From 8b0d91a9b816f963793c126fbff32b321451bf31 Mon Sep 17 00:00:00 2001
From: proddy <paul@derbyshire.nl>
Date: Sun, 24 Mar 2019 19:45:59 +0100
Subject: [PATCH] ignore null telegrams

---
 src/ems.cpp     | 25 +++++++++++++------------
 src/emsuart.cpp |  9 ++-------
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/src/ems.cpp b/src/ems.cpp
index 1e857dc8f..2e640915c 100644
--- a/src/ems.cpp
+++ b/src/ems.cpp
@@ -579,33 +579,34 @@ void _createValidate() {
 
 
 /*
- * Entry point TODO: tidy up
+ * Entry point triggered by an interrupt in emsuart.cpp
+ * length is only data bytes, excluding the BRK
+ * Read commands are asynchronous as they're handled by the interrupt
+ * When a telegram is processed we forcefully erase it from the stack to prevent overflow
  */
 void ems_parseTelegram(uint8_t * telegram, uint8_t length) {
-    _ems_readTelegram(telