shorter than 3
+  Error   getError() const;         // getError() - returns error code (MM_data[2], if MM_data[1] > 0x7F, else SUCCESS)
+
+  // Modbus data manipulation
+  void    setServerID(uint8_t serverID); // Change server ID
+  void    setFunctionCode(uint8_t FC);   // Change function code
+
+  // add() variant to copy a buffer into MM_data. Returns updated size
+  uint16_t add(const uint8_t *arrayOfBytes, uint16_t count);
+
+  // add() - add a single data element MSB first to MM_data. Returns updated size
+  template <class T> uint16_t add(T v) {
+    uint16_t sz = sizeof(T);    // Size of value to be added
+
+    // Copy it MSB first
+    while (sz) {
+      sz--;
+      MM_data.push_back((v >> (sz << 3)) & 0xFF);
+    }
+    // Return updated size (logical length of message so far)
+    return MM_data.size();
+  }
+
+  // Template function to extend add(A) to add(A, B, C, ...)
+  template <class T, class... Args> 
+  typename std::enable_if<!std::is_pointer<T>::value, uint16_t>::type
+  add(T v, Args... args) {
+      add(v);
+      return add(args...);
+  }
+
+// get() - read a byte array of a given size into a vector<uint8_t>. Returns updated index
+uint16_t get(uint16_t index, vector<uint8_t>& v, uint8_t count) const;
+
+// get() - recursion stopper for template function below
+inline uint16_t get(uint16_t index) const { return index; }
+
+// Template function to extend getOne(index, A&) to get(index, A&, B&, C&, ...)
+template <class T, class... Args>
+typename std::enable_if<!std::is_pointer<T>::value, uint16_t>::type
+get(uint16_t index, T& v, Args&... args) const {
+  uint16_t pos = getOne(index, v);
+  return get(pos, args...);
+}
+
+// add() variant for vectors of uint8_t
+uint16_t add(vector<uint8_t> v);
+
+// add() variants for float and double values
+uint16_t add(float v, int swapRules = 0);
+uint16_t add(double v, int swapRules = 0);
+
+// get() variants for float and double values
+uint16_t get(uint16_t index, float& v, int swapRules = 0) const;
+uint16_t get(uint16_t index, double& v, int swapRules = 0) const;
+
+  // Message generation methods
+  // 1. no additional parameter (FCs 0x07, 0x0b, 0x0c, 0x11)
+  Error setMessage(uint8_t serverID, uint8_t functionCode);
+
+  // 2. one uint16_t parameter (FC 0x18)
+  Error setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1);
+  
+  // 3. two uint16_t parameters (FC 0x01, 0x02, 0x03, 0x04, 0x05, 0x06)
+  Error setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2);
+  
+  // 4. three uint16_t parameters (FC 0x16)
+  Error setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint16_t p3);
+  
+  // 5. two uint16_t parameters, a uint8_t length byte and a uint8_t* pointer to array of words (FC 0x10)
+  Error setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint16_t *arrayOfWords);
+  
+  // 6. two uint16_t parameters, a uint8_t length byte and a uint16_t* pointer to array of bytes (FC 0x0f)
+  Error setMessage(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint8_t *arrayOfBytes);
+
+  // 7. generic constructor for preformatted data ==> count is counting bytes!
+  Error setMessage(uint8_t serverID, uint8_t functionCode, uint16_t count, uint8_t *arrayOfBytes);
+
+  // 8. error response
+  Error setError(uint8_t serverID, uint8_t functionCode, Error errorCode);
+  
+protected:
+  // Data validation methods - used by the above!
+  // 0. serverID and function code - used by all of the below
+  static Error checkServerFC(uint8_t serverID, uint8_t functionCode);
+
+  // 1. no additional parameter (FCs 0x07, 0x0b, 0x0c, 0x11)
+  static Error checkData(uint8_t serverID, uint8_t functionCode);
+  
+  // 2. one uint16_t parameter (FC 0x18)
+  static Error checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1);
+  
+  // 3. two uint16_t parameters (FC 0x01, 0x02, 0x03, 0x04, 0x05, 0x06)
+  static Error checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2);
+  
+  // 4. three uint16_t parameters (FC 0x16)
+  static Error checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint16_t p3);
+  
+  // 5. two uint16_t parameters, a uint8_t length byte and a uint8_t* pointer to array of words (FC 0x10)
+  static Error checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint16_t *arrayOfWords);
+  
+  // 6. two uint16_t parameters, a uint8_t length byte and a uint16_t* pointer to array of bytes (FC 0x0f)
+  static Error checkData(uint8_t serverID, uint8_t functionCode, uint16_t p1, uint16_t p2, uint8_t count, uint8_t *arrayOfBytes);
+
+  // 7. generic constructor for preformatted data ==> count is counting bytes!
+  static Error checkData(uint8_t serverID, uint8_t functionCode, uint16_t count, uint8_t *arrayOfBytes);
+
+  // Error output in case a message constructor will fail
+  static void printError(const char *file, int lineNo, Error e, uint8_t serverID, uint8_t functionCode);
+
+  std::vector<uint8_t> MM_data;  // Message data buffer
+
+  static uint8_t floatOrder[sizeof(float)]; // order of bytes in a float variable
+  static uint8_t doubleOrder[sizeof(double)]; // order of bytes in a double variable
+
+  static uint8_t determineFloatOrder();
+  static uint8_t determineDoubleOrder();
+
+  static float swapFloat(float& f, int swapRule);
+  static double swapDouble(double& f, int swapRule);
+
+  // getOne() - read a MSB-first value starting at byte index. Returns updated index
+  template <typename T> uint16_t getOne(uint16_t index, T& retval) const {
+    uint16_t sz = sizeof(retval);    // Size of value to be read
+
+    retval = 0;                      // return value
+
+    // Will it fit?
+    if (index <= MM_data.size() - sz) {
+      // Yes. Copy it MSB first
+      while (sz) {
+        sz--;
+        retval <<= 8;
+        retval |= MM_data[index++];
+      }
+    }
+    return index;
+  }
+};
+
+#endif
diff --git a/lib/eModbus/src/ModbusServer.cpp b/lib/eModbus/src/ModbusServer.cpp
new file mode 100644
index 000000000..21ada8334
--- /dev/null
+++ b/lib/eModbus/src/ModbusServer.cpp
@@ -0,0 +1,175 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include <Arduino.h>
+#include "ModbusServer.h"
+
+#undef LOCAL_LOG_LEVEL
+// #define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+#include "Logging.h"
+
+// registerWorker: register a worker function for a certain serverID/FC combination
+// If there is one already, it will be overwritten!
+void ModbusServer::registerWorker(uint8_t serverID, uint8_t functionCode, MBSworker worker) {
+  workerMap[serverID][functionCode] = worker;
+  LOG_D("Registered worker for %02X/%02X\n", serverID, functionCode);
+}
+
+// getWorker: if a worker function is registered, return its address, nullptr otherwise
+MBSworker ModbusServer::getWorker(uint8_t serverID, uint8_t functionCode) {
+  // Search the FC map associated with the serverID
+  auto svmap = workerMap.find(serverID);
+  // Is there one?
+  if (svmap != workerMap.end()) {
+    // Yes. Now look for the function code in the inner map
+    auto fcmap = svmap->second.find(functionCode);;
+    // Found it?
+    if (fcmap != svmap->second.end()) {
+      // Yes. Return the function pointer for it.
+      LOG_D("Worker found for %02X/%02X\n", serverID, functionCode);
+      return fcmap->second;
+      // No, no explicit worker found, but may be there is one for ANY_FUNCTION_CODE?
+    } else {
+      fcmap = svmap->second.find(ANY_FUNCTION_CODE);;
+      // Found it?
+      if (fcmap != svmap->second.end()) {
+        // Yes. Return the function pointer for it.
+        LOG_D("Worker found for %02X/ANY\n", serverID);
+        return fcmap->second;
+      }
+    }
+  }
+  // No matching function pointer found
+  LOG_D("No matching worker found\n");
+  return nullptr;
+}
+
+// unregisterWorker; remove again all or part of the registered workers for a given server ID
+// Returns true if the worker was found and removed
+bool ModbusServer::unregisterWorker(uint8_t serverID, uint8_t functionCode) {
+  uint16_t numEntries = 0;    // Number of entries removed
+
+  // Is there at least one entry for the serverID?
+  auto svmap = workerMap.find(serverID);
+  // Is there one?
+  if (svmap != workerMap.end()) {
+    // Yes. we may proceed with it
+    // Are we to look for a single serverID/FC combination?
+    if (functionCode) {
+      // Yes. 
+      numEntries = svmap->second.erase(functionCode);
+    } else {
+      // No, the serverID shall be removed with all references
+      numEntries = workerMap.erase(serverID);
+    }
+  } 
+  LOG_D("Removed %d worker entries for %d/%d\n", numEntries, serverID, functionCode);
+  return (numEntries ? true : false);
+}
+
+// isServerFor: if any worker function is registered for the given serverID, return true
+bool ModbusServer::isServerFor(uint8_t serverID) {
+  // Search the FC map for the serverID
+  auto svmap = workerMap.find(serverID);
+  // Is it there? Then return true
+  if (svmap != workerMap.end()) return true;
+  // No, serverID was not found. Return false
+  return false;
+}
+
+// getMessageCount: read number of messages processed
+uint32_t ModbusServer::getMessageCount() { 
+  return messageCount;
+}
+
+// getErrorCount: read number of errors responded
+uint32_t ModbusServer::getErrorCount() { 
+  return errorCount;
+}
+
+// resetCounts: set both message and error counts to zero
+void ModbusServer::resetCounts() {
+  {
+    LOCK_GUARD(cntLock, m);
+    messageCount = 0;
+    errorCount = 0;
+  }
+}
+
+// LocalRequest: get response from locally running server.
+ModbusMessage ModbusServer::localRequest(ModbusMessage msg) {
+  ModbusMessage m;
+  uint8_t serverID = msg.getServerID();
+  uint8_t functionCode = msg.getFunctionCode();
+  LOG_D("Local request for %02X/%02X\n", serverID, functionCode);
+  HEXDUMP_V("Request", msg.data(), msg.size());
+  messageCount++;
+  // Try to get a worker for the request
+  MBSworker worker = getWorker(serverID, functionCode);
+  // Did we get one?
+  if (worker != nullptr) {
+    // Yes. call it and return the response
+    LOG_D("Call worker\n");
+    m = worker(msg);
+    LOG_D("Worker responded\n");
+    HEXDUMP_V("Worker response", m.data(), m.size());
+    // Process Response. Is it one of the predefined types?
+    if (m[0] == 0xFF && (m[1] == 0xF0 || m[1] == 0xF1)) {
+      // Yes. Check it
+      switch (m[1]) {
+      case 0xF0: // NIL
+        m.clear();
+        break;
+      case 0xF1: // ECHO
+        m.clear();
+        m.append(msg);
+        break;
+      default:   // Will not get here, but lint likes it!
+        break;
+      }
+    }
+    HEXDUMP_V("Response", m.data(), m.size());
+    if (m.getError() != SUCCESS) {
+      errorCount++;
+    }
+    return m;
+  } else {
+    LOG_D("No worker found. Error response.\n");
+    // No. Is there at least one worker for the serverID?
+    if (isServerFor(serverID)) {
+      // Yes. Respond with "illegal function code"
+      m.setError(serverID, functionCode, ILLEGAL_FUNCTION);
+    } else {
+      // No. Respond with "Invalid server ID"
+      m.setError(serverID, functionCode, INVALID_SERVER);
+    }
+    errorCount++;
+    return m;
+  }
+  // We should never get here...
+  LOG_C("Internal problem: should not get here!\n");
+  m.setError(serverID, functionCode, UNDEFINED_ERROR);
+  errorCount++;
+  return m;
+}
+
+// Constructor
+ModbusServer::ModbusServer() :
+  messageCount(0),
+  errorCount(0) { }
+
+// Destructor
+ModbusServer::~ModbusServer() {
+}
+
+// listServer: Print out all mapped server/FC combinations
+void ModbusServer::listServer() {
+  for (auto it = workerMap.begin(); it != workerMap.end(); ++it) {
+    LOG_N("Server %3d: ", it->first);
+    for (auto it2 = it->second.begin(); it2 != it->second.end(); it2++) {
+      LOGRAW_N(" %02X", it2->first);
+    }
+    LOGRAW_N("\n");
+  }
+}
diff --git a/lib/eModbus/src/ModbusServer.h b/lib/eModbus/src/ModbusServer.h
new file mode 100644
index 000000000..bdc4e90f2
--- /dev/null
+++ b/lib/eModbus/src/ModbusServer.h
@@ -0,0 +1,86 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_SERVER_H
+#define _MODBUS_SERVER_H
+
+#include "options.h"
+
+#include <map>
+#include <vector>
+#include <functional>
+#if USE_MUTEX
+#include <mutex>      // NOLINT
+#endif
+#include "ModbusTypeDefs.h"
+#include "ModbusError.h"
+#include "ModbusMessage.h"
+
+#if USE_MUTEX
+using std::mutex;
+using std::lock_guard;
+#endif
+
+// Standard response variants for "no response" and "echo the request"
+const ModbusMessage NIL_RESPONSE (std::vector<uint8_t>{0xFF, 0xF0});
+const ModbusMessage ECHO_RESPONSE(std::vector<uint8_t>{0xFF, 0xF1});
+
+// MBSworker: function signature for worker functions to handle single serverID/functionCode combinations
+using MBSworker = std::function<ModbusMessage(ModbusMessage msg)>;
+
+class ModbusServer {
+public:
+  // registerWorker: register a worker function for a certain serverID/FC combination
+  // If there is one already, it will be overwritten!
+  void registerWorker(uint8_t serverID, uint8_t functionCode, MBSworker worker);
+  
+  // getWorker: if a worker function is registered, return its address, nullptr otherwise
+  MBSworker getWorker(uint8_t serverID, uint8_t functionCode);
+
+  // unregisterWorker; remove again all or part of the registered workers for a given server ID
+  // Returns true if the worker was found and removed
+  bool unregisterWorker(uint8_t serverID, uint8_t functionCode = 0);
+
+  // isServerFor: if any worker function is registered for the given serverID, return true
+  bool isServerFor(uint8_t serverID);
+
+  // getMessageCount: read number of messages processed
+  uint32_t getMessageCount();
+
+  // getErrorCount: read number of errors responded
+  uint32_t getErrorCount();
+
+  // resetCounts: set both message and error counts to zero
+  void resetCounts();
+
+  // Local request to the server
+  ModbusMessage localRequest(ModbusMessage msg);
+
+  // listServer: print out all server/FC combinations served
+  void listServer();
+
+protected:
+  // Constructor
+  ModbusServer();
+
+  // Destructor
+  ~ModbusServer();
+
+  // Prevent copy construction or assignment
+  ModbusServer(ModbusServer& other) = delete;
+  ModbusServer& operator=(ModbusServer& other) = delete;
+
+  // Virtual function to prevent this class being instantiated
+  virtual void isInstance() = 0;
+
+  std::map<uint8_t, std::map<uint8_t, MBSworker>> workerMap;      // map on serverID->functionCode->worker function
+  uint32_t messageCount;         // Number of Requests processed
+  uint32_t errorCount;           // Number of errors responded
+  #if USE_MUTEX
+  mutex m;                       // mutex to cover changes to messageCount and errorCount
+  #endif
+};
+
+
+#endif
diff --git a/lib/eModbus/src/ModbusServerEthernet.h b/lib/eModbus/src/ModbusServerEthernet.h
new file mode 100644
index 000000000..b1f9ceba1
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerEthernet.h
@@ -0,0 +1,19 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_SERVER_ETHERNET_H
+#define _MODBUS_SERVER_ETHERNET_H
+#include "options.h"
+#if HAS_ETHERNET == 1
+#include <Ethernet.h>
+#include <SPI.h>
+
+#undef SERVER_END
+#define SERVER_END // NIL for Ethernet
+
+#include "ModbusServerTCPtemp.h"
+using ModbusServerEthernet = ModbusServerTCP<EthernetServer, EthernetClient>;
+#endif
+
+#endif
diff --git a/lib/eModbus/src/ModbusServerRTU.cpp b/lib/eModbus/src/ModbusServerRTU.cpp
new file mode 100644
index 000000000..5a70e675a
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerRTU.cpp
@@ -0,0 +1,260 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusServerRTU.h"
+
+#if HAS_FREERTOS
+
+#undef LOG_LEVEL_LOCAL
+#include "Logging.h"
+
+// Init number of created ModbusServerRTU objects
+uint8_t ModbusServerRTU::instanceCounter = 0;
+
+// Constructor with RTS pin GPIO (or -1)
+ModbusServerRTU::ModbusServerRTU(uint32_t timeout, int rtsPin) :
+  ModbusServer(),
+  serverTask(nullptr),
+  serverTimeout(timeout),
+  MSRserial(nullptr),
+  MSRinterval(2000),     // will be calculated in begin()!
+  MSRlastMicros(0),
+  MSRrtsPin(rtsPin), 
+  MSRuseASCII(false),
+  MSRskipLeadingZeroByte(false),
+  listener(nullptr),
+  sniffer(nullptr) {
+  // Count instances one up
+  instanceCounter++;
+  // If we have a GPIO RE/DE pin, configure it.
+  if (MSRrtsPin >= 0) {
+    pinMode(MSRrtsPin, OUTPUT);
+    MRTSrts = [this](bool level) {
+      digitalWrite(MSRrtsPin, level);
+    };
+    MRTSrts(LOW);
+  } else {
+    MRTSrts = RTUutils::RTSauto;
+  }
+}
+
+// Constructor with RTS callback
+ModbusServerRTU::ModbusServerRTU(uint32_t timeout, RTScallback rts) :
+  ModbusServer(),
+  serverTask(nullptr),
+  serverTimeout(timeout),
+  MSRserial(nullptr),
+  MSRinterval(2000),     // will be calculated in begin()!
+  MSRlastMicros(0),
+  MRTSrts(rts), 
+  MSRuseASCII(false),
+  MSRskipLeadingZeroByte(false),
+  listener(nullptr),
+  sniffer(nullptr) {
+  // Count instances one up
+  instanceCounter++;
+  // Configure RTS callback
+  MSRrtsPin = -1;
+  MRTSrts(LOW);
+}
+
+// Destructor
+ModbusServerRTU::~ModbusServerRTU() {
+}
+
+// start: create task with RTU server - general version
+void ModbusServerRTU::begin(Stream& serial, uint32_t baudRate, int coreID) {
+  MSRserial = &serial;
+  doBegin(baudRate, coreID);
+}
+
+// start: create task with RTU server - HardwareSerial versions
+void ModbusServerRTU::begin(HardwareSerial& serial, int coreID) {
+  MSRserial = &serial;
+  uint32_t baudRate = serial.baudRate();
+  serial.setRxFIFOFull(1);
+  doBegin(baudRate, coreID);
+}
+
+void ModbusServerRTU::doBegin(uint32_t baudRate, int coreID) {
+  // Task already running? Stop it in case.
+  end();
+
+  // Set minimum interval time
+  MSRinterval = RTUutils::calculateInterval(baudRate);
+
+  // Create unique task name
+  char taskName[18];
+  snprintf(taskName, 18, "MBsrv%02XRTU", instanceCounter);
+
+  // Start task to handle the client
+  xTaskCreatePinnedToCore((TaskFunction_t)&serve, taskName, SERVER_TASK_STACK, this, 8, &serverTask, coreID >= 0 ? coreID : NULL);
+
+  LOG_D("Server task %d started. Interval=%d\n", (uint32_t)serverTask, MSRinterval);
+}
+
+// end: kill server task
+void ModbusServerRTU::end() {
+  if (serverTask != nullptr) {
+    vTaskDelete(serverTask);
+    LOG_D("Server task %d stopped.\n", (uint32_t)serverTask);
+    serverTask = nullptr;
+  }
+}
+
+// Toggle protocol to ModbusASCII
+void ModbusServerRTU::useModbusASCII(unsigned long timeout) {
+  MSRuseASCII = true;
+  serverTimeout = timeout; // Set timeout to ASCII's value
+  LOG_D("Protocol mode: ASCII\n");
+}
+
+// Toggle protocol to ModbusRTU
+void ModbusServerRTU::useModbusRTU() {
+  MSRuseASCII = false;
+  LOG_D("Protocol mode: RTU\n");
+}
+
+// Inquire protocol mode
+bool ModbusServerRTU::isModbusASCII() {
+  return MSRuseASCII;
+}
+
+// Toggle skipping of leading 0x00 byte
+void ModbusServerRTU::skipLeading0x00(bool onOff) {
+  MSRskipLeadingZeroByte = onOff;
+  LOG_D("Skip leading 0x00 mode = %s\n", onOff ? "ON" : "OFF");
+}
+
+// Special case: worker to react on broadcast requests
+void ModbusServerRTU::registerBroadcastWorker(MSRlistener worker) {
+  // If there is one already, it will be overwritten!
+  listener = worker;
+  LOG_D("Registered worker for broadcast requests\n");
+}
+
+// Even more special: register a sniffer worker
+void ModbusServerRTU::registerSniffer(MSRlistener worker) {
+  // If there is one already, it will be overwritten!
+  // This holds true for the broadcast worker as well, 
+  // so a sniffer never will do else but to sniff on broadcast requests!
+  sniffer = worker;
+  LOG_D("Registered sniffer\n");
+}
+
+// serve: loop until killed and receive messages from the RTU interface
+void ModbusServerRTU::serve(ModbusServerRTU *myServer) {
+  ModbusMessage request;                // received request message
+  ModbusMessage m;                      // Application's response data
+  ModbusMessage response;               // Response proper to be sent
+
+  // init microseconds timer
+  myServer->MSRlastMicros = micros();
+
+  while (true) {
+    // Initialize all temporary vectors
+    request.clear();
+    response.clear();
+    m.clear();
+
+    // Wait for and read an request
+    request = RTUutils::receive(
+      'S',
+      *(myServer->MSRserial), 
+      myServer->serverTimeout, 
+      myServer->MSRlastMicros, 
+      myServer->MSRinterval, 
+      myServer->MSRuseASCII, 
+      myServer->MSRskipLeadingZeroByte);
+
+    // Request longer than 1 byte (that will signal an error in receive())? 
+    if (request.size() > 1) {
+      LOG_D("Request received.\n");
+
+      // Yes. 
+      // Do we have a sniffer listening?
+      if (myServer->sniffer) {
+        // Yes. call it
+        myServer->sniffer(request);
+      }
+      // Is it a broadcast?
+      if (request[0] == 0) {
+        // Yes. Do we have a listener?
+        if (myServer->listener) {
+          // Yes. call it
+          myServer->listener(request);
+        }
+        // else we simply ignore it
+      } else {
+        // No Broadcast. 
+        // Do we have a callback function registered for it?
+        MBSworker callBack = myServer->getWorker(request[0], request[1]);
+        if (callBack) {
+          LOG_D("Callback found.\n");
+          // Yes, we do. Count the message
+          {
+            LOCK_GUARD(cntLock, myServer->m);
+            myServer->messageCount++;
+          }
+          // Get the user's response
+          LOG_D("Callback called.\n");
+          m = callBack(request);
+          HEXDUMP_V("Callback response", m.data(), m.size());
+
+          // Process Response. Is it one of the predefined types?
+          if (m[0] == 0xFF && (m[1] == 0xF0 || m[1] == 0xF1)) {
+            // Yes. Check it
+            switch (m[1]) {
+            case 0xF0: // NIL
+              response.clear();
+              break;
+            case 0xF1: // ECHO
+              response = request;
+              if (request.getFunctionCode() == WRITE_MULT_REGISTERS ||
+                  request.getFunctionCode() == WRITE_MULT_COILS) {
+                response.resize(6);
+              }
+              break;
+            default:   // Will not get here, but lint likes it!
+              break;
+            }
+          } else {
+            // No predefined. User provided data in free format
+            response = m;
+          }
+        } else {
+          // No callback. Is at least the serverID valid and no broadcast?
+          if (myServer->isServerFor(request[0]) && request[0] != 0x00) {
+            // Yes. Send back a ILLEGAL_FUNCTION error
+            response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_FUNCTION);
+          }
+          // Else we will ignore the request, as it is not meant for us and we do not deal with broadcasts!
+        }
+        // Do we have gathered a valid response now?
+        if (response.size() >= 3) {
+          // Yes. send it back.
+          RTUutils::send(*(myServer->MSRserial), myServer->MSRlastMicros, myServer->MSRinterval, myServer->MRTSrts, response, myServer->MSRuseASCII);
+          LOG_D("Response sent.\n");
+          // Count it, in case we had an error response
+          if (response.getError() != SUCCESS) {
+            LOCK_GUARD(errorCntLock, myServer->m);
+            myServer->errorCount++;
+          }
+        }
+      }
+    } else {
+      // No, we got a 1-byte request, meaning an error has happened in receive()
+      // This is a server, so we will ignore TIMEOUT.
+      if (request[0] != TIMEOUT) {
+        // Any other error could be important for debugging, so print it
+        ModbusError me((Error)request[0]);
+        LOG_E("RTU receive: %02X - %s\n", (int)me, (const char *)me);
+      }
+    }
+    // Give scheduler room to breathe
+    delay(1);
+  }
+}
+
+#endif
diff --git a/lib/eModbus/src/ModbusServerRTU.h b/lib/eModbus/src/ModbusServerRTU.h
new file mode 100644
index 000000000..c4c601512
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerRTU.h
@@ -0,0 +1,92 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_SERVER_RTU_H
+#define _MODBUS_SERVER_RTU_H
+
+#include "options.h"
+
+#if HAS_FREERTOS
+
+#include <Arduino.h>
+#include "Stream.h"
+#include "ModbusServer.h"
+#include "RTUutils.h"
+
+extern "C" {
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+}
+
+// Specal function signature for broadcast or sniffer listeners
+using MSRlistener = std::function<void(ModbusMessage msg)>;
+
+class ModbusServerRTU : public ModbusServer {
+public:
+  // Constructors
+  explicit ModbusServerRTU(uint32_t timeout, int rtsPin = -1);
+  ModbusServerRTU(uint32_t timeout, RTScallback rts);
+
+  // Destructor
+  ~ModbusServerRTU();
+
+  // begin: create task with RTU server to accept requests
+  void begin(Stream& serial, uint32_t baudRate, int coreID = -1);
+  void begin(HardwareSerial& serial, int coreID = -1);
+
+  // end: kill server task
+  void end();
+
+  // Toggle protocol to ModbusASCII
+  void useModbusASCII(unsigned long timeout = 1000);
+
+  // Toggle protocol to ModbusRTU
+  void useModbusRTU();
+
+  // Inquire protocol mode
+  bool isModbusASCII();
+
+  // Toggle skipping of leading 0x00 byte
+  void skipLeading0x00(bool onOff = true);
+
+  // Special case: worker to react on broadcast requests
+  void registerBroadcastWorker(MSRlistener worker);
+
+  // Even more special: register a sniffer worker
+  void registerSniffer(MSRlistener worker);
+
+protected:
+  // Prevent copy construction and assignment
+  ModbusServerRTU(ModbusServerRTU& m) = delete;
+  ModbusServerRTU& operator=(ModbusServerRTU& m) = delete;
+
+  inline void isInstance() { }           // Make class instantiable
+
+  // internal common begin function
+  void doBegin(uint32_t baudRate, int coreID);
+
+  static uint8_t instanceCounter;        // Number of RTU servers created (for task names)
+  TaskHandle_t serverTask;               // task of the started server
+  uint32_t serverTimeout;                // given timeout for receive. Does not really
+                                         // matter for a server, but is needed in 
+                                         // RTUutils. After timeout without any message
+                                         // the server will pause ~1ms and start 
+                                         // receive again.
+  Stream *MSRserial;                     // The serial interface to use
+  uint32_t MSRinterval;                  // Bus quiet time between messages
+  unsigned long MSRlastMicros;           // microsecond time stamp of last bus activity
+  int8_t MSRrtsPin;                      // GPIO number of the RS485 module's RE/DE line
+  RTScallback MRTSrts;                   // Callback to set the RTS line to HIGH/LOW
+  bool MSRuseASCII;                      // true=ModbusASCII, false=ModbusRTU
+  bool MSRskipLeadingZeroByte;           // true=first byte ignored if 0x00, false=all bytes accepted
+  MSRlistener listener;                  // Broadcast listener 
+  MSRlistener sniffer;                   // Sniffer listener 
+
+  // serve: loop function for server task
+  static void serve(ModbusServerRTU *myself);
+};
+
+#endif  // HAS_FREERTOS
+
+#endif // INCLUDE GUARD
diff --git a/lib/eModbus/src/ModbusServerTCPasync.cpp b/lib/eModbus/src/ModbusServerTCPasync.cpp
new file mode 100644
index 000000000..3f869a36a
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerTCPasync.cpp
@@ -0,0 +1,267 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+
+#include "ModbusServerTCPasync.h"
+#define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+// #undef LOCAL_LOG_LEVEL
+#include "Logging.h"
+
+ModbusServerTCPasync::mb_client::mb_client(ModbusServerTCPasync * s, AsyncClient * c)
+    : server(s)
+    , client(c)
+    , lastActiveTime(millis())
+    , message(nullptr)
+    , error(SUCCESS)
+    , outbox() {
+    client->onData([](void * i, AsyncClient * c, void * data, size_t len) { (static_cast<mb_client *>(i))->onData(static_cast<uint8_t *>(data), len); }, this);
+    client->onPoll([](void * i, AsyncClient * c) { (static_cast<mb_client *>(i))->onPoll(); }, this);
+    client->onDisconnect([](void * i, AsyncClient * c) { (static_cast<mb_client *>(i))->onDisconnect(); }, this);
+    client->setNoDelay(true);
+}
+
+ModbusServerTCPasync::mb_client::~mb_client() {
+    // clear outbox, if data is left
+    while (!outbox.empty()) {
+        outbox.pop();
+    }
+
+    delete client; // will also close connection, if any
+}
+
+void ModbusServerTCPasync::mb_client::onData(uint8_t * data, size_t len) {
+    lastActiveTime = millis();
+    LOG_D("data len %d\n", len);
+
+    Error  error = SUCCESS;
+    size_t i     = 0;
+    while (i < len) {
+        // 0. start
+        if (!message) {
+            message = new ModbusMessage(8);
+            error   = SUCCESS;
+        }
+
+        //  1. get minimal 8 bytes to move on
+        while (message->size() < 8 && i < len) {
+            message->push_back(data[i++]);
+        }
+
+        // 2. preliminary validation: protocol bytes and message length
+        if ((*message)[2] != 0 || (*message)[3] != 0) {
+            error = TCP_HEAD_MISMATCH;
+            LOG_D("invalid protocol\n");
+        }
+        size_t messageLength = (((*message)[4] << 8) | (*message)[5]) + 6;
+        if (messageLength > 262) { // 256 + MBAP(6) = 262
+            error = PACKET_LENGTH_ERROR;
+            LOG_D("max length error\n");
+        }
+        if (error != SUCCESS) {
+            ModbusMessage response;
+            response.setError(message->getServerID(), message->getFunctionCode(), error);
+            message->resize(4);
+            message->add(static_cast<uint16_t>(3));
+            message->append(response);
+            addResponseToOutbox(message); // outbox has pointer ownership now
+            // reset to starting values and process remaining data
+            message = nullptr;
+            return; // protocol validation, abort further parsing
+        }
+
+        // 3. receive until request is complete
+        while (message->size() < messageLength && i < len) {
+            message->push_back(data[i++]);
+        }
+        if (message->size() == messageLength) {
+            LOG_D("request complete (len:%d)\n", message->size());
+        } else {
+            LOG_D("request incomplete (len:%d), waiting for next TCP packet\n", message->size());
+            continue;
+        }
+
+        // 4. request complete, process
+        ModbusMessage request(messageLength - 6); // create request without MBAP, with server ID
+        request.add(message->data() + 6, message->size() - 6);
+        ModbusMessage userData;
+        if (server->isServerFor(request.getServerID())) {
+            MBSworker callback = server->getWorker(request.getServerID(), request.getFunctionCode());
+            if (callback) {
+                // request is well formed and is being served by user API
+                userData = callback(request);
+                // Process Response
+                // One of the predefined types?
+                if (userData[0] == 0xFF && (userData[1] == 0xF0 || userData[1] == 0xF1)) {
+                    // Yes. Check it
+                    switch (userData[1]) {
+                    case 0xF0: // NIL
+                        userData.clear();
+                        LOG_D("NIL response\n");
+                        break;
+                    case 0xF1: // ECHO
+                        userData = request;
+                        if (request.getFunctionCode() == WRITE_MULT_REGISTERS || request.getFunctionCode() == WRITE_MULT_COILS) {
+                            userData.resize(6);
+                        }
+                        LOG_D("ECHO response\n");
+                        break;
+                    default: // Will not get here!
+                        break;
+                    }
+                } else {
+                    // No. User provided data response
+                    LOG_D("Data response\n");
+                }
+                error = SUCCESS;
+            } else { // no worker found
+                error = ILLEGAL_FUNCTION;
+            }
+        } else { // mismatch server ID
+            error = INVALID_SERVER;
+        }
+        if (error != SUCCESS) {
+            userData.setError(request.getServerID(), request.getFunctionCode(), error);
+        }
+        // Keep transaction id and protocol id
+        message->resize(4);
+        // Add new payload length
+        message->add(static_cast<uint16_t>(userData.size()));
+        // Append payload
+        message->append(userData);
+        // Transfer message data to outbox
+        addResponseToOutbox(message);
+        message = nullptr;
+    } // end while loop iterating incoming data
+}
+
+void ModbusServerTCPasync::mb_client::onPoll() {
+    LOCK_GUARD(lock1, obLock);
+    handleOutbox();
+    if (server->idle_timeout > 0 && millis() - lastActiveTime > server->idle_timeout) {
+        LOG_D("client idle, closing\n");
+        client->close();
+    }
+}
+
+void ModbusServerTCPasync::mb_client::onDisconnect() {
+    LOG_D("client disconnected\n");
+    server->onClientDisconnect(this);
+}
+
+void ModbusServerTCPasync::mb_client::addResponseToOutbox(ModbusMessage * response) {
+    if (response->size() > 0) {
+        LOCK_GUARD(lock1, obLock);
+        outbox.push(response);
+        handleOutbox();
+    }
+}
+
+void ModbusServerTCPasync::mb_client::handleOutbox() {
+    while (!outbox.empty()) {
+        ModbusMessage * m = outbox.front();
+        if (m->size() <= client->space()) {
+            LOG_D("sending (%d)\n", m->size());
+            client->add(reinterpret_cast<const char *>(m->data()), m->size(), ASYNC_WRITE_FLAG_COPY);
+            client->send();
+            delete m;
+            outbox.pop();
+        } else {
+            return;
+        }
+    }
+}
+
+ModbusServerTCPasync::ModbusServerTCPasync()
+    : server(nullptr)
+    , clients()
+    , maxNoClients(5)
+    , idle_timeout(60000) {
+    // setup will be done in 'start'
+}
+
+
+ModbusServerTCPasync::~ModbusServerTCPasync() {
+    stop();
+    delete server;
+}
+
+
+uint16_t ModbusServerTCPasync::activeClients() {
+    LOCK_GUARD(lock1, cListLock);
+    return clients.size();
+}
+
+
+bool ModbusServerTCPasync::start(uint16_t port, uint8_t max_clients, uint32_t timeout, int coreID) {
+    // don't restart if already running
+    if (server) {
+        LOG_W("Server already running.\n");
+        return false;
+    }
+
+    maxNoClients = max_clients;
+    idle_timeout = timeout;
+    server       = new AsyncServer(port);
+    if (server) {
+        server->setNoDelay(true);
+        server->onClient([](void * i, AsyncClient * c) { (static_cast<ModbusServerTCPasync *>(i))->onClientConnect(c); }, this);
+        server->begin();
+        LOG_D("Modbus server started\n");
+        return true;
+    }
+    LOG_E("Could not start server\n");
+    return false;
+}
+
+bool ModbusServerTCPasync::stop() {
+    if (!server) {
+        LOG_W("Server not running.\n");
+        return false;
+    }
+
+    // stop server to prevent new clients connecting
+    server->end();
+
+    // now close existing clients
+    LOCK_GUARD(lock1, cListLock);
+    while (!clients.empty()) {
+        // prevent onDisconnect handler to be called, resulting in deadlock
+        clients.front()->client->onDisconnect(nullptr, nullptr);
+        delete clients.front();
+        clients.pop_front();
+    }
+    delete server;
+    server = nullptr;
+    LOG_D("Modbus server stopped\n");
+    return true;
+}
+
+bool ModbusServerTCPasync::isRunning() {
+    if (server)
+        return true;
+    else
+        return false;
+}
+
+void ModbusServerTCPasync::onClientConnect(AsyncClient * client) {
+    LOG_D("new client\n");
+    LOCK_GUARD(lock1, cListLock);
+    if (clients.size() < maxNoClients) {
+        clients.emplace_back(new mb_client(this, client));
+        LOG_D("nr clients: %d\n", clients.size());
+    } else {
+        LOG_D("max number of clients reached, closing new\n");
+        client->close(true);
+        delete client;
+    }
+}
+
+void ModbusServerTCPasync::onClientDisconnect(mb_client * client) {
+    LOCK_GUARD(lock1, cListLock);
+    // delete mb_client from list
+    clients.remove_if([client](mb_client * i) { return i->client == client->client; });
+    // delete client itself
+    delete client;
+    LOG_D("nr clients: %d\n", clients.size());
+}
diff --git a/lib/eModbus/src/ModbusServerTCPasync.h b/lib/eModbus/src/ModbusServerTCPasync.h
new file mode 100644
index 000000000..9f8ed3a80
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerTCPasync.h
@@ -0,0 +1,92 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_SERVER_TCP_ASYNC_H
+#define _MODBUS_SERVER_TCP_ASYNC_H
+
+#include "options.h"
+
+#include <list>
+#include <queue>
+#if USE_MUTEX
+#include <mutex> // NOLINT
+#endif
+#include <vector>
+
+#include <Arduino.h> // for millis()
+
+#if defined(ESP32)
+#include <AsyncTCP.h>
+#elif defined(ESP8266)
+#include <ESPAsyncTCP.h>
+#endif
+
+#include "ModbusServer.h"
+
+#if USE_MUTEX
+using std::lock_guard;
+#endif
+
+class ModbusServerTCPasync : public ModbusServer {
+  private:
+    class mb_client {
+        friend class ModbusServerTCPasync;
+
+      public:
+        mb_client(ModbusServerTCPasync * s, AsyncClient * c);
+        ~mb_client();
+
+      private:
+        void                        onData(uint8_t * data, size_t len);
+        void                        onPoll();
+        void                        onDisconnect();
+        void                        addResponseToOutbox(ModbusMessage * response);
+        void                        handleOutbox();
+        ModbusServerTCPasync *      server;
+        AsyncClient *               client;
+        uint32_t                    lastActiveTime;
+        ModbusMessage *             message;
+        Modbus::Error               error;
+        std::queue<ModbusMessage *> outbox;
+#if USE_MUTEX
+        std::mutex obLock; // outbox protection
+#endif
+    };
+
+
+  public:
+    // Constructor
+    ModbusServerTCPasync();
+
+    // Destructor: closes the connections
+    ~ModbusServerTCPasync();
+
+    // activeClients: return number of clients currently employed
+    uint16_t activeClients();
+
+    // start: create task with TCP server to accept requests
+    bool start(uint16_t port, uint8_t max_clients, uint32_t timeout, int coreID = -1);
+
+    // stop: drop all connections and kill server task
+    bool stop();
+
+    // isRunning: return true is server is running
+    bool isRunning();
+
+  protected:
+    inline void isInstance() {
+    }
+    void onClientConnect(AsyncClient * client);
+    void onClientDisconnect(mb_client * client);
+
+    AsyncServer *          server;
+    std::list<mb_client *> clients;
+    uint8_t                maxNoClients;
+    uint32_t               idle_timeout;
+#if USE_MUTEX
+    std::mutex cListLock; // client list protection
+#endif
+};
+
+#endif
diff --git a/lib/eModbus/src/ModbusServerTCPtemp.h b/lib/eModbus/src/ModbusServerTCPtemp.h
new file mode 100644
index 000000000..52341a3a4
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerTCPtemp.h
@@ -0,0 +1,433 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_SERVER_TCP_TEMP_H
+#define _MODBUS_SERVER_TCP_TEMP_H
+
+#include <Arduino.h>
+#include <mutex> // NOLINT
+#include "ModbusServer.h"
+#undef LOCAL_LOG_LEVEL
+// #define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+#include "Logging.h"
+
+extern "C" {
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+}
+
+using std::lock_guard;
+using std::mutex;
+using std::vector;
+
+template <typename ST, typename CT>
+class ModbusServerTCP : public ModbusServer {
+  public:
+    // Constructor
+    ModbusServerTCP();
+
+    // Destructor: closes the connections
+    ~ModbusServerTCP();
+
+    // activeClients: return number of clients currently employed
+    uint16_t activeClients();
+
+    // start: create task with TCP server to accept requests
+    bool start(uint16_t port, uint8_t max_clients, uint32_t timeout, int coreID = -1);
+
+    // stop: drop all connections and kill server task
+    bool stop();
+
+  protected:
+    // Prevent copy construction and assignment
+    ModbusServerTCP(ModbusServerTCP & m)             = delete;
+    ModbusServerTCP & operator=(ModbusServerTCP & m) = delete;
+
+    inline void isInstance() {
+    }
+
+    uint8_t      numClients;
+    TaskHandle_t serverTask;
+    uint16_t     serverPort;
+    uint32_t     serverTimeout;
+    bool         serverGoDown;
+    mutex        clientLock;
+
+    struct ClientData {
+        ClientData()
+            : task(nullptr)
+            , client(0)
+            , timeout(0)
+            , parent(nullptr) {
+        }
+        ClientData(TaskHandle_t t, CT & c, uint32_t to, ModbusServerTCP<ST, CT> * p)
+            : task(t)
+            , client(c)
+            , timeout(to)
+            , parent(p) {
+        }
+        ~ClientData() {
+            if (client) {
+                client.stop();
+            }
+            if (task != nullptr) {
+                vTaskDelete(task);
+                LOG_D("Killed client task %d\n", (uint32_t)task);
+            }
+        }
+        TaskHandle_t              task;
+        CT                        client;
+        uint32_t                  timeout;
+        ModbusServerTCP<ST, CT> * parent;
+    };
+    ClientData ** clients;
+
+    // serve: loop function for server task
+    static void serve(ModbusServerTCP<ST, CT> * myself);
+
+    // worker: loop function for client tasks
+    static void worker(ClientData * myData);
+
+    // receive: read data from TCP
+    ModbusMessage receive(CT & client, uint32_t timeWait);
+
+    // accept: start a task to receive requests and respond to a given client
+    bool accept(CT & client, uint32_t timeout, int coreID = -1);
+
+    // clientAvailable: return true,. if a client slot is currently unused
+    bool clientAvailable() {
+        return (numClients - activeClients()) > 0;
+    }
+};
+
+// Constructor
+template <typename ST, typename CT>
+ModbusServerTCP<ST, CT>::ModbusServerTCP()
+    : ModbusServer()
+    , numClients(0)
+    , serverTask(nullptr)
+    , serverPort(502)
+    , serverTimeout(20000)
+    , serverGoDown(false) {
+    clients = new ClientData *[numClients]();
+}
+
+// Destructor: closes the connections
+template <typename ST, typename CT>
+ModbusServerTCP<ST, CT>::~ModbusServerTCP() {
+    for (uint8_t i = 0; i < numClients; ++i) {
+        if (clients[i] != nullptr) {
+            delete clients[i];
+        }
+    }
+    delete[] clients;
+    serverGoDown = true;
+}
+
+// activeClients: return number of clients currently employed
+template <typename ST, typename CT>
+uint16_t ModbusServerTCP<ST, CT>::activeClients() {
+    uint8_t cnt = 0;
+    for (uint8_t i = 0; i < numClients; ++i) {
+        // Current slot could have been previously used - look for cleared task handles
+        if (clients[i] != nullptr) {
+            // Empty task handle?
+            if (clients[i]->task == nullptr) {
+                // Yes. Delete entry and init client pointer
+                lock_guard<mutex> cL(clientLock);
+                delete clients[i];
+                LOG_V("Delete client %d\n", i);
+                clients[i] = nullptr;
+            }
+        }
+        if (clients[i] != nullptr)
+            cnt++;
+    }
+    return cnt;
+}
+
+// start: create task with TCP server to accept requests
+template <typename ST, typename CT>
+bool ModbusServerTCP<ST, CT>::start(uint16_t port, uint8_t max_clients, uint32_t timeout, int coreID) {
+    // Task already running?
+    if (serverTask != nullptr) {
+        // Yes. stop it first
+        stop();
+    }
+    // Does the required number of slots fit?
+    if (numClients != max_clients) {
+        // No. Drop array and allocate a new one
+        delete[] clients;
+        // Now allocate a new one
+        numClients = max_clients;
+        clients    = new ClientData *[numClients]();
+    }
+    serverPort    = port;
+    serverTimeout = timeout;
+    serverGoDown  = false;
+
+    // Create unique task name
+    char taskName[18];
+    snprintf(taskName, 18, "MBserve%04X", port);
+
+    // Start task to handle the client
+    xTaskCreatePinnedToCore((TaskFunction_t)&serve, taskName, SERVER_TASK_STACK, this, 5, &serverTask, coreID >= 0 ? coreID : NULL);
+    LOG_D("Server task %s started (%d).\n", taskName, (uint32_t)serverTask);
+
+    // Wait two seconds for it to establish
+    delay(2000);
+
+    return true;
+}
+
+// stop: drop all connections and kill server task
+template <typename ST, typename CT>
+bool ModbusServerTCP<ST, CT>::stop() {
+    // Check for clients still connected
+    for (uint8_t i = 0; i < numClients; ++i) {
+        // Client is alive?
+        if (clients[i] != nullptr) {
+            // Yes. Close the connection
+            delete clients[i];
+            clients[i] = nullptr;
+        }
+    }
+    if (serverTask != nullptr) {
+        // Signal server task to stop
+        serverGoDown = true;
+        delay(5000);
+        LOG_D("Killed server task %d\n", (uint32_t)(serverTask));
+        serverTask   = nullptr;
+        serverGoDown = false;
+    }
+    return true;
+}
+
+// accept: start a task to receive requests and respond to a given client
+template <typename ST, typename CT>
+bool ModbusServerTCP<ST, CT>::accept(CT & client, uint32_t timeout, int coreID) {
+    // Look for an empty client slot
+    for (uint8_t i = 0; i < numClients; ++i) {
+        // Empty slot?
+        if (clients[i] == nullptr) {
+            // Yes. allocate new client data in slot
+            clients[i] = new ClientData(0, client, timeout, this);
+
+            // Create unique task name
+            char taskName[18];
+            snprintf(taskName, 18, "MBsrv%02Xclnt", i);
+
+            // Start task to handle the client
+            xTaskCreatePinnedToCore((TaskFunction_t)&worker, taskName, SERVER_TASK_STACK, clients[i], 5, &clients[i]->task, coreID >= 0 ? coreID : NULL);
+            LOG_D("Started client %d task %d\n", i, (uint32_t)(clients[i]->task));
+
+            return true;
+        }
+    }
+    LOG_D("No client slot available.\n");
+    return false;
+}
+
+template <typename ST, typename CT>
+void ModbusServerTCP<ST, CT>::serve(ModbusServerTCP<ST, CT> * myself) {
+    // need a local scope here to delete the server at termination time
+    if (1) {
+        // Set up server with given port
+        ST server(myself->serverPort);
+
+        // Start it
+        server.begin();
+
+        // Loop until being killed
+        while (!myself->serverGoDown) {
+            // Do we have clients left to use?
+            if (myself->clientAvailable()) {
+                // Yes. accept one, when it connects
+                CT ec = server.accept();
+                // Did we get a connection?
+                if (ec) {
+                    // Yes. Forward it to the Modbus server
+                    myself->accept(ec, myself->serverTimeout, 0);
+                    LOG_D("Accepted connection - %d clients running\n", myself->activeClients());
+                }
+            }
+            // Give scheduler room to breathe
+            delay(10);
+        }
+        LOG_E("Server going down\n");
+        // We must go down
+        SERVER_END;
+    }
+    vTaskDelete(NULL);
+}
+
+template <typename ST, typename CT>
+void ModbusServerTCP<ST, CT>::worker(ClientData * myData) {
+    // Get own reference data in handier form
+    CT       myClient  = myData->client;
+    uint32_t myTimeOut = myData->timeout;
+    // TaskHandle_t myTask = myData->task;
+    ModbusServerTCP<ST, CT> * myParent      = myData->parent;
+    unsigned long             myLastMessage = millis();
+
+    LOG_D("Worker started, timeout=%d\n", myTimeOut);
+
+    // loop forever, if timeout is 0, or until timeout was hit
+    while (myClient.connected() && (!myTimeOut || (millis() - myLastMessage < myTimeOut))) {
+        ModbusMessage response; // Data buffer to hold prepared response
+        // Get a request
+        if (myClient.available()) {
+            response.clear();
+            ModbusMessage m = myParent->receive(myClient, 100);
+
+            // has it the minimal length (6 bytes TCP header plus serverID plus FC)?
+            if (m.size() >= 8) {
+                {
+                    LOCK_GUARD(cntLock, myParent->m);
+                    myParent->messageCount++;
+                }
+                // Extract request data
+                ModbusMessage request;
+                request.add(m.data() + 6, m.size() - 6);
+
+                // Protocol ID shall be 0x0000 - is it?
+                if (m[2] == 0 && m[3] == 0) {
+                    // ServerID shall be at [6], FC at [7]. Check both
+                    if (myParent->isServerFor(request.getServerID())) {
+                        // Server is correct - in principle. Do we serve the FC?
+                        MBSworker callBack = myParent->getWorker(request.getServerID(), request.getFunctionCode());
+                        if (callBack) {
+                            // Yes, we do.
+                            // Invoke the worker method to get a response
+                            ModbusMessage data = callBack(request);
+                            // Process Response
+                            // One of the predefined types?
+                            if (data[0] == 0xFF && (data[1] == 0xF0 || data[1] == 0xF1)) {
+                                // Yes. Check it
+                                switch (data[1]) {
+                                case 0xF0: // NIL
+                                    response.clear();
+                                    LOG_D("NIL response\n");
+                                    break;
+                                case 0xF1: // ECHO
+                                    response = request;
+                                    if (request.getFunctionCode() == WRITE_MULT_REGISTERS || request.getFunctionCode() == WRITE_MULT_COILS) {
+                                        response.resize(6);
+                                    }
+                                    LOG_D("ECHO response\n");
+                                    break;
+                                default: // Will not get here!
+                                    break;
+                                }
+                            } else {
+                                // No. User provided data response
+                                response = data;
+                                LOG_D("Data response\n");
+                            }
+                        } else {
+                            // No, function code is not served here
+                            response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_FUNCTION);
+                        }
+                    } else {
+                        // No, serverID is not served here
+                        response.setError(request.getServerID(), request.getFunctionCode(), INVALID_SERVER);
+                    }
+                } else {
+                    // No, protocol ID was something weird
+                    response.setError(request.getServerID(), request.getFunctionCode(), TCP_HEAD_MISMATCH);
+                }
+            }
+            delay(1);
+            // Do we have a response to send?
+            if (response.size() >= 3) {
+                // Yes. Do it now.
+                // Cut off length and request data, then update TCP header
+                m.resize(4);
+                m.add(static_cast<uint16_t>(response.size()));
+                // Append response
+                m.append(response);
+                myClient.write(m.data(), m.size());
+                HEXDUMP_V("Response", m.data(), m.size());
+                // count error responses
+                if (response.getError() != SUCCESS) {
+                    LOCK_GUARD(cntLock, myParent->m);
+                    myParent->errorCount++;
+                }
+            }
+            // We did something communicationally - rewind timeout timer
+            myLastMessage = millis();
+        }
+        delay(1);
+    }
+
+    if (millis() - myLastMessage >= myTimeOut) {
+        // Timeout!
+        LOG_D("Worker stopping due to timeout.\n");
+    } else {
+        // Disconnected!
+        LOG_D("Worker stopping due to client disconnect.\n");
+    }
+
+    // Read away all that may still hang in the buffer
+    while (myClient.read() != -1) {
+    }
+    // Now stop the client
+    myClient.stop();
+
+    {
+        lock_guard<mutex> cL(myParent->clientLock);
+        myData->task = nullptr;
+    }
+
+    delay(50);
+    vTaskDelete(NULL);
+}
+
+// receive: get request via Client connection
+template <typename ST, typename CT>
+ModbusMessage ModbusServerTCP<ST, CT>::receive(CT & client, uint32_t timeWait) {
+    unsigned long  lastMillis = millis(); // Timer to check for timeout
+    ModbusMessage  m;                     // to take read data
+    uint16_t       lengthVal = 0;
+    uint16_t       cnt       = 0;
+    const uint16_t BUFFERSIZE(300);
+    uint8_t        buffer[BUFFERSIZE];
+
+    // wait for sufficient packet data or timeout
+    while ((millis() - lastMillis < timeWait) && ((cnt < 6) || (cnt < lengthVal)) && (cnt < BUFFERSIZE)) {
+        // Is there data waiting?
+        if (client.available()) {
+            buffer[cnt] = client.read();
+            // Are we at the TCP header length field byte #1?
+            if (cnt == 4)
+                lengthVal = buffer[cnt] << 8;
+            // Are we at the TCP header length field byte #2?
+            if (cnt == 5) {
+                lengthVal |= buffer[cnt];
+                lengthVal += 6;
+            }
+            cnt++;
+            // Rewind EOT and timeout timers
+            lastMillis = millis();
+        } else {
+            delay(1); // Give scheduler room to breathe
+        }
+    }
+    // Did we receive some data?
+    if (cnt) {
+        // Yes. Is it too much?
+        if (cnt >= BUFFERSIZE) {
+            // Yes, likely a buffer overflow of some sort
+            // Adjust message size in TCP header
+            buffer[4] = (cnt >> 8) & 0xFF;
+            buffer[5] = cnt & 0xFF;
+            LOG_E("Potential buffer overrun (>%d)!\n", cnt);
+        }
+        // Get as much buffer as was read
+        m.add(buffer, cnt);
+    }
+    return m;
+}
+
+#endif
diff --git a/lib/eModbus/src/ModbusServerWiFi.h b/lib/eModbus/src/ModbusServerWiFi.h
new file mode 100644
index 000000000..453cddf43
--- /dev/null
+++ b/lib/eModbus/src/ModbusServerWiFi.h
@@ -0,0 +1,16 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_SERVER_WIFI_H
+#define _MODBUS_SERVER_WIFI_H
+#include "options.h"
+#include <WiFi.h>
+
+#undef SERVER_END
+#define SERVER_END server.end();
+
+#include "ModbusServerTCPtemp.h"
+using ModbusServerWiFi = ModbusServerTCP<WiFiServer, WiFiClient>;
+
+#endif
diff --git a/lib/eModbus/src/ModbusTypeDefs.cpp b/lib/eModbus/src/ModbusTypeDefs.cpp
new file mode 100644
index 000000000..7868cfca2
--- /dev/null
+++ b/lib/eModbus/src/ModbusTypeDefs.cpp
@@ -0,0 +1,66 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "ModbusTypeDefs.h"
+
+#ifndef MINIMAL
+
+using Modbus::FCType;
+using Modbus::FCT;
+
+// Initialize function code type table
+FCType FCT::table[] = {
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FC01_TYPE, FC01_TYPE, FC01_TYPE, FC01_TYPE, FC01_TYPE, FC01_TYPE, FC07_TYPE,  // 0x0.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCGENERIC, FCILLEGAL, FCILLEGAL, FC07_TYPE, FC07_TYPE, FCILLEGAL, FCILLEGAL, FC0F_TYPE,  // 0x0.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FC10_TYPE, FC07_TYPE, FCILLEGAL, FCILLEGAL, FCGENERIC, FCGENERIC, FC16_TYPE, FCGENERIC,  // 0x1.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FC18_TYPE, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x1.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x2.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCGENERIC, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x2.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x3.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x3.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCUSER,     // 0x4.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCUSER,    FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x4.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x5.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x5.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCUSER,    FCUSER,    FCUSER,    FCUSER,     // 0x6.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCUSER,    FCILLEGAL,  // 0x6.
+// 0x.0      0x.1       0x.2       0x.3       0x.4       0x.5       0x.6       0x.7
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x7.
+// 0x.8      0x.9       0x.A       0x.B       0x.C       0x.D       0x.E       0x.F
+  FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL, FCILLEGAL,  // 0x7.
+};
+
+// FCT::getType: get the function code type for a given function code
+FCType FCT::getType(uint8_t functionCode) {
+  return table[functionCode & 0x7F];
+}
+
+// setType: change the type of a function code.
+// This is possible only for the codes undefined yet and will return
+// the effective type
+FCType FCT::redefineType(uint8_t functionCode, const FCType type) {
+  uint8_t fc = functionCode & 0x7F;
+  
+  // Allow modifications for yet undefined codes only
+  if (table[fc] == FCILLEGAL) {
+    table[fc] = type;
+  }
+  return table[fc];
+}
+
+#endif
diff --git a/lib/eModbus/src/ModbusTypeDefs.h b/lib/eModbus/src/ModbusTypeDefs.h
new file mode 100644
index 000000000..cd0217810
--- /dev/null
+++ b/lib/eModbus/src/ModbusTypeDefs.h
@@ -0,0 +1,139 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _MODBUS_TYPEDEFS_H
+#define _MODBUS_TYPEDEFS_H
+#include <stdint.h>
+#include <stddef.h>
+#include <cstdint>
+
+namespace Modbus {
+
+enum FunctionCode : uint8_t {
+  ANY_FUNCTION_CODE       = 0x00, // Only valid for server to register function codes
+  READ_COIL               = 0x01,
+  READ_DISCR_INPUT        = 0x02,
+  READ_HOLD_REGISTER      = 0x03,
+  READ_INPUT_REGISTER     = 0x04,
+  WRITE_COIL              = 0x05,
+  WRITE_HOLD_REGISTER     = 0x06,
+  READ_EXCEPTION_SERIAL   = 0x07,
+  DIAGNOSTICS_SERIAL      = 0x08,
+  READ_COMM_CNT_SERIAL    = 0x0B,
+  READ_COMM_LOG_SERIAL    = 0x0C,
+  WRITE_MULT_COILS        = 0x0F,
+  WRITE_MULT_REGISTERS    = 0x10,
+  REPORT_SERVER_ID_SERIAL = 0x11,
+  READ_FILE_RECORD        = 0x14,
+  WRITE_FILE_RECORD       = 0x15,
+  MASK_WRITE_REGISTER     = 0x16,
+  R_W_MULT_REGISTERS      = 0x17,
+  READ_FIFO_QUEUE         = 0x18,
+  ENCAPSULATED_INTERFACE  = 0x2B,
+  USER_DEFINED_41         = 0x41,
+  USER_DEFINED_42         = 0x42,
+  USER_DEFINED_43         = 0x43,
+  USER_DEFINED_44         = 0x44,
+  USER_DEFINED_45         = 0x45,
+  USER_DEFINED_46         = 0x46,
+  USER_DEFINED_47         = 0x47,
+  USER_DEFINED_48         = 0x48,
+  USER_DEFINED_64         = 0x64,
+  USER_DEFINED_65         = 0x65,
+  USER_DEFINED_66         = 0x66,
+  USER_DEFINED_67         = 0x67,
+  USER_DEFINED_68         = 0x68,
+  USER_DEFINED_69         = 0x69,
+  USER_DEFINED_6A         = 0x6A,
+  USER_DEFINED_6B         = 0x6B,
+  USER_DEFINED_6C         = 0x6C,
+  USER_DEFINED_6D         = 0x6D,
+  USER_DEFINED_6E         = 0x6E,
+};
+
+enum Error : uint8_t {
+  SUCCESS                = 0x00,
+  ILLEGAL_FUNCTION       = 0x01,
+  ILLEGAL_DATA_ADDRESS   = 0x02,
+  ILLEGAL_DATA_VALUE     = 0x03,
+  SERVER_DEVICE_FAILURE  = 0x04,
+  ACKNOWLEDGE            = 0x05,
+  SERVER_DEVICE_BUSY     = 0x06,
+  NEGATIVE_ACKNOWLEDGE   = 0x07,
+  MEMORY_PARITY_ERROR    = 0x08,
+  GATEWAY_PATH_UNAVAIL   = 0x0A,
+  GATEWAY_TARGET_NO_RESP = 0x0B,
+  TIMEOUT                = 0xE0,
+  INVALID_SERVER         = 0xE1,
+  CRC_ERROR              = 0xE2, // only for Modbus-RTU
+  FC_MISMATCH            = 0xE3,
+  SERVER_ID_MISMATCH     = 0xE4,
+  PACKET_LENGTH_ERROR    = 0xE5,
+  PARAMETER_COUNT_ERROR  = 0xE6,
+  PARAMETER_LIMIT_ERROR  = 0xE7,
+  REQUEST_QUEUE_FULL     = 0xE8,
+  ILLEGAL_IP_OR_PORT     = 0xE9,
+  IP_CONNECTION_FAILED   = 0xEA,
+  TCP_HEAD_MISMATCH      = 0xEB,
+  EMPTY_MESSAGE          = 0xEC,
+  ASCII_FRAME_ERR        = 0xED,
+  ASCII_CRC_ERR          = 0xEE,
+  ASCII_INVALID_CHAR     = 0xEF,
+  BROADCAST_ERROR        = 0xF0,
+  UNDEFINED_ERROR        = 0xFF  // otherwise uncovered communication error
+};
+
+#ifndef MINIMAL
+
+// Constants for float and double re-ordering
+#define SWAP_BYTES     0x01
+#define SWAP_REGISTERS 0x02
+#define SWAP_WORDS     0x04
+#define SWAP_NIBBLES   0x08
+
+const uint8_t swapTables[8][8] = {
+  { 0, 1, 2, 3, 4, 5, 6, 7 },  // no swap
+  { 1, 0, 3, 2, 5, 4, 7, 6 },  // bytes only
+  { 2, 3, 0, 1, 6, 7, 4, 5 },  // registers only
+  { 3, 2, 1, 0, 7, 6, 5, 4 },  // registers and bytes
+  { 4, 5, 6, 7, 0, 1, 2, 3 },  // words only (double)
+  { 5, 4, 7, 6, 1, 0, 3, 2 },  // words and bytes (double)
+  { 6, 7, 4, 5, 2, 3, 0, 1 },  // words and registers (double)
+  { 7, 6, 5, 4, 3, 2, 1, 0 }   // Words, registers and bytes (double)
+};
+
+enum FCType : uint8_t {
+  FC01_TYPE,         // Two uint16_t parameters (FC 0x01, 0x02, 0x03, 0x04, 0x05, 0x06)
+  FC07_TYPE,         // no additional parameter (FCs 0x07, 0x0b, 0x0c, 0x11)
+  FC0F_TYPE,         // two uint16_t parameters, a uint8_t length byte and a uint16_t* pointer to array of bytes (FC 0x0f)
+  FC10_TYPE,         // two uint16_t parameters, a uint8_t length byte and a uint8_t* pointer to array of words (FC 0x10)
+  FC16_TYPE,         // three uint16_t parameters (FC 0x16)
+  FC18_TYPE,         // one uint16_t parameter (FC 0x18)
+  FCGENERIC,         // for FCs not yet explicitly coded (or too complex)
+  FCUSER,            // No checks except the server ID
+  FCILLEGAL,         // not allowed function codes
+};
+
+// FCT: static class to hold the types of function codes
+class FCT {
+protected:
+  static FCType table[128];     // data table
+  FCT() = delete;                // No instances allowed
+  FCT(const FCT&) = delete;      // No copy constructor
+  FCT& operator=(const FCT& other) = delete; // No assignment either
+public:
+  // getType: get the function code type for a given function code
+  static FCType getType(uint8_t functionCode);
+
+  // setType: change the type of a function code.
+  // This is possible only for the codes undefined yet and will return
+  // the effective type
+  static FCType redefineType(uint8_t functionCode, const FCType type = FCUSER);
+};
+
+#endif
+
+}  // namespace Modbus
+
+#endif
diff --git a/lib/eModbus/src/RTUutils.cpp b/lib/eModbus/src/RTUutils.cpp
new file mode 100644
index 000000000..d360c95af
--- /dev/null
+++ b/lib/eModbus/src/RTUutils.cpp
@@ -0,0 +1,467 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#include "options.h"
+#include "ModbusMessage.h"
+#include "RTUutils.h"
+#undef LOCAL_LOG_LEVEL
+// #define LOCAL_LOG_LEVEL LOG_LEVEL_VERBOSE
+#include "Logging.h"
+
+#if HAS_FREERTOS
+// calcCRC: calculate Modbus CRC16 on a given array of bytes
+uint16_t RTUutils::calcCRC(const uint8_t *data, uint16_t len) {
+  // CRC16 pre-calculated tables
+  const uint8_t crcHiTable[] = {
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
+    0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
+    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,
+    0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81,
+    0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
+    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,
+    0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
+    0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
+    0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01,
+    0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
+    0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
+    0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01,
+    0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
+    0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81,
+    0x40
+  };
+
+  const uint8_t crcLoTable[] = {
+    0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4,
+    0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09,
+    0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD,
+    0x1D, 0x1C, 0xDC, 0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
+    0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7,
+    0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
+    0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE,
+    0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
+    0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1, 0x63, 0xA3, 0xA2,
+    0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F,
+    0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB,
+    0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
+    0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91,
+    0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C,
+    0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E, 0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88,
+    0x48, 0x49, 0x89, 0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
+    0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80,
+    0x40
+  };
+
+  uint8_t crcHi = 0xFF;
+  uint8_t crcLo = 0xFF;
+  uint8_t index;
+
+  while (len--) {
+    index = crcLo ^ *data++;
+    crcLo = crcHi ^ crcHiTable[index];
+    crcHi = crcLoTable[index];
+  }
+  return (crcHi << 8 | crcLo);
+}
+
+// calcCRC: calculate Modbus CRC16 on a given message
+uint16_t RTUutils::calcCRC(ModbusMessage msg) {
+  return calcCRC(msg.data(), msg.size());
+}
+
+
+// validCRC #1: check the given CRC in a block of data for correctness
+bool RTUutils::validCRC(const uint8_t *data, uint16_t len) {
+  return validCRC(data, len - 2, data[len - 2] | (data[len - 1] << 8));
+}
+
+// validCRC #2: check the CRC of a block of data against a given one for equality
+bool RTUutils::validCRC(const uint8_t *data, uint16_t len, uint16_t CRC) {
+  uint16_t crc16 = calcCRC(data, len);
+  if (CRC == crc16) return true;
+  return false;
+}
+
+// validCRC #3: check the given CRC in a message for correctness
+bool RTUutils::validCRC(ModbusMessage msg) {
+  return validCRC(msg.data(), msg.size() - 2, msg[msg.size() - 2] | (msg[msg.size() - 1] << 8));
+}
+
+// validCRC #4: check the CRC of a message against a given one for equality
+bool RTUutils::validCRC(ModbusMessage msg, uint16_t CRC) {
+  return validCRC(msg.data(), msg.size(), CRC);
+}
+
+// addCRC: calculate the CRC for a given RTUMessage and add it to the end
+void RTUutils::addCRC(ModbusMessage& raw) {
+  uint16_t crc16 = calcCRC(raw.data(), raw.size());
+  raw.push_back(crc16 & 0xff);
+  raw.push_back((crc16 >> 8) & 0xFF);
+}
+
+// calculateInterval: determine the minimal gap time between messages
+uint32_t RTUutils::calculateInterval(uint32_t baudRate) {
+  uint32_t interval = 0;
+
+  // silent interval is at least 3.5x character time
+  interval = 35000000UL / baudRate;  // 3.5 * 10 bits * 1000 µs * 1000 ms / baud
+  if (interval < 1750) interval = 1750;       // lower limit according to Modbus RTU standard
+  LOG_V("Calc interval(%u)=%u\n", baudRate, interval);
+  return interval;
+}
+
+// send: send a message via Serial, watching interval times - including CRC!
+void RTUutils::send(Stream& serial, unsigned long& lastMicros, uint32_t interval, RTScallback rts, const uint8_t *data, uint16_t len, bool ASCIImode) {
+  // Clear serial buffers
+  while (serial.available()) serial.read();
+  
+  // Treat ASCII differently
+  if (ASCIImode) {
+    // Toggle rtsPin, if necessary
+    rts(HIGH);
+    // Yes, ASCII mode. Send lead-in
+    serial.write(':');
+
+    uint16_t cnt = len;
+    uint8_t crc = 0;
+    uint8_t *cp = (uint8_t *)data;
+
+    // Loop over all bytes of the message
+    while (cnt--) {
+      // Write two nibbles as ASCII characters
+      serial.write(ASCIIwrite[(*cp >> 4) & 0x0F]);
+      serial.write(ASCIIwrite[*cp & 0x0F]);
+      // Advance CRC
+      crc += *cp;
+      // Next byte
+      cp++;
+    }
+    // Finalize CRC (2's complement)
+    crc = ~crc;
+    crc++;
+    // Write ist - two nibbles as ASCII characters
+    serial.write(ASCIIwrite[(crc >> 4) & 0x0F]);
+    serial.write(ASCIIwrite[crc & 0x0F]);
+    
+    // Send lead-out
+    serial.write("\r\n");
+    serial.flush();
+    // Toggle rtsPin, if necessary
+    rts(LOW);
+  } else {
+    // RTU mode
+    uint16_t crc16 = calcCRC(data, len);
+
+    // Respect interval - we must not toggle rtsPin before
+    if (micros() - lastMicros < interval) delayMicroseconds(interval - (micros() - lastMicros));
+
+    // Toggle rtsPin, if necessary
+    rts(HIGH);
+    // Write message
+    serial.write(data, len);
+    // Write CRC in LSB order
+    serial.write(crc16 & 0xff);
+    serial.write((crc16 >> 8) & 0xFF);
+    serial.flush();
+    // Toggle rtsPin, if necessary
+    rts(LOW);
+  }
+
+  HEXDUMP_D("Sent packet", data, len);
+
+  // Mark end-of-message time for next interval
+  lastMicros = micros();
+}
+
+// send: send a message via Serial, watching interval times - including CRC!
+void RTUutils::send(Stream& serial, unsigned long& lastMicros, uint32_t interval, RTScallback rts, ModbusMessage raw, bool ASCIImode) {
+  send(serial, lastMicros, interval, rts, raw.data(), raw.size(), ASCIImode);
+}
+
+// receive: get (any) message from Serial, taking care of timeout and interval
+ModbusMessage RTUutils::receive(uint8_t caller, Stream& serial, uint32_t timeout, unsigned long& lastMicros, uint32_t interval, bool ASCIImode, bool skipLeadingZeroBytes) {
+  // Allocate initial receive buffer size: 1 block of BUFBLOCKSIZE bytes
+  const uint16_t BUFBLOCKSIZE(512);
+  uint8_t *buffer = new uint8_t[BUFBLOCKSIZE];
+  ModbusMessage rv;
+
+  // Index into buffer
+  uint16_t bufferPtr = 0;
+  // Byte read
+  int b = 0; 
+
+  // State machine states, RTU mode
+  enum STATES : uint8_t { WAIT_DATA = 0, IN_PACKET, DATA_READ, FINISHED };
+
+  // State machine states, ASCII mode
+  enum ASTATES : uint8_t { A_WAIT_DATA = 0, A_DATA, A_WAIT_LEAD_OUT, A_FINISHED };
+
+  uint8_t state;
+
+  // Timeout tracker
+  unsigned long TimeOut = millis();
+
+  // RTU mode?
+  if (!ASCIImode) {
+    // Yes.
+    state = WAIT_DATA;
+    // interval tracker 
+    lastMicros = micros();
+  
+    while (state != FINISHED) {
+      switch (state) {
+      // WAIT_DATA: await first data byte, but watch timeout
+      case WAIT_DATA:
+        // Blindly try to read a byte
+        b = serial.read();
+        // Did we get one?
+        if (b >= 0) {
+          // Yes. Note the time.
+          lastMicros = micros();
+          // Do we need to skip it, if it is zero?
+          if (b > 0 || !skipLeadingZeroBytes) {
+            // No, we can go process it regularly
+            buffer[bufferPtr++] = b;
+            state = IN_PACKET;
+          } 
+        } else {
+          // No, we had no byte. Just check the timeout period
+          if (millis() - TimeOut >= timeout) {
+            rv.push_back(TIMEOUT);
+            state = FINISHED;
+          }
+          delay(1);
+        }
+        break;
+      // IN_PACKET: read data until a gap of at least _interval time passed without another byte arriving
+      case IN_PACKET:
+        // tight loop until finished reading or error
+        while (state == IN_PACKET) {
+          // Is there a byte?
+          while (serial.available()) {
+            // Yes, collect it
+            buffer[bufferPtr++] = serial.read();
+            // Mark time of last byte
+            lastMicros = micros();
+            // Buffer full?
+            if (bufferPtr >= BUFBLOCKSIZE) {
+              // Yes. Something fishy here - bail out!
+              rv.push_back(PACKET_LENGTH_ERROR);
+              state = FINISHED;
+              break;
+            }
+          } 
+          // No more byte read
+          if (state == IN_PACKET) {
+            // Are we past the interval gap?
+            if (micros() - lastMicros >= interval) {
+              // Yes, terminate reading
+              LOG_V("%c/%ldus without data after %u\n", (const char)caller, micros() - lastMicros, bufferPtr);
+              state = DATA_READ;
+              break;
+            }
+          }
+        }
+        break;
+      // DATA_READ: successfully gathered some data. Prepare return object.
+      case DATA_READ:
+        // Did we get a sensible buffer length?
+        LOG_V("%c/", (const char)caller);
+        HEXDUMP_V("Raw buffer received", buffer, bufferPtr);
+        if (bufferPtr >= 4)
+        {
+          // Yes. Check CRC
+          if (!validCRC(buffer, bufferPtr)) {
+            // Ooops. CRC is wrong.
+            rv.push_back(CRC_ERROR);
+          } else {
+            // CRC was fine, Now allocate response object without the CRC
+            for (uint16_t i = 0; i < bufferPtr - 2; ++i) {
+              rv.push_back(buffer[i]);
+            }
+          }
+        } else {
+          // No, packet was too short for anything usable. Return error
+          rv.push_back(PACKET_LENGTH_ERROR);
+        }
+        state = FINISHED;
+        break;
+      // FINISHED: we are done, clean up.
+      case FINISHED:
+        // CLear serial buffer in case something is left trailing
+        // May happen with servers too slow!
+        while (serial.available()) serial.read();
+        break;
+      }
+    }
+  } else {
+    // We are in ASCII mode.
+    state = A_WAIT_DATA;
+
+    // Track nibbles in a byte
+    bool byteComplete = true; 
+
+    // Track bytes read
+    bool hadBytes = false;
+
+    // ASCII crc byte
+    uint8_t crc = 0;
+
+    while (state != A_FINISHED) {
+      // Always watch timeout - 1s
+      if (millis() - TimeOut >= timeout) {
+        // Timeout! Bail out with error
+        rv.push_back(TIMEOUT);
+        state = A_FINISHED;
+      } else {
+        // Still in time. Check for another byte on serial
+        if (!hadBytes && serial.available()) {
+          b = serial.read();
+          if (b >= 0) {
+            hadBytes = true;
+          }
+        }
+        // Only use state machine with new data arrived
+        if (hadBytes) {
+          // First reset timeout
+          TimeOut = millis();
+          // Is it a valid character?
+          if ((b & 0x80) || ASCIIread[b] == 0xFF) {
+            // No. Report error and leave.
+            rv.clear();
+            rv.push_back(ASCII_INVALID_CHAR);
+            hadBytes = false;
+            state = A_FINISHED;
+          } else {
+            // Yes, is valid. Furtheron use interpreted byte
+            b = ASCIIread[b];
+            switch (state) {
+            // A_WAIT_DATA: await lead-in byte ':'
+            case A_WAIT_DATA:
+              // Is it the lead-in?
+              if (b == 0xF0) {
+                // Yes, proceed to data read state
+                state = A_DATA;
+              }
+              // byte was consumed in any case
+              hadBytes = false;
+              break;
+            // A_DATA: read data as it comes
+            case A_DATA:
+              // Lead-out byte 1 received?
+              if (b == 0xF1) {
+                // Yes. Was last buffer byte completed?
+                if (byteComplete) {
+                  // Yes. Move to final state
+                  state = A_WAIT_LEAD_OUT;
+                } else {
+                  // No, signal with error
+                  rv.push_back(PACKET_LENGTH_ERROR);
+                  state = A_FINISHED;
+                }
+              } else {
+                // No lead-out, must be data byte.
+                // Is it valid?
+                if (b < 0xF0) {
+                  // Yes. Add it into current buffer byte
+                  buffer[bufferPtr] <<= 4;
+                  buffer[bufferPtr] += (b & 0x0F);
+                  // Advance nibble
+                  byteComplete = !byteComplete;
+                  // Was it the second of the byte?
+                  if (byteComplete) {
+                    // Yes. Advance CRC and move buffer pointer by one
+                    crc += buffer[bufferPtr];
+                    bufferPtr++;
+                    buffer[bufferPtr] = 0;
+                  }
+                } else {
+                  // No, garbage. report error
+                  rv.push_back(ASCII_INVALID_CHAR);
+                  state = A_FINISHED;
+                }
+              }
+              hadBytes = false;
+              break;
+            // A_WAIT_LEAD_OUT: await \n
+            case A_WAIT_LEAD_OUT:
+              if (b == 0xF2) {
+                // Lead-out byte 2 received. Transfer buffer to returned message
+                LOG_V("%c/", (const char)caller);
+                HEXDUMP_V("Raw buffer received", buffer, bufferPtr);
+                // Did we get a sensible buffer length?
+                if (bufferPtr >= 3)
+                {
+                  // Yes. Was the CRC calculated correctly?
+                  if (crc == 0) {
+                    // Yes, reduce buffer by 1 to get rid of CRC byte...
+                    bufferPtr--;
+                    // Move data into returned message
+                    for (uint16_t i = 0; i < bufferPtr; ++i) {
+                      rv.push_back(buffer[i]);
+                    }
+                  } else {
+                    // No, CRC calculation seems to have failed
+                    rv.push_back(ASCII_CRC_ERR);
+                  }
+                } else {
+                  // No, packet was too short for anything usable. Return error
+                  rv.push_back(PACKET_LENGTH_ERROR);
+                }
+              } else {
+                // No lead out byte 2, but something else - report error.
+                rv.push_back(ASCII_FRAME_ERR);
+              }
+              state = A_FINISHED;
+              break;
+            // A_FINISHED: Message completed
+            case A_FINISHED:
+              // Clean up serial buffer
+              while (serial.available()) serial.read();
+              break;
+            }
+          }
+        } else {
+          // No data received, so give the task scheduler room to breathe
+          delay(1);
+        }
+      }
+    }
+  }
+  // Deallocate buffer
+  delete[] buffer;
+
+  LOG_D("%c/", (const char)caller);
+  HEXDUMP_D("Received packet", rv.data(), rv.size());
+
+  return rv;
+}
+
+// Lower 7 bit ASCII characters - all invalid are set to 0xFF
+const char RTUutils::ASCIIread[] = { 
+  /* 00-07 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 08-0F */ 0xFF, 0xFF, 0xF2, 0xFF, 0xFF, 0xF1, 0xFF, 0xFF,  // LF + CR
+  /* 10-17 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 18-1F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 20-27 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 28-2F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 30-37 */    0,    1,    2,    3,    4,    5,    6,    7,  // digits 0-7
+  /* 38-3F */    8,    9, 0xF0, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,  // digits 8 + 9, :
+  /* 40-47 */ 0xFF,   10,   11,   12,   13,   14,   15, 0xFF,  // digits A-F
+  /* 48-4F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 50-57 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 58-5F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 60-67 */ 0xFF,   10,   11,   12,   13,   14,   15, 0xFF,  // digits a-f
+  /* 68-6F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 70-77 */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 
+  /* 78-7F */ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF 
+};
+
+// Writable ASCII chars for hex digits
+const char RTUutils::ASCIIwrite[] = { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 
+                                      0x38, 0x39, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46 
+};
+#endif
diff --git a/lib/eModbus/src/RTUutils.h b/lib/eModbus/src/RTUutils.h
new file mode 100644
index 000000000..f50d8f449
--- /dev/null
+++ b/lib/eModbus/src/RTUutils.h
@@ -0,0 +1,76 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _RTU_UTILS_H
+#define _RTU_UTILS_H
+#include <stdint.h>
+#if NEED_UART_PATCH
+#include <soc/uart_struct.h>
+#endif
+#include <vector>
+#include "Stream.h"
+#include "ModbusTypeDefs.h"
+#include <functional> 
+
+typedef std::function<void(bool level)> RTScallback;
+
+using namespace Modbus;  // NOLINT
+
+// RTUutils is bundling the send, receive and CRC functions for Modbus RTU communications.
+// RTU server and client will make use of it. 
+// All functions are static!
+class RTUutils {
+public:
+  friend class ModbusClientRTU;
+  friend class ModbusServerRTU;
+
+// calcCRC: calculate the CRC16 value for a given block of data
+  static uint16_t calcCRC(const uint8_t *data, uint16_t len);
+
+// calcCRC: calculate the CRC16 value for a given block of data
+  static uint16_t calcCRC(ModbusMessage msg);
+
+// validCRC #1: check the CRC in a block of data for validity
+  static bool validCRC(const uint8_t *data, uint16_t len);
+
+// validCRC #2: check the CRC of a block of data against a given one
+  static bool validCRC(const uint8_t *data, uint16_t len, uint16_t CRC);
+
+// validCRC #1: check the CRC in a message for validity
+  static bool validCRC(ModbusMessage msg);
+
+// validCRC #2: check the CRC of a message against a given one
+  static bool validCRC(ModbusMessage msg, uint16_t CRC);
+
+// addCRC: extend a RTUMessage by a valid CRC
+  static void addCRC(ModbusMessage& raw);
+
+// calculateInterval: determine the minimal gap time between messages
+  static uint32_t calculateInterval(uint32_t baudRate);
+
+// RTSauto: dummy callback for auto half duplex RS485 boards
+  inline static void RTSauto(bool level) { return; } // NOLINT
+
+// Necessary preparations for a HardwareSerial
+static void prepareHardwareSerial(HardwareSerial& s, uint16_t bufferSize = 260) {
+  s.setRxBufferSize(bufferSize);
+  s.setTxBufferSize(bufferSize);
+}
+
+protected:
+// Printable characters for ASCII protocol: 012345678ABCDEF
+  static const char ASCIIwrite[];
+  static const char ASCIIread[];
+
+  RTUutils() = delete;
+
+// receive: get a Modbus message from serial, maintaining timeouts etc.
+  static ModbusMessage receive(uint8_t caller, Stream& serial, uint32_t timeout, unsigned long& lastMicros, uint32_t interval, bool ASCIImode, bool skipLeadingZeroBytes = false);
+
+// send: send a Modbus message in either format (ModbusMessage or data/len)
+  static void send(Stream& serial, unsigned long& lastMicros, uint32_t interval, RTScallback r, const uint8_t *data, uint16_t len, bool ASCIImode);
+  static void send(Stream& serial, unsigned long& lastMicros, uint32_t interval, RTScallback r, ModbusMessage raw, bool ASCIImode);
+};
+
+#endif
diff --git a/lib/eModbus/src/options.h b/lib/eModbus/src/options.h
new file mode 100644
index 000000000..c65bc1c2b
--- /dev/null
+++ b/lib/eModbus/src/options.h
@@ -0,0 +1,61 @@
+// =================================================================================================
+// eModbus: Copyright 2020 by Michael Harwerth, Bert Melis and the contributors to eModbus
+//               MIT license - see license.md for details
+// =================================================================================================
+#ifndef _EMODBUS_OPTIONS_H
+#define _EMODBUS_OPTIONS_H
+
+/* === ESP32 DEFINITIONS AND MACROS === */
+#if defined(ESP32) 
+#include <Arduino.h>
+#define USE_MUTEX 1
+#define HAS_FREERTOS 1
+#define HAS_ETHERNET 1
+#define IS_LINUX 0
+#define NEED_UART_PATCH 1
+const unsigned int SERVER_TASK_STACK = 4096;
+const unsigned int CLIENT_TASK_STACK = 4096;
+
+/* === ESP8266 DEFINITIONS AND MACROS === */
+#elif defined(ESP8266)
+#include <Arduino.h>
+#define USE_MUTEX 0
+#define HAS_FREERTOS 0
+#define HAS_ETHERNET 0
+#define IS_LINUX 0
+#define NEED_UART_PATCH 0
+
+/* === LINUX DEFINITIONS AND MACROS === */
+#elif defined(__linux__)
+#define USE_MUTEX 1
+#define HAS_FREERTOS 0
+#define HAS_ETHERNET 0
+#define IS_LINUX 1
+#define NEED_UART_PATCH 0
+#include <cstdio>  // for printf()
+#include <cstring> // for memcpy(), strlen() etc.
+#include <cinttypes> // for uint32_t etc.
+#if IS_RASPBERRY
+#include <wiringPi.h>
+#else
+#include <chrono>  // NOLINT
+// Use nanosleep() to avoid problems with pthreads (std::this_thread::sleep_for would interfere!)
+#define delay(x)  nanosleep((const struct timespec[]){{x/1000, (x%1000)*1000000L}}, NULL);
+typedef std::chrono::steady_clock clk;
+#define millis() std::chrono::duration_cast<std::chrono::milliseconds>(clk::now().time_since_epoch()).count()
+#define micros() std::chrono::duration_cast<std::chrono::microseconds>(clk::now().time_since_epoch()).count()
+#endif
+
+/* === INVALID TARGET === */
+#else
+#error Define target in options.h
+#endif
+
+/* === COMMON MACROS === */
+#if USE_MUTEX
+#define LOCK_GUARD(x,y) std::lock_guard<std::mutex> x(y);
+#else
+#define LOCK_GUARD(x,y)
+#endif
+
+#endif // _EMODBUS_OPTIONS_H
diff --git a/scripts/generate-modbus-register-doc.py b/scripts/generate-modbus-register-doc.py
new file mode 100644
index 000000000..b43ef0c79
--- /dev/null
+++ b/scripts/generate-modbus-register-doc.py
@@ -0,0 +1,118 @@
+import fileinput
+import csv
+import sys
+from itertools import groupby
+
+# static data
+
+tag_to_tagtype = {
+    -1: "TAG_TYPE_NONE",
+    0: "DEVICE_DATA",
+    1: "HC",
+    2: "HC",
+    3: "HC",
+    4: "HC",
+    5: "HC",
+    6: "HC",
+    7: "HC",
+    8: "HC",
+    9: "DHW",
+    10: "DHW",
+    11: "DHW",
+    12: "DHW",
+    13: "DHW",
+    14: "DHW",
+    15: "DHW",
+    16: "DHW",
+    17: "DHW",
+    18: "DHW",
+    19: "AHS",
+    20: "HS",
+    21: "HS",
+    22: "HS",
+    23: "HS",
+    24: "HS",
+    25: "HS",
+    26: "HS",
+    27: "HS",
+    28: "HS",
+    29: "HS",
+    30: "HS",
+    31: "HS",
+    32: "HS",
+    33: "HS",
+    34: "HS",
+    35: "HS"
+}
+
+# read entities csv from stdin
+
+entities = []
+
+with fileinput.input() as f_input:
+    entities_reader = csv.reader(f_input, delimiter=',', quotechar='"')
+    headers = next(entities_reader)
+
+    for row in entities_reader:
+        entity = {}
+        for i, val in enumerate(row):
+            entity[headers[i]] = val
+        entities.append(entity)
+
+def device_name_key(e): return e["device name"]
+
+
+def device_type_key(e): return e["device type"]
+
+
+def grouped_by(list, key): return groupby(sorted(list, key=key), key)
+
+
+# entities_by_device_type = grouped_by(entities, device_type_key)
+
+
+def printDeviceEntities(device_name, device_entities):
+    print("### " + device_name)
+    print("| shortname | fullname | type | uom | writeable | tag type | register offset | register count | scale factor |")
+    print("|-|-|-|-|-|-|-|-|-|")
+    for de in device_entities:
+        print("| " + de["shortname"] + " | " + de["fullname"] + " | " + de["type [options...] \\| (min/max)"] + " | " + de["uom"] + " | " + de["writeable"] +
+              " | " + tag_to_tagtype[int(de["modbus block"])] + " | " + de["modbus offset"] + " | " + de["modbus count"] + " | " + de["modbus scale factor"] + " | ")
+    print()
+
+
+def printDeviceTypeDevices(device_type, devices):
+    print("## Devices of type *" + device_type + "*")
+    for device_name, device_entities in grouped_by(devices, device_name_key):
+        printDeviceEntities(device_name, device_entities)
+
+
+# write header
+
+print("<!-- Use full browser width for this page, the tables are wide -->")
+print("<style>")
+print(".md-grid {")
+print("    max-width: 100%; /* or 100%, if you want to stretch to full-width */")
+print("}")
+print("</style>")
+print()
+print("# Entity/Register Mapping")
+print()
+print("!!! note")
+print()
+print("    This file has been auto-generated. Do not edit.")
+print()
+
+for device_type, devices in grouped_by(entities, device_type_key):
+    printDeviceTypeDevices(device_type, devices)
+
+# def printGroupedData(groupedData):
+#    for k, v in groupedData:
+#        # print("Group {} {}".format(k, list(v)))
+#        print(k)
+
+
+# printGroupedData(grouped_entities)
+
+# for e in entities:
+#     print(e)
diff --git a/scripts/generate-modbus-register-doc.sh b/scripts/generate-modbus-register-doc.sh
new file mode 100644
index 000000000..6f1142da9
--- /dev/null
+++ b/scripts/generate-modbus-register-doc.sh
@@ -0,0 +1,6 @@
+#!/bin/bash
+
+make clean
+make ARGS=-DEMSESP_STANDALONE
+echo "test entity_dump" | ./emsesp | python3 ./scripts/strip_csv.py | python3 ./scripts/generate-modbus-register-doc.py
+
diff --git a/scripts/update_modbus_registers.py b/scripts/update_modbus_registers.py
new file mode 100644
index 000000000..b77d14615
--- /dev/null
+++ b/scripts/update_modbus_registers.py
@@ -0,0 +1,256 @@
+#
+# Update modbus parameters from entity definitions.
+# This script generates c++ code for the modbus parameter definitions.
+#
+# Usage:
+# - first, dump all entities to csv by running 'scripts/dump_entities.sh'
+# - then run 'cat ../dump_entities.csv | python3 update_modbus_registers.py > ../src/modbus_entity_parameters.hpp'
+#   from the "scripts" folder
+
+import fileinput
+import csv
+import json
+import re
+from string import Template
+
+modbus_block_size = 1000  # block size of a register block for each tag
+
+# string sizes including terminating NUL. Extracted from the source code.
+string_sizes = {
+    "boiler/lastcode": 55,
+    "boiler/servicecode": 4,
+    "boiler/maintenancemessage": 4,
+    "boiler/maintenancedate": 12,
+    "boiler/hpin1opt": 16,
+    "boiler/hpin2opt": 16,
+    "boiler/hpin3opt": 16,
+    "boiler/hpin4opt": 16,
+    "thermostat/errorcode": 16,
+    "thermostat/lastcode": 50,
+    "thermostat/datetime": 25,
+    "thermostat/wwswitchtime": 16,
+    "thermostat/wwcircswitchtime": 16,
+    "thermostat/circswitchtime": 16,
+    "thermostat/wwholidays": 26,
+    "thermostat/wwvacations": 26,
+    "thermostat/vacations1": 22,
+    "thermostat/vacations2": 22,
+    "thermostat/vacations3": 22,
+    "thermostat/vacations4": 22,
+    "thermostat/vacations5": 22,
+    "thermostat/vacations6": 22,
+    "thermostat/vacations7": 22,
+    "thermostat/holidays": 26,
+    "thermostat/vacations": 26,
+    "thermostat/switchtime1": 16,
+    "thermostat/switchtime2": 16,
+    "thermostat/switchtime": 16,
+    "controller/datetime": 25
+}
+
+tag_to_tagtype = {
+    -1: "TAG_TYPE_NONE",
+    0: "TAG_TYPE_DEVICE_DATA",
+    1: "TAG_TYPE_HC",
+    2: "TAG_TYPE_HC",
+    3: "TAG_TYPE_HC",
+    4: "TAG_TYPE_HC",
+    5: "TAG_TYPE_HC",
+    6: "TAG_TYPE_HC",
+    7: "TAG_TYPE_HC",
+    8: "TAG_TYPE_HC",
+    9: "TAG_TYPE_DHW",
+    10: "TAG_TYPE_DHW",
+    11: "TAG_TYPE_DHW",
+    12: "TAG_TYPE_DHW",
+    13: "TAG_TYPE_DHW",
+    14: "TAG_TYPE_DHW",
+    15: "TAG_TYPE_DHW",
+    16: "TAG_TYPE_DHW",
+    17: "TAG_TYPE_DHW",
+    18: "TAG_TYPE_DHW",
+    19: "TAG_TYPE_AHS",
+    20: "TAG_TYPE_HS",
+    21: "TAG_TYPE_HS",
+    22: "TAG_TYPE_HS",
+    23: "TAG_TYPE_HS",
+    24: "TAG_TYPE_HS",
+    25: "TAG_TYPE_HS",
+    26: "TAG_TYPE_HS",
+    27: "TAG_TYPE_HS",
+    28: "TAG_TYPE_HS",
+    29: "TAG_TYPE_HS",
+    30: "TAG_TYPE_HS",
+    31: "TAG_TYPE_HS",
+    32: "TAG_TYPE_HS",
+    33: "TAG_TYPE_HS",
+    34: "TAG_TYPE_HS",
+    35: "TAG_TYPE_HS"
+}
+
+device_type_names = [
+    "SYSTEM",
+    "TEMPERATURESENSOR",
+    "ANALOGSENSOR",
+    "SCHEDULER",
+    "CUSTOM",
+    "BOILER",
+    "THERMOSTAT",
+    "MIXER",
+    "SOLAR",
+    "HEATPUMP",
+    "GATEWAY",
+    "SWITCH",
+    "CONTROLLER",
+    "CONNECT",
+    "ALERT",
+    "EXTENSION",
+    "GENERIC",
+    "HEATSOURCE",
+    "VENTILATION",
+    "WATER"
+]
+
+cpp_file_template = Template('''#include "modbus.h"
+#include "emsdevice.h"
+
+namespace emsesp {
+
+using dt = EMSdevice::DeviceType;
+
+#define REGISTER_MAPPING(device_type, device_value_tag_type, long_name, modbus_register_offset, modbus_register_count) \\
+    { device_type, device_value_tag_type, long_name[0], modbus_register_offset, modbus_register_count }
+    
+// IMPORTANT: This list MUST be ordered by keys "device_type", "device_value_tag_type" and "modbus_register_offset" in this order.    
+const std::initializer_list<Modbus::EntityModbusInfo> Modbus::modbus_register_mappings = {
+$entries};
+
+} // namespace emsesp''')
+# cpp_entry_template = Template(
+#    '    {std::make_tuple($devtype, $tagtype, std::string(\"$shortname\")), {$registeroffset, $registercount}},\n')
+cpp_entry_template = Template(
+    '    REGISTER_MAPPING($devtype, $tagtype, $shortname, $registeroffset, $registercount), // $entity_name\n')
+
+# read translations
+listNames = {}
+transre = re.compile(r'^MAKE_TRANSLATION\(([^,\s]+)\s*,\s*\"([^\"]+)\"')
+transf = open('./src/locale_translations.h', 'r')
+while True:
+    line = transf.readline()
+    if not line:
+        break
+    m = transre.match(line)
+    if m is not None:
+        listNames[m.group(2)] = m.group(1)
+transf.close()
+
+entities = []
+
+with fileinput.input() as f_input:
+    entities_reader = csv.reader(f_input, delimiter=',', quotechar='"')
+    headers = next(entities_reader)
+
+    for row in entities_reader:
+        entity = {}
+        for i, val in enumerate(row):
+            entity[headers[i]] = val
+        entities.append(entity)
+
+# print(json.dumps(entities, indent="  "))
+
+device_types = {}
+string_entities = []
+
+entity_modbus_property_names = [
+    "modbus block",
+    "modbus offset",
+    "modbus count"
+]
+
+for entity in entities:
+    device_type_name = entity['device type'].upper()
+    if device_type_name not in device_types:
+        device_types[device_type_name] = {}
+    device_type = device_types[device_type_name]
+    tag_name = entity['modbus block']
+    if tag_name not in device_type:
+        device_type[tag_name] = {}
+    tag = device_type[tag_name]
+    entity_shortname = entity['shortname']
+    entity_dev_name = (device_type_name + "/" + entity_shortname).lower()
+
+    # set size for string entities
+    if entity["modbus count"] == "0" and entity_dev_name in string_sizes:
+        entity["modbus count"] = -(-string_sizes[entity_dev_name] // 2)  # divide and round up
+
+    if int(entity["modbus count"]) <= 0:
+        raise Exception('Entity "' + entity_shortname + '" does not have a size - string sizes need to be added manually to update_modbus_registers.py')
+
+    #    if entity["modbus count"] == "0":
+    #        print("ignoring " + entity_dev_name + " - it has a register length of zero")
+
+    if entity_shortname in tag:
+        for entity_property_name in entity_modbus_property_names:
+            if tag[entity_shortname][entity_property_name] != entity[entity_property_name]:
+                raise Exception(
+                    "Property mismatch between instances of the same entity for property '" + entity_property_name + "':\n" +
+                    json.dumps(tag[entity_shortname]) +
+                    json.dumps(entity))
+    else:
+        tag[entity_shortname] = {}
+        for entity_property_name in entity_modbus_property_names:
+            tag[entity_shortname][entity_property_name] = entity[entity_property_name]
+
+# print(json.dumps(device_types, indent="  "))
+
+# ASSIGN REGISTERS
+
+for device_type_name, device_type in device_types.items():
+    for tag, entities in device_type.items():
+        total_registers = 0
+        next_free_offset = 0
+        for entity_name, modbus_info in entities.items():
+            register_offset = int(modbus_info['modbus offset'])
+            register_count = int(modbus_info['modbus count'])
+            total_registers += register_count
+            if register_offset >= 0 and register_offset + register_count > next_free_offset:
+                next_free_offset = register_offset + register_count
+
+        # print(device_type_name + "/" + tag + ": total_registers=" + str(total_registers) + "; next_free_offset=" + str(
+        #    next_free_offset))
+
+        for entity_name, modbus_info in entities.items():
+            register_offset = int(modbus_info['modbus offset'])
+            register_count = int(modbus_info['modbus count'])
+            if register_offset < 0 and register_count > 0:
+                # assign register
+                # print("assign " + entity_name + " -> " + str(next_free_offset))
+                modbus_info['modbus offset'] = str(next_free_offset)
+                next_free_offset += register_count
+
+# OUTPUT
+
+cpp_entries = ""
+
+# traverse all elements in correct order so they are correctly sorted
+for device_type_name in device_type_names:
+    if device_type_name in device_types:
+        device_type = device_types[device_type_name]
+        for ntag in range(0, 40):
+            tag = str(ntag)
+            if tag in device_type:
+                entities = device_type[tag]
+                for entity_name, modbus_info in sorted(entities.items(), key=lambda x: int(x[1]["modbus offset"])):
+                    params = {
+                        'devtype': "dt::" + device_type_name,
+                        "tagtype": tag_to_tagtype[int(tag)],  # re.sub(r"[0-9]+", "*", tag),
+                        "shortname": 'FL_(' + listNames[entity_name] + ")",
+                        "entity_name": entity_name,
+                        'registeroffset': modbus_info["modbus offset"],
+                        'registercount': modbus_info["modbus count"]
+                    }
+                    # print(entitypath + ": " + str(modbus_info))
+                    cpp_entries += cpp_entry_template.substitute(params)
+
+cpp_src = cpp_file_template.substitute({'entries': cpp_entries})
+print(cpp_src)
diff --git a/scripts/update_modbus_registers.sh b/scripts/update_modbus_registers.sh
new file mode 100644
index 000000000..27997ff2e
--- /dev/null
+++ b/scripts/update_modbus_registers.sh
@@ -0,0 +1,55 @@
+#!/bin/bash
+
+# Update modbus parameters from entity definitions.
+# This script generates c++ code for the modbus parameter definitions.
+#
+# Run this script from the EMS-ESP32 root directory with the command `scripts/update_modbus_registers.sh`.
+
+while [[ $# -gt 0 ]]; do
+  case $1 in
+    --reset)
+      RESET=YES
+      shift
+      ;;
+    --force)
+      FORCE=YES
+      shift
+      ;;
+    *|-*|--*)
+      echo "Unknown option $1"
+      exit 1
+      ;;
+  esac
+done
+
+if [ "$RESET" = "YES" ]; then
+  if [ "$FORCE" != "YES" ]; then
+    read -p  "Are you sure you want to reset all modbus entity parameters, potentially generating new register mappings? WARNING: This might introduce breaking changes for end users. [yes/no] " CONFIRMATION
+    if [ "$CONFIRMATION" != "yes" ]; then
+      echo "Aborted."
+      exit 1
+    fi
+  fi
+  echo "Resetting modbus configuration"
+  cat >./src/modbus_entity_parameters.hpp <<EOL
+#include "modbus.h"
+#include "emsdevice.h"
+
+namespace emsesp {
+
+using dt = EMSdevice::DeviceType;
+
+#define REGISTER_MAPPING(device_type, device_value_tag_type, long_name, modbus_register_offset, modbus_register_count) \\
+    { device_type, device_value_tag_type, long_name[0], modbus_register_offset, modbus_register_count }
+
+// IMPORTANT: This list MUST be ordered by keys "device_type", "device_value_tag_type" and "modbus_register_offset" in this order.
+const std::initializer_list<Modbus::EntityModbusInfo> Modbus::modbus_register_mappings = {};
+
+} // namespace emsesp
+EOL
+fi
+
+make clean
+make ARGS=-DEMSESP_STANDALONE
+echo "test entity_dump" | ./emsesp | python3 ./scripts/strip_csv.py | python3 ./scripts/update_modbus_registers.py > ./src/modbus_entity_parameters.hpp
+echo "Modbus entity parameters written to ./src/modbus_entity_parameters.hpp."
diff --git a/src/default_settings.h b/src/default_settings.h
index cfff9bf39..41e6d12a4 100644
--- a/src/default_settings.h
+++ b/src/default_settings.h
@@ -121,6 +121,22 @@
 #define EMSESP_DEFAULT_TELNET_ENABLED true
 #endif
 
+#ifndef EMSESP_DEFAULT_MODBUS_ENABLED
+#define EMSESP_DEFAULT_MODBUS_ENABLED false
+#endif
+
+#ifndef EMSESP_DEFAULT_MODBUS_PORT
+#define EMSESP_DEFAULT_MODBUS_PORT 502
+#endif
+
+#ifndef EMSESP_DEFAULT_MODBUS_MAX_CLIENTS
+#define EMSESP_DEFAULT_MODBUS_MAX_CLIENTS 10
+#endif
+
+#ifndef EMSESP_DEFAULT_MODBUS_TIMEOUT
+#define EMSESP_DEFAULT_MODBUS_TIMEOUT 10000
+#endif
+
 #ifndef EMSESP_DEFAULT_BOARD_PROFILE
 #define EMSESP_DEFAULT_BOARD_PROFILE "default"
 #endif
diff --git a/src/emsdevice.cpp b/src/emsdevice.cpp
index 6b860428f..0175d5bba 100644
--- a/src/emsdevice.cpp
+++ b/src/emsdevice.cpp
@@ -1374,6 +1374,33 @@ void EMSdevice::dump_value_info() {
                 Serial.print(entityid);
             }
 
+            Serial.print(",");
+
+            // modbus specific infos
+
+
+            Serial.print(device_type());
+            Serial.print(',');
+
+            Serial.print(dv.tag);
+            Serial.print(',');
+
+            // numeric operator -> scale factor
+            if (dv.numeric_operator == 0)
+                Serial.print("1");
+            else if (dv.numeric_operator > 0)
+                Serial.printf("1/%d", dv.numeric_operator);
+            else
+                Serial.print(-dv.numeric_operator);
+            Serial.print(",");
+
+            Serial.printf("%d", EMSESP::modbus_->getRegisterOffset(dv));
+            Serial.print(",");
+
+            Serial.printf("%d", EMSESP::modbus_->getRegisterCount(dv));
+
+            // /modbus specific infos
+
             Serial.println();
         }
     }
@@ -1901,4 +1928,155 @@ std::string EMSdevice::name() {
     return custom_name_;
 }
 
+// copy a raw value (i.e. without applying the numeric_operator) to the output buffer.
+// returns true on success.
+int EMSdevice::get_modbus_value(uint8_t tag, const std::string & shortname, std::vector<uint16_t> & result) {
+    // find device value by shortname
+    // TODO linear search is inefficient
+    const auto & it = std::find_if(devicevalues_.begin(), devicevalues_.end(), [&](const DeviceValue & x) { return x.tag == tag && x.short_name == shortname; });
+    if (it == devicevalues_.end())
+        return -1;
+
+    auto & dv = *it;
+
+    // check if it exists, there is a value for the entity. Set the flag to ACTIVE
+    // not that this will override any previously removed states
+    (dv.hasValue()) ? dv.add_state(DeviceValueState::DV_ACTIVE) : dv.remove_state(DeviceValueState::DV_ACTIVE);
+
+    if (!dv.has_state(DeviceValueState::DV_ACTIVE))
+        return -2;
+
+    // handle Booleans
+    if (dv.type == DeviceValueType::BOOL) {
+        if (result.size() != 1)
+            return -3;
+        auto value_bool = *(uint8_t *)(dv.value_p);
+        if (!Helpers::hasValue(value_bool, EMS_VALUE_BOOL))
+            return -4;
+        result[0] = value_bool ? 1 : 0;
+    }
+
+    // handle TEXT strings
+    else if (dv.type == DeviceValueType::STRING) {
+        auto   value_s           = (char *)dv.value_p;
+        size_t length_s          = strlen(value_s) + 1; // length including terminating zero in bytes
+        size_t register_length_s = (length_s + 1) / 2;  // length including terminating zero in uint16_t-registers
+
+        if ((long)result.size() < (long)register_length_s) {
+            return -5;
+        }
+
+        for (auto i = 0; i < register_length_s; i++) {
+            auto hi   = (uint8_t)value_s[2 * i];
+            auto lo   = (uint8_t)(2 * i + 1 < length_s ? value_s[2 * i + 1] : 0);
+            result[i] = ((uint16_t)hi << 8) | lo;
+        }
+    }
+
+    // handle ENUMs
+    else if (dv.type == DeviceValueType::ENUM) {
+        if (result.size() != 1)
+            return -6;
+        auto value_enum = *(uint8_t *)(dv.value_p);
+        if (value_enum >= dv.options_size)
+            return -7;
+        result[0] = (uint16_t)value_enum;
+    }
+
+    // handle Numbers
+    else if (dv.type == DeviceValueType::INT8) {
+        if (result.size() != 1)
+            return -8;
+        result[0] = (uint16_t)(uint8_t)(*(int8_t *)(dv.value_p));
+    } else if (dv.type == DeviceValueType::UINT8) {
+        if (result.size() != 1)
+            return -9;
+        result[0] = (uint16_t)(*(uint8_t *)(dv.value_p));
+    } else if (dv.type == DeviceValueType::INT16) {
+        if (result.size() != 1)
+            return -10;
+        result[0] = (uint16_t)(*(int16_t *)(dv.value_p));
+    } else if (dv.type == DeviceValueType::UINT16) {
+        if (result.size() != 1)
+            return -11;
+        result[0] = *(uint16_t *)(dv.value_p);
+    } else if (dv.type == DeviceValueType::UINT24 || dv.type == DeviceValueType::UINT32 || dv.type == DeviceValueType::TIME) {
+        if (result.size() != 2)
+            return -12;
+        auto value_uint32 = *(uint32_t *)(dv.value_p);
+        result[0]         = (uint16_t)(value_uint32 >> 16);
+        result[1]         = (uint16_t)(value_uint32 & 0xffff);
+    }
+
+    else {
+        return -13;
+    }
+
+    return 0;
+}
+
+bool EMSdevice::modbus_value_to_json(uint8_t tag, const std::string & shortname, const std::vector<uint8_t> & modbus_data, JsonObject & jsonValue) {
+    //Serial.printf("modbus_value_to_json(%d,%s,[%d bytes])\n", tag, shortname.c_str(), modbus_data.size());
+
+    // find device value by shortname
+    const auto & it = std::find_if(devicevalues_.begin(), devicevalues_.end(), [&](const DeviceValue & x) { return x.tag == tag && x.short_name == shortname; });
+    if (it == devicevalues_.end()) {
+        return false;
+    }
+
+    auto & dv = *it;
+
+    // handle Booleans
+    if (dv.type == DeviceValueType::BOOL) {
+        // bools are 1 16 bit register
+        if (modbus_data.size() != 2) {
+            return false;
+        }
+        jsonValue["value"] = modbus_data[0] || modbus_data[1];
+    }
+
+    // handle TEXT strings
+    else if (dv.type == DeviceValueType::STRING) {
+        // text is optionally nul terminated
+        // check if the data contains a null char
+        auto nul_or_end    = std::find(modbus_data.begin(), modbus_data.end(), 0);
+        jsonValue["value"] = std::string(modbus_data.begin(), nul_or_end);
+    }
+
+    // handle ENUMs
+    else if (dv.type == DeviceValueType::ENUM) {
+        // these data types are 1 16 bit register
+        if (modbus_data.size() != 2) {
+            return false;
+        }
+
+        jsonValue["value"] = (uint16_t)modbus_data[0] << 8 | (uint16_t)modbus_data[1];
+    }
+
+    // handle Numbers
+    else if (dv.type == DeviceValueType::INT8 || dv.type == DeviceValueType::UINT8 || dv.type == DeviceValueType::INT16 || dv.type == DeviceValueType::UINT16) {
+        // these data types are 1 16 bit register
+        if (modbus_data.size() != 2) {
+            return false;
+        }
+
+        jsonValue["value"] = Helpers::numericoperator2scalefactor(dv.numeric_operator) * (float)((uint16_t)modbus_data[0] << 8 | (uint16_t)modbus_data[1]);
+    } else if (dv.type == DeviceValueType::UINT24 || dv.type == DeviceValueType::UINT32 || dv.type == DeviceValueType::TIME) {
+        // these data types are 2 16 bit register
+        if (modbus_data.size() != 4) {
+            return false;
+        }
+
+        jsonValue["value"] =
+            Helpers::numericoperator2scalefactor(dv.numeric_operator)
+            * (float)((uint32_t)modbus_data[0] << 24 | (uint32_t)modbus_data[1] << 16 | (uint32_t)modbus_data[2] << 8 | (uint32_t)modbus_data[3]);
+    }
+
+    else {
+        return false;
+    }
+
+    return true;
+}
+
 } // namespace emsesp
diff --git a/src/emsdevice.h b/src/emsdevice.h
index f899f8ee5..64d819ccb 100644
--- a/src/emsdevice.h
+++ b/src/emsdevice.h
@@ -202,6 +202,9 @@ class EMSdevice {
         }
     }
 
+    int  get_modbus_value(uint8_t tag, const std::string & shortname, std::vector<uint16_t> & result);
+    bool modbus_value_to_json(uint8_t tag, const std::string & shortname, const std::vector<uint8_t> & modbus_data, JsonObject & jsonValue);
+
     const char *      brand_to_char();
     const std::string to_string();
     const std::string to_string_short();
diff --git a/src/emsesp.cpp b/src/emsesp.cpp
index e39be2a0d..d99c7d7d1 100644
--- a/src/emsesp.cpp
+++ b/src/emsesp.cpp
@@ -72,6 +72,7 @@ uuid::syslog::SyslogService System::syslog_;
 RxService         EMSESP::rxservice_;         // incoming Telegram Rx handler
 TxService         EMSESP::txservice_;         // outgoing Telegram Tx handler
 Mqtt              EMSESP::mqtt_;              // mqtt handler
+Modbus *          EMSESP::modbus_;            // modbus handler
 System            EMSESP::system_;            // core system services
 TemperatureSensor EMSESP::temperaturesensor_; // Temperature sensors
 AnalogSensor      EMSESP::analogsensor_;      // Analog sensors
@@ -334,8 +335,8 @@ void EMSESP::show_ems(uuid::console::Shell & shell) {
 void EMSESP::dump_all_values(uuid::console::Shell & shell) {
     Serial.println("---- CSV START ----"); // marker use by py script
     // add header for CSV
-    Serial.println(
-        "device name,device type,product id,shortname,fullname,type [options...] \\| (min/max),uom,writeable,discovery entityid v3.4, discovery entityid");
+    Serial.println("device name,device type,product id,shortname,fullname,type [options...] \\| (min/max),uom,writeable,discovery entityid v3.4,discovery "
+                   "entityid,modbus unit identifier,modbus block,modbus scale factor,modbus offset,modbus count");
 
     for (const auto & device_class : EMSFactory::device_handlers()) {
         // go through each device type so they are sorted
@@ -1655,6 +1656,11 @@ void EMSESP::start() {
 #endif
     }
 
+    if (system_.modbus_enabled()) {
+        modbus_ = new Modbus;
+        modbus_->start(1, system_.modbus_port(), system_.modbus_max_clients(), system_.modbus_timeout());
+    }
+
     mqtt_.start();              // mqtt init
     system_.start();            // starts commands, led, adc, button, network (sets hostname), syslog & uart
     shower_.start();            // initialize shower timer and shower alert
diff --git a/src/emsesp.h b/src/emsesp.h
index 6acaa1215..f28d4dba9 100644
--- a/src/emsesp.h
+++ b/src/emsesp.h
@@ -56,6 +56,7 @@
 #include "emsfactory.h"
 #include "telegram.h"
 #include "mqtt.h"
+#include "modbus.h"
 #include "system.h"
 #include "temperaturesensor.h"
 #include "analogsensor.h"
@@ -216,6 +217,7 @@ class EMSESP {
 
     // services
     static Mqtt              mqtt_;
+    static Modbus *          modbus_;
     static System            system_;
     static TemperatureSensor temperaturesensor_;
     static AnalogSensor      analogsensor_;
diff --git a/src/helpers.cpp b/src/helpers.cpp
index 1be369668..f1316d313 100644
--- a/src/helpers.cpp
+++ b/src/helpers.cpp
@@ -837,4 +837,13 @@ uint16_t Helpers::string2minutes(const std::string & str) {
     }
 }
 
+float Helpers::numericoperator2scalefactor(uint8_t numeric_operator) {
+    if (numeric_operator == 0)
+        return 1.0f;
+    else if (numeric_operator > 0)
+        return 1.0f / numeric_operator;
+    else
+        return -numeric_operator;
+}
+
 } // namespace emsesp
diff --git a/src/helpers.h b/src/helpers.h
index a31567e84..cbd600f41 100644
--- a/src/helpers.h
+++ b/src/helpers.h
@@ -50,6 +50,7 @@ class Helpers {
     static bool        check_abs(const int32_t i);
     static uint32_t    abs(const int32_t i);
     static uint16_t    string2minutes(const std::string & str);
+    static float       numericoperator2scalefactor(uint8_t numeric_operator);
 
     static float transformNumFloat(float value, const int8_t numeric_operator, const uint8_t fahrenheit = 0);
 
diff --git a/src/locale_common.h b/src/locale_common.h
index 7d906bdd6..787272ffd 100644
--- a/src/locale_common.h
+++ b/src/locale_common.h
@@ -52,6 +52,7 @@ MAKE_WORD(ems)
 MAKE_WORD(devices)
 MAKE_WORD(shower)
 MAKE_WORD(mqtt)
+MAKE_WORD(modbus)
 MAKE_WORD(emsesp)
 MAKE_WORD(connected)
 MAKE_WORD(disconnected)
diff --git a/src/modbus.cpp b/src/modbus.cpp
new file mode 100644
index 000000000..a67c15ba7
--- /dev/null
+++ b/src/modbus.cpp
@@ -0,0 +1,509 @@
+/**
+ * TODO:
+ * - verwendete libs in readme hinzufügen
+ */
+#include "modbus.h"
+#include "modbus_entity_parameters.hpp"
+#include "emsesp.h"
+#include "emsdevice.h"
+
+#include <string>
+#include <sstream>
+#include <iomanip>
+
+namespace emsesp {
+
+#ifdef EMSESP_STANDALONE
+// no eModbus lib in standalone build
+enum FunctionCode : uint8_t { WRITE_HOLD_REGISTER = 0x06, WRITE_MULT_REGISTERS = 0x10 };
+#endif
+
+uuid::log::Logger Modbus::logger_{F_(modbus), uuid::log::Facility::DAEMON};
+
+void Modbus::start(uint8_t systemServerId, uint16_t port, uint8_t max_clients, uint32_t timeout) {
+#ifndef EMSESP_STANDALONE
+    if (!check_parameter_order()) {
+        LOG_ERROR("Unable to enable Modbus - the parameter list order is corrupt. This is a firmware bug.");
+        return;
+    }
+
+    modbusServer_ = new ModbusServerTCPasync();
+    modbusServer_->registerWorker(systemServerId, READ_INPUT_REGISTER, [this](auto && request) { return handleSystemRead(request); });
+
+    for (uint8_t i = EMSdevice::DeviceType::BOILER; i < EMSdevice::DeviceType::UNKNOWN; i++) {
+        if (i != systemServerId) {
+            modbusServer_->registerWorker(i, READ_INPUT_REGISTER, [this](auto && request) { return handleRead(request); });
+            modbusServer_->registerWorker(i, READ_HOLD_REGISTER, [this](auto && request) { return handleRead(request); });
+            modbusServer_->registerWorker(i, WRITE_HOLD_REGISTER, [this](auto && request) { return handleWrite(request); });
+            modbusServer_->registerWorker(i, WRITE_MULT_REGISTERS, [this](auto && request) { return handleWrite(request); });
+        }
+    }
+    modbusServer_->start(port, max_clients, timeout);
+    LOG_INFO("Modbus server with ID %d started on port %d", systemServerId, port);
+#else
+    if (!check_parameter_order()) {
+        LOG_ERROR("Unable to enable Modbus - the parameter list order is corrupt. This is a firmware bug.");
+    }
+    LOG_INFO("Modbus deactivated in standalone build.");
+#endif
+}
+
+// this is currently never called, just for good measure
+void Modbus::stop() {
+#ifndef EMSESP_STANDALONE
+    modbusServer_->stop();
+    delete modbusServer_;
+    modbusServer_ = nullptr;
+#endif
+}
+
+// Check that the Modbus parameters defined in modbus_entity_parameters.cpp are correctly ordered
+bool Modbus::check_parameter_order() {
+    EntityModbusInfo const * prev    = nullptr;
+    bool                     isFirst = true;
+    for (const auto & mi : modbus_register_mappings) {
+        if (isFirst) {
+            isFirst = false;
+        } else if (prev == nullptr || !prev->isLessThan(mi)) {
+            LOG_ERROR("Error in modbus parameters: %s must be listed before %s.", mi.short_name, prev->short_name);
+            return false;
+        }
+        prev = &mi;
+    }
+    return true;
+}
+
+int8_t Modbus::tag_to_type(int8_t tag) {
+    // this coulod even be an array
+    switch (tag) {
+    case DeviceValue::TAG_NONE:
+        return TAG_TYPE_NONE;
+
+    case DeviceValue::TAG_DEVICE_DATA:
+        return TAG_TYPE_DEVICE_DATA;
+
+    case DeviceValue::TAG_HC1:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC2:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC3:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC4:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC5:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC6:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC7:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_HC8:
+        return TAG_TYPE_HC;
+
+    case DeviceValue::TAG_DHW1:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW2:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW3:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW4:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW5:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW6:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW7:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW8:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW9:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_DHW10:
+        return TAG_TYPE_DHW;
+
+    case DeviceValue::TAG_AHS1:
+        return TAG_TYPE_AHS;
+
+    case DeviceValue::TAG_HS1:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS2:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS3:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS4:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS5:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS6:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS7:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS8:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS9:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS10:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS11:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS12:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS13:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS14:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS15:
+        return TAG_TYPE_HS;
+
+    case DeviceValue::TAG_HS16:
+        return TAG_TYPE_HS;
+
+    default:
+        return INVALID_TAG_TYPE;
+    }
+}
+
+/* DEBUG
+template <typename TInputIter>
+std::string make_hex_string(TInputIter first, TInputIter last) {
+    std::ostringstream ss;
+    ss << std::hex << std::setfill('0');
+
+    while (first != last)
+        ss << std::setw(2) << static_cast<int>(*first++);
+
+    return ss.str();
+}
+*/
+
+/**
+ *
+ * @param request
+ * @return
+ */
+ModbusMessage Modbus::handleSystemRead(const ModbusMessage & request) {
+    ModbusMessage response;
+
+    uint16_t start_address = 0;
+    uint16_t num_words     = 0;
+
+    request.get(2, start_address);
+    request.get(4, num_words);
+
+    LOG_DEBUG("Got request for serverId %d, startAddress %d, numWords %d", request.getServerID(), start_address, num_words);
+
+    if (start_address < 1000) {
+        switch (start_address) {
+        case 1:
+            response.add(request.getServerID());
+            response.add(request.getFunctionCode());
+            response.add((uint8_t)2);
+            response.add((uint16_t)EMSESP::emsdevices.size());
+            break;
+
+        default:
+            response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        }
+    } else if (start_address < 1000 + EMSESP::emsdevices.size()) {
+        const auto & dev = EMSESP::emsdevices[start_address - 1000];
+        response.add(request.getServerID());
+        response.add(request.getFunctionCode());
+        response.add((uint8_t)2);
+        response.add(dev->device_type());
+        response.add(dev->device_id());
+    } else {
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+    }
+
+    return response;
+}
+
+ModbusMessage Modbus::handleRead(const ModbusMessage & request) {
+    ModbusMessage response;
+
+    uint8_t  device_type   = request.getServerID(); // the server ID is the same as the device type
+    uint16_t start_address = 0;
+    uint16_t num_words     = 0;
+
+    request.get(2, start_address);
+    request.get(4, num_words);
+
+    LOG_DEBUG("Got read request for serverId %d, startAddress %d, numWords %d", device_type, start_address, num_words);
+
+    // each register block corresponds to a device value tag
+    auto tag      = (uint8_t)(start_address / REGISTER_BLOCK_SIZE);
+    auto tag_type = tag_to_type(tag);
+
+    if (tag_type == INVALID_TAG_TYPE) {
+        // invalid register block, does not correspond to an existing tag
+        LOG_ERROR("invalid register block, does not correspond to an existing tag");
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    auto register_offset = start_address - tag * REGISTER_BLOCK_SIZE;
+
+    const auto & dev_it =
+        std::find_if(EMSESP::emsdevices.begin(), EMSESP::emsdevices.end(), [&](const std::unique_ptr<EMSdevice> & x) { return x->device_type() == device_type; });
+
+    if (dev_it == EMSESP::emsdevices.end()) {
+        // device not found => invalid server ID
+        LOG_ERROR("device with type %d not found => invalid server ID", device_type);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    const auto & dev = *dev_it;
+
+    // binary search in modbus infos
+    auto key = EntityModbusInfoKey(dev->device_type(), tag_type, register_offset);
+
+    const auto & modbusInfo = std::lower_bound(std::begin(modbus_register_mappings),
+                                               std::end(modbus_register_mappings),
+                                               key,
+                                               [](const EntityModbusInfo & a, const EntityModbusInfoKey & b) { return a.isLessThan(b); });
+
+
+    if (modbusInfo == std::end(modbus_register_mappings) || !modbusInfo->equals(key)) {
+        // combination of device_type/tag_type/register_offset does not exist
+        LOG_ERROR("combination of device_type/tag_type/register_offset does not exist");
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    // only reading a single value at a time is supported for now
+    if (num_words != modbusInfo->registerCount) {
+        // number of registers requested does not match actual register count for entity
+        LOG_ERROR("number of registers requested does not match actual register count for entity");
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    auto buf = std::vector<uint16_t>(num_words);
+    if (dev->get_modbus_value(tag, modbusInfo->short_name, buf) == 0) {
+        response.add(request.getServerID());
+        response.add(request.getFunctionCode());
+        response.add((uint8_t)(num_words * 2));
+        for (auto & value : buf)
+            response.add(value);
+    } else {
+        LOG_ERROR("Unable to read raw device value %s for tag=%d", modbusInfo->short_name, (int)tag);
+        response.setError(request.getServerID(), request.getFunctionCode(), SERVER_DEVICE_FAILURE);
+    }
+
+    return response;
+}
+
+ModbusMessage Modbus::handleWrite(const ModbusMessage & request) {
+    ModbusMessage response;
+
+    uint8_t              device_type   = request.getServerID(); // the server ID is the same as the device type
+    uint8_t              function_code = request.getFunctionCode();
+    uint16_t             start_address = 0;
+    uint16_t             num_words     = 0;
+    uint8_t              byte_count    = 0;
+    std::vector<uint8_t> data;
+
+    if (function_code == WRITE_MULT_REGISTERS) {
+        request.get(2, start_address);
+        request.get(4, num_words);
+        request.get(6, byte_count);
+        request.get(7, data, byte_count);
+    } else if (function_code == WRITE_HOLD_REGISTER) {
+        num_words  = 1;
+        byte_count = 2;
+        request.get(2, start_address);
+        request.get(4, data, byte_count);
+    } else {
+        LOG_ERROR("Function code %d is not implemented", function_code);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_FUNCTION);
+        return response;
+    }
+
+    LOG_DEBUG("Got write request for serverId %d, startAddress %d, numWords %d, byteCount %d", device_type, start_address, num_words, byte_count);
+
+    // each register block corresponds to a device value tag
+    auto tag      = (uint8_t)(start_address / REGISTER_BLOCK_SIZE);
+    auto tag_type = tag_to_type(tag);
+
+    if (tag_type == INVALID_TAG_TYPE) {
+        // invalid register block, does not correspond to an existing tag
+        LOG_ERROR("invalid register block (%d), does not correspond to an existing tag", tag);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    auto register_offset = start_address - tag * REGISTER_BLOCK_SIZE;
+
+    const auto & dev_it =
+        std::find_if(EMSESP::emsdevices.begin(), EMSESP::emsdevices.end(), [&](const std::unique_ptr<EMSdevice> & x) { return x->device_type() == device_type; });
+
+    if (dev_it == EMSESP::emsdevices.end()) {
+        // device not found => invalid server ID
+        LOG_ERROR("device_type (%d) not found => invalid server ID", device_type);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    const auto & dev = *dev_it;
+
+    // binary search in modbus infos
+    auto key        = EntityModbusInfoKey(dev->device_type(), tag_type, register_offset);
+    auto modbusInfo = std::lower_bound(std::begin(modbus_register_mappings),
+                                       std::end(modbus_register_mappings),
+                                       key,
+                                       [](const EntityModbusInfo & mi, const EntityModbusInfoKey & k) { return mi.isLessThan(k); });
+
+    if (modbusInfo == std::end(modbus_register_mappings) || !modbusInfo->equals(key)) {
+        // combination of device_type/tag_type/register_offset does not exist
+        LOG_ERROR("combination of device_type (%d)/tag_type (%d)/register_offset (%d) does not exist",
+                  key.device_type,
+                  key.device_value_tag_type,
+                  key.registerOffset);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    // only writing a single value at a time is supported for now
+    if (num_words != modbusInfo->registerCount) {
+        // number of registers requested does not match actual register count for entity
+        LOG_ERROR("number of registers (%d) requested does not match actual register count (%d) for entity", num_words, modbusInfo->registerCount);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    JsonDocument input_doc;
+    JsonObject   input = input_doc.to<JsonObject>();
+
+    if (!dev->modbus_value_to_json(tag, modbusInfo->short_name, data, input)) {
+        // error getting modbus value as json
+        LOG_ERROR("error getting modbus value as json");
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_ADDRESS);
+        return response;
+    }
+
+    std::string path;
+    if (tag < DeviceValueTAG::TAG_HC1) {
+        path = std::string("ems-esp/") + std::string(EMSdevice::device_type_2_device_name(dev->device_type())) + "/" + modbusInfo->short_name;
+    } else {
+        path = std::string("ems-esp/") + std::string(EMSdevice::device_type_2_device_name(dev->device_type())) + "/" + EMSdevice::tag_to_mqtt(tag) + "/"
+               + modbusInfo->short_name;
+    }
+
+    LOG_DEBUG("path: %s\n", path.c_str());
+
+    std::string inputStr;
+    serializeJson(input, inputStr);
+    LOG_DEBUG("input: %s\n", inputStr.c_str());
+
+    JsonDocument output_doc;
+    JsonObject   output      = output_doc.to<JsonObject>();
+    uint8_t      return_code = Command::process(path.c_str(), true, input, output); // modbus is always authenticated
+
+    if (return_code != CommandRet::OK) {
+        char error[100];
+        if (output.size()) {
+            snprintf(error,
+                     sizeof(error),
+                     "Modbus write command failed with error: %s (%s)",
+                     (const char *)output["message"],
+                     Command::return_code_string(return_code).c_str());
+        } else {
+            snprintf(error, sizeof(error), "Modbus write command failed with error code (%s)", Command::return_code_string(return_code).c_str());
+        }
+        LOG_ERROR(error);
+        response.setError(request.getServerID(), request.getFunctionCode(), ILLEGAL_DATA_VALUE);
+    } else {
+        // all good
+        response.add(request.getServerID());
+        response.add(request.getFunctionCode());
+        response.add(start_address);
+        response.add(num_words);
+    }
+
+    return response;
+}
+
+#if defined(EMSESP_STANDALONE)
+// return the relative register start offset for a DeviceValue, i.e. the address within the
+// register block corresponding to the value's tag type.
+int Modbus::getRegisterOffset(const DeviceValue & dv) {
+    auto it = std::find_if(std::begin(modbus_register_mappings), std::end(modbus_register_mappings), [&](const EntityModbusInfo & mi) {
+        return mi.device_type == dv.device_type && mi.device_value_tag_type == tag_to_type(dv.tag) && !strcmp(mi.short_name, dv.short_name);
+    });
+    if (it != std::end(modbus_register_mappings)) {
+        return it->registerOffset;
+    }
+
+    return -1;
+}
+
+// return the number of registers
+int Modbus::getRegisterCount(const DeviceValue & dv) {
+    auto it = std::find_if(std::begin(modbus_register_mappings), std::end(modbus_register_mappings), [&](const EntityModbusInfo & mi) {
+        return mi.device_type == dv.device_type && mi.device_value_tag_type == tag_to_type(dv.tag) && !strcmp(mi.short_name, dv.short_name);
+    });
+    if (it != std::end(modbus_register_mappings)) {
+        // look up actual size
+        return it->registerCount;
+    } else {
+        // guess based on type
+        switch (dv.type) {
+        case DeviceValue::BOOL: // 8 bit
+        case DeviceValue::INT8:
+        case DeviceValue::UINT8:
+        case DeviceValue::INT16:
+        case DeviceValue::UINT16:
+        case DeviceValue::ENUM: // 8 bit
+        case DeviceValue::CMD:
+            return 1;
+
+        case DeviceValue::UINT24:
+        case DeviceValue::UINT32:
+        case DeviceValue::TIME: // 32 bit
+            return 2;
+
+        case DeviceValue::STRING:
+            break; // impossible to guess, needs to be hardcoded
+        }
+    }
+
+    return 0;
+}
+
+// return the absolute register start address for a DeviceValue
+int Modbus::getRegisterStartAddress(const DeviceValue & dv) {
+    return dv.tag * REGISTER_BLOCK_SIZE + getRegisterOffset(dv);
+}
+#endif
+
+} // namespace emsesp
diff --git a/src/modbus.h b/src/modbus.h
new file mode 100644
index 000000000..a5e0ed06d
--- /dev/null
+++ b/src/modbus.h
@@ -0,0 +1,112 @@
+//
+// Created by Michael Heyse on 08.02.24.
+//
+
+#ifndef EMSESP_MODBUS_H_
+#define EMSESP_MODBUS_H_
+
+#include "helpers.h"
+#include "emsdevice.h"
+#include "emsdevicevalue.h"
+
+#include <string>
+#include <map>
+#include <utility>
+
+#if defined(EMSESP_STANDALONE) || defined(EMSESP_TEST)
+
+#include <modbus_test.h>
+
+#endif
+
+#ifndef EMSESP_STANDALONE
+#include <ModbusServerTCPasync.h>
+#endif
+
+namespace emsesp {
+
+class Modbus {
+  public:
+    static const int REGISTER_BLOCK_SIZE = 1000;
+
+    void start(uint8_t systemServerId, uint16_t port, uint8_t max_clients, uint32_t timeout);
+    void stop();
+
+#if defined(EMSESP_STANDALONE)
+    int getRegisterOffset(const DeviceValue & dv);
+    int getRegisterCount(const DeviceValue & dv);
+    int getRegisterStartAddress(const DeviceValue & dv);
+#endif
+
+  private:
+    static uuid::log::Logger logger_;
+
+    struct EntityModbusInfoKey {
+        const uint8_t  device_type;
+        const uint8_t  device_value_tag_type;
+        const uint16_t registerOffset;
+
+        EntityModbusInfoKey(uint8_t deviceType, uint8_t deviceValueTagType, uint16_t registerOffset)
+            : device_type(deviceType)
+            , device_value_tag_type(deviceValueTagType)
+            , registerOffset(registerOffset) {
+        }
+
+        bool equals(const EntityModbusInfoKey & other) const {
+            return device_type == other.device_type && device_value_tag_type == other.device_value_tag_type && registerOffset == other.registerOffset;
+        }
+    };
+
+    struct EntityModbusInfo {
+        const uint8_t      device_type;
+        const uint8_t      device_value_tag_type;
+        const char * const short_name;
+        const uint16_t     registerOffset;
+        const uint16_t     registerCount;
+
+        bool equals(const EntityModbusInfoKey & other) const {
+            return device_type == other.device_type && device_value_tag_type == other.device_value_tag_type && registerOffset == other.registerOffset;
+        }
+
+        bool isLessThan(const EntityModbusInfoKey & other) const {
+            return device_type < other.device_type || ((device_type == other.device_type) && (device_value_tag_type < other.device_value_tag_type))
+                   || ((device_type == other.device_type) && (device_value_tag_type == other.device_value_tag_type) && (registerOffset < other.registerOffset));
+        }
+
+        bool isLessThan(const EntityModbusInfo & other) const {
+            return device_type < other.device_type || ((device_type == other.device_type) && (device_value_tag_type < other.device_value_tag_type))
+                   || ((device_type == other.device_type) && (device_value_tag_type == other.device_value_tag_type) && (registerOffset < other.registerOffset));
+        }
+    };
+
+    enum DeviceValueTAGType : int8_t {
+        TAG_TYPE_NONE        = DeviceValue::DeviceValueTAG::TAG_NONE,
+        TAG_TYPE_DEVICE_DATA = DeviceValue::DeviceValueTAG::TAG_DEVICE_DATA,
+        TAG_TYPE_HC          = DeviceValue::DeviceValueTAG::TAG_HC1,
+        TAG_TYPE_DHW         = DeviceValue::DeviceValueTAG::TAG_DHW1,
+        TAG_TYPE_AHS         = DeviceValue::DeviceValueTAG::TAG_AHS1,
+        TAG_TYPE_HS          = DeviceValue::DeviceValueTAG::TAG_HS1,
+        INVALID_TAG_TYPE     = -2
+    };
+
+    static const std::initializer_list<EntityModbusInfo> modbus_register_mappings;
+
+    static int8_t tag_to_type(int8_t tag);
+    static bool   check_parameter_order();
+
+#ifndef EMSESP_STANDALONE
+    ModbusServerTCPasync * modbusServer_;
+#endif
+
+#if defined(EMSESP_STANDALONE) || defined(EMSESP_TEST)
+  public:
+#endif
+
+    static ModbusMessage handleSystemRead(const ModbusMessage & request);
+    static ModbusMessage handleRead(const ModbusMessage & request);
+    static ModbusMessage handleWrite(const ModbusMessage & request);
+};
+
+} // namespace emsesp
+
+#endif //EMSESP_MODBUS_H_
diff --git a/src/modbus_entity_parameters.hpp b/src/modbus_entity_parameters.hpp
new file mode 100644
index 000000000..0556f8d30
--- /dev/null
+++ b/src/modbus_entity_parameters.hpp
@@ -0,0 +1,515 @@
+#include "modbus.h"
+#include "emsdevice.h"
+
+namespace emsesp {
+
+using dt = EMSdevice::DeviceType;
+
+#define REGISTER_MAPPING(device_type, device_value_tag_type, long_name, modbus_register_offset, modbus_register_count) \
+    { device_type, device_value_tag_type, long_name[0], modbus_register_offset, modbus_register_count }
+    
+// IMPORTANT: This list MUST be ordered by keys "device_type", "device_value_tag_type" and "modbus_register_offset" in this order.    
+const std::initializer_list<Modbus::EntityModbusInfo> Modbus::modbus_register_mappings = {
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(reset), 0, 1), // reset
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(forceHeatingOff), 1, 1), // heatingoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingActive), 2, 1), // heatingactive
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(tapwaterActive), 3, 1), // tapwateractive
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(selFlowTemp), 4, 1), // selflowtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingPumpMod), 5, 1), // heatingpumpmod
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(outdoorTemp), 6, 1), // outdoortemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(curFlowTemp), 7, 1), // curflowtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(retTemp), 8, 1), // rettemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(switchTemp), 9, 1), // switchtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(sysPress), 10, 1), // syspress
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(boilTemp), 11, 1), // boiltemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(headertemp), 12, 1), // headertemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingActivated), 13, 1), // heatingactivated
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingTemp), 14, 1), // heatingtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingPump), 15, 1), // heatingpump
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pumpModMax), 16, 1), // pumpmodmax
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pumpModMin), 17, 1), // pumpmodmin
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pumpMode), 18, 1), // pumpmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pumpCharacter), 19, 1), // pumpcharacter
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pumpDelay), 20, 1), // pumpdelay
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(setFlowTemp), 21, 1), // setflowtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(setBurnPow), 22, 1), // setburnpow
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(selBurnPow), 23, 1), // selburnpow
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(curBurnPow), 24, 1), // curburnpow
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnStarts), 25, 2), // burnstarts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnWorkMin), 27, 2), // burnworkmin
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burn2WorkMin), 29, 2), // burn2workmin
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatWorkMin), 31, 2), // heatworkmin
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatStarts), 33, 2), // heatstarts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(UBAuptime), 35, 2), // ubauptime
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(lastCode), 37, 28), // lastcode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(serviceCode), 65, 2), // servicecode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(serviceCodeNumber), 67, 1), // servicecodenumber
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maintenanceMessage), 68, 2), // maintenancemessage
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maintenanceType), 70, 1), // maintenance
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maintenanceTime), 71, 1), // maintenancetime
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maintenanceDate), 72, 6), // maintenancedate
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(emergencyOps), 78, 1), // emergencyops
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(emergencyTemp), 79, 1), // emergencytemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgTotal), 80, 2), // nrgtotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgHeat), 82, 2), // nrgheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(meterTotal), 84, 2), // metertotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(meterComp), 86, 2), // metercomp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(meterEHeat), 88, 2), // metereheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(meterHeat), 90, 2), // meterheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(upTimeTotal), 92, 2), // uptimetotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(upTimeControl), 94, 2), // uptimecontrol
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(upTimeCompHeating), 96, 2), // uptimecompheating
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(upTimeCompCooling), 98, 2), // uptimecompcooling
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(upTimeCompPool), 100, 2), // uptimecomppool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(totalCompStarts), 102, 2), // totalcompstarts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingStarts), 104, 2), // heatingstarts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(coolingStarts), 106, 2), // coolingstarts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(poolStarts), 108, 2), // poolstarts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgConsTotal), 110, 2), // nrgconstotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgConsCompTotal), 112, 2), // nrgconscomptotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgConsCompHeating), 114, 2), // nrgconscompheating
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgConsCompCooling), 116, 2), // nrgconscompcooling
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgConsCompPool), 118, 2), // nrgconscomppool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxElecHeatNrgConsTotal), 120, 2), // auxelecheatnrgconstotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxElecHeatNrgConsHeating), 122, 2), // auxelecheatnrgconsheating
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxElecHeatNrgConsPool), 124, 2), // auxelecheatnrgconspool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgSuppTotal), 126, 2), // nrgsupptotal
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgSuppHeating), 128, 2), // nrgsuppheating
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgSuppCooling), 130, 2), // nrgsuppcooling
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgSuppPool), 132, 2), // nrgsupppool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpPower), 134, 1), // hppower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpMaxPower), 135, 1), // hpmaxpower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpSetDiffPress), 136, 1), // hpsetdiffpress
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpCompOn), 137, 1), // hpcompon
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpActivity), 138, 1), // hpactivity
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpBrinePumpSpd), 139, 1), // hpbrinepumpspd
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpSwitchValve), 140, 1), // hpswitchvalve
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpCompSpd), 141, 1), // hpcompspd
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpCircSpd), 142, 1), // hpcircspd
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpBrineIn), 143, 1), // hpbrinein
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpBrineOut), 144, 1), // hpbrineout
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTc0), 145, 1), // hptc0
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTc1), 146, 1), // hptc1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTc3), 147, 1), // hptc3
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTr1), 148, 1), // hptr1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTr3), 149, 1), // hptr3
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTr4), 150, 1), // hptr4
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTr5), 151, 1), // hptr5
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTr6), 152, 1), // hptr6
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTr7), 153, 1), // hptr7
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTl2), 154, 1), // hptl2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpPl1), 155, 1), // hppl1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpPh1), 156, 1), // hpph1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTa4), 157, 1), // hpta4
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpTw1), 158, 1), // hptw1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(poolSetTemp), 159, 1), // poolsettemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hp4wayValve), 160, 1), // hp4way
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpInput1), 161, 1), // hpin1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpIn1Opt), 162, 8), // hpin1opt
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpInput2), 170, 1), // hpin2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpIn2Opt), 171, 8), // hpin2opt
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpInput3), 179, 1), // hpin3
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpIn3Opt), 180, 8), // hpin3opt
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpInput4), 188, 1), // hpin4
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpIn4Opt), 189, 8), // hpin4opt
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maxHeatComp), 197, 1), // maxheatcomp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(maxHeatHeat), 198, 1), // maxheatheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(manDefrost), 199, 1), // mandefrost
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(pvCooling), 200, 1), // pvcooling
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterOnly), 201, 1), // auxheateronly
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterOff), 202, 1), // auxheateroff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterStatus), 203, 1), // auxheaterstatus
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeaterDelay), 204, 1), // auxheaterdelay
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxMaxLimit), 205, 1), // auxmaxlimit
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxLimitStart), 206, 1), // auxlimitstart
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeatMode), 207, 1), // auxheatrmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpHystHeat), 208, 1), // hphystheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpHystCool), 209, 1), // hphystcool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpHystPool), 210, 1), // hphystpool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(silentMode), 211, 1), // silentmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(silentFrom), 212, 1), // silentfrom
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(silentTo), 213, 1), // silentto
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(minTempSilent), 214, 1), // mintempsilent
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(tempParMode), 215, 1), // tempparmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(auxHeatMixValve), 216, 1), // auxheatmix
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(tempDiffHeat), 217, 1), // tempdiffheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(tempDiffCool), 218, 1), // tempdiffcool
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(vp_cooling), 219, 1), // vpcooling
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatCable), 220, 1), // heatcable
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(VC0valve), 221, 1), // vc0valve
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(primePump), 222, 1), // primepump
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(primePumpMod), 223, 1), // primepumpmod
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hp3wayValve), 224, 1), // hp3way
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(elHeatStep1), 225, 1), // elheatstep1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(elHeatStep2), 226, 1), // elheatstep2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(elHeatStep3), 227, 1), // elheatstep3
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpEA0), 228, 1), // hpea0
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpPumpMode), 229, 1), // hppumpmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpFan), 230, 1), // fan
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(hpShutdown), 231, 1), // shutdown
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(exhaustTemp), 232, 1), // exhausttemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnGas), 233, 1), // burngas
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnGas2), 234, 1), // burngas2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(flameCurr), 235, 1), // flamecurr
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(fanWork), 236, 1), // fanwork
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(ignWork), 237, 1), // ignwork
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(oilPreHeat), 238, 1), // oilpreheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnMinPower), 239, 1), // burnminpower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnMaxPower), 240, 1), // burnmaxpower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(burnMinPeriod), 241, 1), // burnminperiod
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(absBurnPow), 242, 1), // absburnpow
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatblock), 243, 1), // heatblock
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(boilHystOn), 244, 1), // boilhyston
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(boilHystOff), 245, 1), // boilhystoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(boil2HystOn), 246, 1), // boil2hyston
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(boil2HystOff), 247, 1), // boil2hystoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(curveOn), 248, 1), // curveon
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(curveBase), 249, 1), // curvebase
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(curveEnd), 250, 1), // curveend
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(summertemp), 251, 1), // summertemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nofrostmode), 252, 1), // nofrostmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nofrosttemp), 253, 1), // nofrosttemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(gasMeterHeat), 254, 2), // gasmeterheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nrgHeat2), 256, 2), // nrgheat2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(nomPower), 258, 1), // nompower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(netFlowTemp), 259, 1), // netflowtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatValve), 260, 1), // heatvalve
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(keepWarmTemp), 261, 1), // keepwarmtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(setReturnTemp), 262, 1), // setreturntemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DEVICE_DATA, FL_(heatingOn), 263, 1), // heating
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(nrgWw), 0, 2), // nrg
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(meterWw), 2, 2), // meter
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(upTimeCompWw), 4, 2), // uptimecomp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwStarts2), 6, 2), // starts2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(nrgConsCompWw), 8, 2), // nrgconscomp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(auxElecHeatNrgConsWw), 10, 2), // auxelecheatnrgcons
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(nrgSuppWw), 12, 2), // nrgsupp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(maxHeatDhw), 14, 1), // maxheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwAlternatingOper), 15, 1), // alternatingop
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwAltOpPrioHeat), 16, 1), // altopprioheat
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwAltOpPrioWw), 17, 1), // altopprio
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwComfOffTemp), 18, 1), // comfoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwEcoOffTemp), 19, 1), // ecooff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwEcoPlusOffTemp), 20, 1), // ecoplusoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwComfDiffTemp), 21, 1), // comfdiff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwEcoDiffTemp), 22, 1), // ecodiff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwEcoPlusDiffTemp), 23, 1), // ecoplusdiff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwComfStopTemp), 24, 1), // comfstop
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwEcoStopTemp), 25, 1), // ecostop
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwEcoPlusStopTemp), 26, 1), // ecoplusstop
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(hpCircPumpWw), 27, 1), // hpcircpump
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwtapactivated), 28, 1), // tapactivated
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSetTemp), 29, 1), // settemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(selRoomTemp), 30, 1), // seltemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSelTempLow), 31, 1), // seltemplow
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSelTempEco), 32, 1), // tempecoplus
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSelTempOff), 33, 1), // seltempoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSelTempSingle), 34, 1), // seltempsingle
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSolarTemp), 35, 1), // solartemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwType), 36, 1), // type
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwComfort), 37, 1), // comfort
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwComfort1), 38, 1), // comfort1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(flowtempoffset), 39, 1), // flowtempoffset
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwChargeOptimization), 40, 1), // chargeoptimization
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwMaxPower), 41, 1), // maxpower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwMaxTemp), 42, 1), // maxtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCircPump), 43, 1), // circpump
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwChargeType), 44, 1), // chargetype
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwHystOn), 45, 1), // hyston
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwHystOff), 46, 1), // hystoff
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwDisinfectionTemp), 47, 1), // disinfectiontemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCircMode), 48, 1), // circmode
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCirc), 49, 1), // circ
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCurTemp), 50, 1), // curtemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCurTemp2), 51, 1), // curtemp2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCurFlow), 52, 1), // curflow
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwStorageTemp1), 53, 1), // storagetemp1
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwStorageTemp2), 54, 1), // storagetemp2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(activated), 55, 1), // activated
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwOneTime), 56, 1), // onetime
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwDisinfecting), 57, 1), // disinfecting
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwCharging), 58, 1), // charging
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwRecharging), 59, 1), // recharging
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwTempOK), 60, 1), // tempok
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwActive), 61, 1), // active
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(ww3wayValve), 62, 1), // 3wayvalve
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwSetPumpPower), 63, 1), // setpumppower
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwMixerTemp), 64, 1), // mixertemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(cylMiddleTemp), 65, 1), // cylmiddletemp
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwStarts), 66, 2), // starts
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwWorkM), 68, 2), // workm
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(gasMeterWw), 70, 2), // gasmeter
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(nrgWw2), 72, 2), // nrg2
+    REGISTER_MAPPING(dt::BOILER, TAG_TYPE_DHW, FL_(wwValve), 74, 1), // dhwvalve
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(errorCode), 0, 8), // errorcode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(lastCode), 8, 25), // lastcode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(dateTime), 33, 13), // datetime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(ibaCalIntTemperature), 46, 1), // intoffset
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(floordrystatus), 47, 1), // floordry
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(dampedoutdoortemp), 48, 1), // dampedoutdoortemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(floordrytemp), 49, 1), // floordrytemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(ibaBuildingType), 50, 1), // building
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(ibaMinExtTemperature), 51, 1), // minexttemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(damping), 52, 1), // damping
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(hybridStrategy), 53, 1), // hybridstrategy
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(switchOverTemp), 54, 1), // switchovertemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(energyCostRatio), 55, 1), // energycostratio
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(fossileFactor), 56, 1), // fossilefactor
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(electricFactor), 57, 1), // electricfactor
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(delayBoiler), 58, 1), // delayboiler
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(tempDiffBoiler), 59, 1), // tempdiffboiler
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(pvEnableWw), 60, 1), // pvenabledhw
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(pvRaiseHeat), 61, 1), // pvraiseheat
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(pvLowerCool), 62, 1), // pvlowercool
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(ibaMainDisplay), 63, 1), // display
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(ibaLanguage), 64, 1), // language
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(ibaClockOffset), 65, 1), // clockoffset
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(tempsensor1), 66, 1), // inttemp1
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(tempsensor2), 67, 1), // inttemp2
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(autodst), 68, 1), // autodst
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(backlight), 69, 1), // backlight
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(brightness), 70, 1), // brightness
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(mixingvalves), 71, 1), // mixingvalves
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(heatingPID), 72, 1), // heatingpid
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(preheating), 73, 1), // preheating
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DEVICE_DATA, FL_(vacations), 74, 13), // vacations
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(selRoomTemp), 0, 1), // seltemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(roomTemp), 1, 1), // currtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(haclimate), 2, 1), // haclimate
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(mode), 3, 1), // mode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(modetype), 4, 1), // modetype
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(ecotemp), 5, 1), // ecotemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(manualtemp), 6, 1), // manualtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(comforttemp), 7, 1), // comforttemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(summertemp), 8, 1), // summertemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(designtemp), 9, 1), // designtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(offsettemp), 10, 1), // offsettemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(minflowtemp), 11, 1), // minflowtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(maxflowtemp), 12, 1), // maxflowtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(roominfluence), 13, 1), // roominfluence
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(roominfl_factor), 14, 1), // roominflfactor
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(curroominfl), 15, 1), // curroominfl
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(nofrostmode), 16, 1), // nofrostmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(nofrosttemp), 17, 1), // nofrosttemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(targetflowtemp), 18, 1), // targetflowtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(heatingtype), 19, 1), // heatingtype
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(summersetmode), 20, 1), // summersetmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(hpoperatingmode), 21, 1), // hpoperatingmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(summermode), 22, 1), // summermode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(hpoperatingstate), 23, 1), // hpoperatingstate
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(controlmode), 24, 1), // controlmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(program), 25, 1), // program
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(tempautotemp), 26, 1), // tempautotemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(remoteseltemp), 27, 1), // remoteseltemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(fastheatup), 28, 1), // fastheatup
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(switchonoptimization), 29, 1), // switchonoptimization
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(reducemode), 30, 1), // reducemode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(noreducetemp), 31, 1), // noreducetemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(reducetemp), 32, 1), // reducetemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(wwprio), 33, 1), // dhwprio
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(hpcooling), 34, 1), // cooling
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(coolingOn), 35, 1), // coolingon
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(hpmode), 36, 1), // hpmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(dewoffset), 37, 1), // dewoffset
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(roomtempdiff), 38, 1), // roomtempdiff
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(hpminflowtemp), 39, 1), // hpminflowtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(control), 40, 1), // control
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(remotetemp), 41, 1), // remotetemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(remotehum), 42, 1), // remotehum
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(heatondelay), 43, 1), // heatondelay
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(heatoffdelay), 44, 1), // heatoffdelay
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(instantstart), 45, 1), // instantstart
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(boost), 46, 1), // boost
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(boosttime), 47, 1), // boosttime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(daytemp), 48, 1), // daytemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(nighttemp2), 49, 1), // nighttemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(holidaytemp), 50, 1), // holidaytemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(holidaymode), 51, 1), // holidaymode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(flowtempoffset), 52, 1), // flowtempoffset
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(holidays), 53, 13), // holidays
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations), 66, 13), // vacations
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(pause), 79, 1), // pause
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(party), 80, 1), // party
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacreducetemp), 81, 1), // vacreducetemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacreducemode), 82, 1), // vacreducemode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(switchtime1), 83, 8), // switchtime1
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(switchtime2), 91, 8), // switchtime2
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(offtemp), 99, 1), // offtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(daylowtemp), 100, 1), // daytemp2
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(daymidtemp), 101, 1), // daytemp3
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(dayhightemp), 102, 1), // daytemp4
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(wwswitchtime), 103, 8), // switchtime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations1), 111, 11), // vacations1
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations2), 122, 11), // vacations2
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations3), 133, 11), // vacations3
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations4), 144, 11), // vacations4
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations5), 155, 11), // vacations5
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations6), 166, 11), // vacations6
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(vacations7), 177, 11), // vacations7
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(reducehours), 188, 1), // reducehours
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(reduceminutes), 189, 1), // reduceminutes
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(heattemp), 190, 1), // heattemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(roomsensor), 191, 1), // roomsensor
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_HC, FL_(heatup), 192, 1), // heatup
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(mode), 0, 1), // mode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwSetTemp), 1, 1), // settemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwSetTempLow), 2, 1), // settemplow
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwCircMode), 3, 1), // circmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwChargeDuration), 4, 1), // chargeduration
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwCharge), 5, 1), // charge
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwExtra), 6, 1), // extra
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwDisinfecting), 7, 1), // disinfecting
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwDisinfectDay), 8, 1), // disinfectday
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwDisinfectTime), 9, 1), // disinfecttime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwDailyHeating), 10, 1), // dailyheating
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwDailyHeatTime), 11, 1), // dailyheattime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwProgMode), 12, 1), // progmode
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwCircProg), 13, 1), // circprog
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwDisinfectHour), 14, 1), // disinfecthour
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwMaxTemp), 15, 1), // maxtemp
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwOneTimeKey), 16, 1), // onetimekey
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwswitchtime), 17, 8), // switchtime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwcircswitchtime), 25, 8), // circswitchtime
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(holidays), 33, 13), // holidays
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(vacations), 46, 13), // vacations
+    REGISTER_MAPPING(dt::THERMOSTAT, TAG_TYPE_DHW, FL_(wwWhenModeOff), 59, 1), // whenmodeoff
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(flowTempHc), 0, 1), // flowtemphc
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(valveStatus), 1, 1), // valvestatus
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(flowSetTemp), 2, 1), // flowsettemp
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(wwPumpStatus), 3, 1), // pumpstatus
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(activated), 4, 1), // activated
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(mixerSetTime), 5, 1), // valvesettime
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(flowTempVf), 6, 1), // flowtempvf
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_HC, FL_(flowtempoffset), 7, 1), // flowtempoffset
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(flowTempHc), 0, 1), // flowtemphc
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(valveStatus), 1, 1), // valvestatus
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(flowSetTemp), 2, 1), // flowsettemp
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(wwPumpStatus), 3, 1), // pumpstatus
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(activated), 4, 1), // activated
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(mixerSetTime), 5, 1), // valvesettime
+    REGISTER_MAPPING(dt::MIXER, TAG_TYPE_DHW, FL_(flowtempoffset), 6, 1), // flowtempoffset
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collectorTemp), 0, 1), // collectortemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cylBottomTemp), 1, 1), // cylbottomtemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPump), 2, 1), // solarpump
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(pumpWorkTime), 3, 2), // pumpworktime
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cylMaxTemp), 5, 1), // cylmaxtemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collectorShutdown), 6, 1), // collectorshutdown
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cylHeated), 7, 1), // cylheated
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPumpMod), 8, 1), // solarpumpmod
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(pumpMinMod), 9, 1), // pumpminmod
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPumpTurnonDiff), 10, 1), // turnondiff
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPumpTurnoffDiff), 11, 1), // turnoffdiff
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPower), 12, 1), // solarpower
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(energyLastHour), 13, 2), // energylasthour
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(maxFlow), 15, 1), // maxflow
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarIsEnabled), 16, 1), // solarenabled
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cylMiddleTemp), 17, 1), // cylmiddletemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(retHeatAssist), 18, 1), // retheatassist
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(m1Valve), 19, 1), // heatassistvalve
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collector2Temp), 20, 1), // collector2temp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(m1Power), 21, 1), // heatassistpower
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPump2), 22, 1), // solarpump2
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPump2Mod), 23, 1), // solarpump2mod
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cyl2BottomTemp), 24, 1), // cyl2bottomtemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(heatExchangerTemp), 25, 1), // heatexchangertemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cylPumpMod), 26, 1), // cylpumpmod
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(valveStatus), 27, 1), // valvestatus
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(vs1Status), 28, 1), // vs1status
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collectorMaxTemp), 29, 1), // collectormaxtemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collectorMinTemp), 30, 1), // collectormintemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(energyToday), 31, 2), // energytoday
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(energyTotal), 33, 2), // energytotal
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(pump2WorkTime), 35, 2), // pump2worktime
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(m1WorkTime), 37, 2), // m1worktime
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(heatTransferSystem), 39, 1), // heattransfersystem
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(externalCyl), 40, 1), // externalcyl
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(thermalDisinfect), 41, 1), // thermaldisinfect
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(heatMetering), 42, 1), // heatmetering
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(activated), 43, 1), // activated
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPumpMode), 44, 1), // solarpumpmode
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPumpKick), 45, 1), // pumpkick
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(plainWaterMode), 46, 1), // plainwatermode
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(doubleMatchFlow), 47, 1), // doublematchflow
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(pump2MinMod), 48, 1), // pump2minmod
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPump2TurnonDiff), 49, 1), // turnondiff2
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPump2TurnoffDiff), 50, 1), // turnoffdiff2
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(solarPump2Kick), 51, 1), // pump2kick
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(climateZone), 52, 1), // climatezone
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collector1Area), 53, 1), // collector1area
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collector1Type), 54, 1), // collector1type
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collector2Area), 55, 1), // collector2area
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(collector2Type), 56, 1), // collector2type
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(cylPriority), 57, 1), // cylpriority
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(heatCntFlowTemp), 58, 1), // heatcntflowtemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(heatCntRetTemp), 59, 1), // heatcntrettemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(heatCnt), 60, 1), // heatcnt
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(swapFlowTemp), 61, 1), // swapflowtemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DEVICE_DATA, FL_(swapRetTemp), 62, 1), // swaprettemp
+    REGISTER_MAPPING(dt::SOLAR, TAG_TYPE_DHW, FL_(wwMinTemp), 0, 1), // mintemp
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(airHumidity), 0, 1), // airhumidity
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(dewTemperature), 1, 1), // dewtemperature
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(curFlowTemp), 2, 1), // curflowtemp
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(retTemp), 3, 1), // rettemp
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(sysRetTemp), 4, 1), // sysrettemp
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTa4), 5, 1), // hpta4
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTr1), 6, 1), // hptr1
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTr3), 7, 1), // hptr3
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTr4), 8, 1), // hptr4
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTr5), 9, 1), // hptr5
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTr6), 10, 1), // hptr6
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpTl2), 11, 1), // hptl2
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpPl1), 12, 1), // hppl1
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpPh1), 13, 1), // hpph1
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(heatingPumpMod), 14, 1), // heatingpumpmod
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hpCompSpd), 15, 1), // hpcompspd
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hybridStrategy), 16, 1), // hybridstrategy
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(lowNoiseMode), 17, 1), // lownoisemode
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(lowNoiseStart), 18, 1), // lownoisestart
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(lowNoiseStop), 19, 1), // lownoisestop
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(hybridDHW), 20, 1), // hybriddhw
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(energyPriceGas), 21, 1), // energypricegas
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(energyPriceEl), 22, 1), // energypriceel
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(energyPricePV), 23, 1), // energyfeedpv
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(switchOverTemp), 24, 1), // switchovertemp
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(airPurgeMode), 25, 1), // airpurgemode
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(heatPumpOutput), 26, 1), // heatpumpoutput
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(coolingCircuit), 27, 1), // coolingcircuit
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(compStartMod), 28, 1), // compstartmod
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(heatDrainPan), 29, 1), // heatdrainpan
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(heatCable), 30, 1), // heatcable
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(nrgTotal), 31, 2), // nrgtotal
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(nrgHeat), 33, 2), // nrgheat
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(meterTotal), 35, 2), // metertotal
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(meterComp), 37, 2), // metercomp
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(meterEHeat), 39, 2), // metereheat
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DEVICE_DATA, FL_(meterHeat), 41, 2), // meterheat
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DHW, FL_(nrgWw), 0, 2), // nrg
+    REGISTER_MAPPING(dt::HEATPUMP, TAG_TYPE_DHW, FL_(meterWw), 2, 2), // meter
+    REGISTER_MAPPING(dt::SWITCH, TAG_TYPE_DEVICE_DATA, FL_(activated), 0, 1), // activated
+    REGISTER_MAPPING(dt::SWITCH, TAG_TYPE_DEVICE_DATA, FL_(flowTempHc), 1, 1), // flowtemphc
+    REGISTER_MAPPING(dt::SWITCH, TAG_TYPE_DEVICE_DATA, FL_(status), 2, 1), // status
+    REGISTER_MAPPING(dt::CONTROLLER, TAG_TYPE_DEVICE_DATA, FL_(dateTime), 0, 13), // datetime
+    REGISTER_MAPPING(dt::ALERT, TAG_TYPE_DEVICE_DATA, FL_(setFlowTemp), 0, 1), // setflowtemp
+    REGISTER_MAPPING(dt::ALERT, TAG_TYPE_DEVICE_DATA, FL_(setBurnPow), 1, 1), // setburnpow
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(flowTempVf), 0, 1), // flowtempvf
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(input), 1, 1), // input
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(outPower), 2, 1), // outpow
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(setPower), 3, 1), // setpower
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(setPoint), 4, 1), // setpoint
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(minV), 5, 1), // minv
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(maxV), 6, 1), // maxv
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(minT), 7, 1), // mint
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(maxT), 8, 1), // maxt
+    REGISTER_MAPPING(dt::EXTENSION, TAG_TYPE_DEVICE_DATA, FL_(mode), 9, 1), // mode
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(outFresh), 0, 1), // outfresh
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(inFresh), 1, 1), // infresh
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(outEx), 2, 1), // outexhaust
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(inEx), 3, 1), // inexhaust
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(ventInSpeed), 4, 1), // ventinspeed
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(ventOutSpeed), 5, 1), // ventoutspeed
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(ventMode), 6, 1), // ventmode
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(airquality), 7, 1), // airquality
+    REGISTER_MAPPING(dt::VENTILATION, TAG_TYPE_DEVICE_DATA, FL_(airHumidity), 8, 1), // airhumidity
+};
+
+} // namespace emsesp
diff --git a/src/modbus_test.h b/src/modbus_test.h
new file mode 100644
index 000000000..832f5d6b1
--- /dev/null
+++ b/src/modbus_test.h
@@ -0,0 +1,106 @@
+#if defined(EMSESP_STANDALONE) || defined(EMSESP_TEST)
+
+#ifndef MODBUS_TEST_H
+#define MODBUS_TEST_H
+
+#include <cstdint>
+#include <vector>
+
+// Mocked ModbusMessage for tests
+
+enum Error : uint8_t {
+    SUCCESS                = 0x00,
+    ILLEGAL_FUNCTION       = 0x01,
+    ILLEGAL_DATA_ADDRESS   = 0x02,
+    ILLEGAL_DATA_VALUE     = 0x03,
+    SERVER_DEVICE_FAILURE  = 0x04,
+    ACKNOWLEDGE            = 0x05,
+    SERVER_DEVICE_BUSY     = 0x06,
+    NEGATIVE_ACKNOWLEDGE   = 0x07,
+    MEMORY_PARITY_ERROR    = 0x08,
+    GATEWAY_PATH_UNAVAIL   = 0x0A,
+    GATEWAY_TARGET_NO_RESP = 0x0B,
+    TIMEOUT                = 0xE0,
+    INVALID_SERVER         = 0xE1,
+    CRC_ERROR              = 0xE2, // only for Modbus-RTU
+    FC_MISMATCH            = 0xE3,
+    SERVER_ID_MISMATCH     = 0xE4,
+    PACKET_LENGTH_ERROR    = 0xE5,
+    PARAMETER_COUNT_ERROR  = 0xE6,
+    PARAMETER_LIMIT_ERROR  = 0xE7,
+    REQUEST_QUEUE_FULL     = 0xE8,
+    ILLEGAL_IP_OR_PORT     = 0xE9,
+    IP_CONNECTION_FAILED   = 0xEA,
+    TCP_HEAD_MISMATCH      = 0xEB,
+    EMPTY_MESSAGE          = 0xEC,
+    ASCII_FRAME_ERR        = 0xED,
+    ASCII_CRC_ERR          = 0xEE,
+    ASCII_INVALID_CHAR     = 0xEF,
+    BROADCAST_ERROR        = 0xF0,
+    UNDEFINED_ERROR        = 0xFF // otherwise uncovered communication error
+};
+
+class ModbusMessage {
+  public:
+    ModbusMessage() {
+    }
+
+    ModbusMessage(std::vector<uint8_t> data) {
+        _data = data;
+    }
+
+    void get(uint16_t index, uint8_t & value) const {
+        value = _data[index];
+    }
+
+    void get(uint16_t index, uint16_t & value) const {
+        value = (_data[index] << 8) + _data[index + 1];
+    }
+
+    void get(uint16_t index, std::vector<uint8_t> & data, uint8_t byte_count) const {
+        for (auto i = 0; i < byte_count; i++)
+            data.push_back(_data[i + index]);
+    }
+
+    void add(uint8_t value) {
+        _data.push_back(value);
+    }
+
+    void add(uint16_t value) {
+        _data.push_back(value >> 8);
+        _data.push_back(value & 0xff);
+    }
+
+    uint8_t getServerID() const {
+        return _data[0];
+    }
+
+    uint8_t getFunctionCode() const {
+        return _data[1];
+    }
+
+    Error getError() const {
+        if (_data.size() > 2) {
+            if (_data[1] & 0x80) {
+                return static_cast<Error>(_data[2]);
+            }
+        }
+        return SUCCESS;
+    }
+
+    Error setError(uint8_t serverID, uint8_t functionCode, Error errorCode) {
+        _data.reserve(3);
+        _data.shrink_to_fit();
+        _data.clear();
+        add(serverID);
+        add(static_cast<uint8_t>((functionCode | 0x80) & 0xFF));
+        add(static_cast<uint8_t>(errorCode));
+        return SUCCESS;
+    }
+
+    std::vector<uint8_t> _data;
+};
+
+#endif
+
+#endif
diff --git a/src/system.cpp b/src/system.cpp
index ecce25f21..92f7fc9b4 100644
--- a/src/system.cpp
+++ b/src/system.cpp
@@ -396,6 +396,11 @@ void System::reload_settings() {
         board_profile_  = settings.board_profile;
         telnet_enabled_ = settings.telnet_enabled;
 
+        modbus_enabled_     = settings.modbus_enabled;
+        modbus_port_        = settings.modbus_port;
+        modbus_max_clients_ = settings.modbus_max_clients;
+        modbus_timeout_     = settings.modbus_timeout;
+
         rx_gpio_     = settings.rx_gpio;
         tx_gpio_     = settings.tx_gpio;
         dallas_gpio_ = settings.dallas_gpio;
diff --git a/src/system.h b/src/system.h
index 1154da2eb..7d250cdc4 100644
--- a/src/system.h
+++ b/src/system.h
@@ -120,6 +120,22 @@ class System {
         return telnet_enabled_;
     }
 
+    bool modbus_enabled() {
+        return modbus_enabled_;
+    }
+
+    uint16_t modbus_port() {
+        return modbus_port_;
+    }
+
+    uint8_t modbus_max_clients() {
+        return modbus_max_clients_;
+    }
+
+    uint32_t modbus_timeout() {
+        return modbus_timeout_;
+    }
+
     bool analog_enabled() {
         return analog_enabled_;
     }
@@ -339,6 +355,10 @@ class System {
     uint8_t     enum_format_;
     bool        readonly_mode_;
     String      version_;
+    bool        modbus_enabled_;
+    uint16_t    modbus_port_;
+    uint8_t     modbus_max_clients_;
+    uint32_t    modbus_timeout_;
 
     // ethernet
     uint8_t phy_type_;
diff --git a/src/test/test.cpp b/src/test/test.cpp
index 648b24e47..9ff67b305 100644
--- a/src/test/test.cpp
+++ b/src/test/test.cpp
@@ -1759,6 +1759,215 @@ void Test::run_test(uuid::console::Shell & shell, const std::string & cmd, const
         ok = true;
     }
 
+    if (command == "modbus") {
+        shell.printfln("Testing Modbus...");
+
+        System::test_set_all_active(true);
+        add_device(0x08, 172); // boiler: Enviline/Compress 6000AW/Hybrid 3000-7000iAW/SupraEco/Geo 5xx/WLW196i
+
+        const auto & it = std::find_if(EMSESP::emsdevices.begin(), EMSESP::emsdevices.end(), [&](const std::unique_ptr<EMSdevice> & dev) {
+            return dev && dev->device_id() == 0x08;
+        });
+
+        if (it == EMSESP::emsdevices.end()) {
+            EMSESP::logger().err("ERROR - can not find mocked heatpump device");
+            return;
+        }
+
+        const auto & device = *it;
+
+        {
+            auto test_int8 = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(1);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("INT8   %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    shell.printf("INT8   %s: %d ", shortname.c_str(), (int8_t)modbus_regs[0]);
+                    if ((int8_t)modbus_regs[0] == (int8_t)EMS_VALUE_DEFAULT_INT8_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (int8_t)EMS_VALUE_DEFAULT_INT8_DUMMY, (int8_t)modbus_regs[0]);
+                }
+            };
+
+            auto test_uint8 = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(1);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("UINT8  %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    shell.printf("UINT8  %s: %d ", shortname.c_str(), (uint8_t)modbus_regs[0]);
+                    if ((uint8_t)modbus_regs[0] == (uint8_t)EMS_VALUE_DEFAULT_UINT8_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (uint8_t)EMS_VALUE_DEFAULT_UINT8_DUMMY, (uint8_t)modbus_regs[0]);
+                }
+            };
+
+            auto test_int16 = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(1);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("INT16  %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    shell.printf("INT16  %s: %d ", shortname.c_str(), (int16_t)modbus_regs[0]);
+                    if ((int16_t)modbus_regs[0] == (int16_t)EMS_VALUE_DEFAULT_INT16_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (int16_t)EMS_VALUE_DEFAULT_INT16_DUMMY, (int16_t)modbus_regs[0]);
+                }
+            };
+
+            auto test_uint16 = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(1);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("UINT16 %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    shell.printf("UINT16 %s: %d ", shortname.c_str(), (uint16_t)modbus_regs[0]);
+                    if ((uint16_t)modbus_regs[0] == (uint16_t)EMS_VALUE_DEFAULT_UINT16_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (uint16_t)EMS_VALUE_DEFAULT_UINT16_DUMMY, (uint16_t)modbus_regs[0]);
+                }
+            };
+
+            auto test_uint24 = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(2);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("UINT24 %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    uint32_t value = ((uint32_t)modbus_regs[0] << 16) | (uint32_t)modbus_regs[1];
+                    shell.printf("UINT24 %s: %d ", shortname.c_str(), value);
+                    if (value == (uint32_t)EMS_VALUE_DEFAULT_UINT24_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (uint32_t)EMS_VALUE_DEFAULT_UINT24_DUMMY, value);
+                }
+            };
+
+            /* there seem to be no uint32 entities to run this test on.
+            auto test_uint32 = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(2);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("UINT32  %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    uint32_t value = ((uint32_t)modbus_regs[0] << 16) | (uint32_t)modbus_regs[1];
+                    shell.printf("UINT32  %s: %d ", shortname.c_str(), value);
+                    if (value == (uint32_t)EMS_VALUE_DEFAULT_UINT32_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (uint32_t)EMS_VALUE_DEFAULT_UINT32_DUMMY, value);
+                }
+            };
+            */
+
+            auto test_bool = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(1);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("BOOL   %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    shell.printf("BOOL   %s: %d ", shortname.c_str(), (uint8_t)modbus_regs[0]);
+                    if ((uint8_t)modbus_regs[0] == (uint8_t)EMS_VALUE_DEFAULT_BOOL_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (uint8_t)EMS_VALUE_DEFAULT_BOOL_DUMMY, (uint8_t)modbus_regs[0]);
+                }
+            };
+
+            auto test_enum = [&](const std::unique_ptr<EMSdevice> & device, uint8_t tag, const std::string & shortname) {
+                std::vector<uint16_t> modbus_regs(1);
+                if (auto result = device->get_modbus_value(tag, shortname, modbus_regs)) {
+                    shell.printf("ENUM   %s FAILED (ERROR %d)\n", shortname.c_str(), result);
+                } else {
+                    shell.printf("ENUM   %s: %d ", shortname.c_str(), (uint8_t)modbus_regs[0]);
+                    if ((uint8_t)modbus_regs[0] == (uint8_t)EMS_VALUE_DEFAULT_ENUM_DUMMY)
+                        shell.printfln("[OK]");
+                    else
+                        shell.printfln("[ERROR] - expected %d, got %d", (uint8_t)EMS_VALUE_DEFAULT_ENUM_DUMMY, (uint8_t)modbus_regs[0]);
+                }
+            };
+
+            shell.println();
+            shell.printfln("Testing device->get_modbus_value():");
+            test_int8(device, DeviceValueTAG::TAG_DEVICE_DATA, "mintempsilent");
+            test_uint8(device, DeviceValueTAG::TAG_DEVICE_DATA, "selflowtemp");
+            test_int16(device, DeviceValueTAG::TAG_DEVICE_DATA, "outdoortemp");
+            test_uint16(device, DeviceValueTAG::TAG_DEVICE_DATA, "rettemp");
+            // test_uint32(device, DeviceValueTAG::TAG_DEVICE_DATA, "heatstarts"); // apparently there are no uint32 entities?
+            test_uint24(device, DeviceValueTAG::TAG_DEVICE_DATA, "heatstarts");
+            test_bool(device, DeviceValueTAG::TAG_DEVICE_DATA, "heatingactivated");
+            test_enum(device, DeviceValueTAG::TAG_DEVICE_DATA, "pumpmode");
+        }
+
+        // modbus_value_to_json
+        {
+            shell.println();
+            shell.printfln("Testing device->modbus_value_to_json():");
+
+            std::vector<uint8_t> modbus_bytes(2);
+            JsonDocument         input;
+            JsonObject           inputObject = input.to<JsonObject>();
+            modbus_bytes[0]                  = 0;
+            modbus_bytes[1]                  = EMS_VALUE_DEFAULT_UINT8_DUMMY;
+            device->modbus_value_to_json(DeviceValueTAG::TAG_DEVICE_DATA, "selflowtemp", modbus_bytes, inputObject);
+
+            std::string jsonString;
+            serializeJson(inputObject, jsonString);
+            shell.printf("UINT8   %s: %s (%d) ", "selflowtemp", jsonString.c_str(), inputObject["value"].as<int>());
+
+            if (inputObject["value"] == (uint8_t)EMS_VALUE_DEFAULT_UINT8_DUMMY)
+                shell.println("[OK]");
+            else
+                shell.println("[ERROR]");
+        }
+
+        // handleRead
+        {
+            shell.println();
+            shell.printfln("Testing modbus->handleRead():");
+
+            uint16_t reg = Modbus::REGISTER_BLOCK_SIZE * DeviceValueTAG::TAG_DEVICE_DATA + 209; // mintempsilent is tag 2 (TAG_DEVICE_DATA), offset 209
+
+            ModbusMessage request({device->device_type(), 0x03, static_cast<unsigned char>(reg >> 8), static_cast<unsigned char>(reg & 0xff), 0, 1});
+            auto          response = EMSESP::modbus_->handleRead(request);
+
+            if (response.getError() == SUCCESS) {
+                shell.print("mintempsilent MODBUS response:");
+                for (const auto & d : response._data) {
+                    shell.printf(" %d", d);
+                }
+                if (response._data.size() == 5 && response._data[3] == 0 && response._data[4] == (uint8_t)EMS_VALUE_DEFAULT_INT8_DUMMY) {
+                    shell.printf(" [OK]");
+                } else {
+                    shell.printf(" [ERROR - invalid response]");
+                }
+                shell.println();
+            } else {
+                shell.printf("mintempsilent [MODBUS ERROR %d]\n", response.getError());
+            }
+        }
+
+        // handleWrite
+        {
+            shell.println();
+            shell.printfln("Testing modbus->handleWrite():");
+
+            uint16_t      reg = Modbus::REGISTER_BLOCK_SIZE * DeviceValueTAG::TAG_DEVICE_DATA + 4; // selflowtemp is tag 2 (TAG_DEVICE_DATA), offset 4
+            ModbusMessage request({device->device_type(), 0x06, static_cast<unsigned char>(reg >> 8), static_cast<unsigned char>(reg & 0xff), 0, 1, 2, 0, 45});
+            auto          response = EMSESP::modbus_->handleWrite(request);
+
+            if (response.getError() == SUCCESS) {
+                shell.print("selflowtemp MODBUS response:");
+                for (const auto & d : response._data) {
+                    shell.printf(" %d", d);
+                }
+                shell.println(" [OK]");
+            } else {
+                shell.printf("selflowtemp [MODBUS ERROR %d]\n", response.getError());
+            }
+        }
+
+        ok = true;
+    }
+
     if (command == "poll2") {
         shell.printfln("Testing Tx Sending last message on queue...");
 
diff --git a/src/web/WebSettingsService.cpp b/src/web/WebSettingsService.cpp
index e95885777..054947c61 100644
--- a/src/web/WebSettingsService.cpp
+++ b/src/web/WebSettingsService.cpp
@@ -77,6 +77,10 @@ void WebSettings::read(WebSettings & settings, JsonObject root) {
     root["eth_clock_mode"]        = settings.eth_clock_mode;
     String platform               = EMSESP_PLATFORM;
     root["platform"]              = (platform == "ESP32" && EMSESP::system_.PSram()) ? "ESP32R" : platform;
+    root["modbus_enabled"]        = settings.modbus_enabled;
+    root["modbus_port"]           = settings.modbus_port;
+    root["modbus_max_clients"]    = settings.modbus_max_clients;
+    root["modbus_timeout"]        = settings.modbus_timeout;
 }
 
 // call on initialization and also when settings are updated via web or console
@@ -272,6 +276,22 @@ StateUpdateResult WebSettings::update(JsonObject root, WebSettings & settings) {
     settings.low_clock = root["low_clock"];
     check_flag(prev, settings.low_clock, ChangeFlags::RESTART);
 
+    prev                    = settings.modbus_enabled;
+    settings.modbus_enabled = root["modbus_enabled"] | EMSESP_DEFAULT_MODBUS_ENABLED;
+    check_flag(prev, settings.modbus_enabled, ChangeFlags::RESTART);
+
+    prev                 = settings.modbus_port;
+    settings.modbus_port = root["modbus_port"] | EMSESP_DEFAULT_MODBUS_PORT;
+    check_flag(prev, settings.modbus_port, ChangeFlags::RESTART);
+
+    prev                        = settings.modbus_max_clients;
+    settings.modbus_max_clients = root["modbus_max_clients"] | EMSESP_DEFAULT_MODBUS_MAX_CLIENTS;
+    check_flag(prev, settings.modbus_max_clients, ChangeFlags::RESTART);
+
+    prev                    = settings.modbus_timeout;
+    settings.modbus_timeout = root["modbus_timeout"] | EMSESP_DEFAULT_MODBUS_TIMEOUT;
+    check_flag(prev, settings.modbus_timeout, ChangeFlags::RESTART);
+
     //
     // these may need mqtt restart to rebuild HA discovery topics
     //
diff --git a/src/web/WebSettingsService.h b/src/web/WebSettingsService.h
index c645127ff..56830e8a7 100644
--- a/src/web/WebSettingsService.h
+++ b/src/web/WebSettingsService.h
@@ -68,6 +68,10 @@ class WebSettings {
     uint8_t  weblog_buffer;
     bool     weblog_compact;
     bool     fahrenheit;
+    bool     modbus_enabled;
+    uint16_t modbus_port;
+    uint8_t  modbus_max_clients;
+    uint32_t modbus_timeout;
 
     uint8_t phy_type;
     int8_t  eth_power; // -1 means disabled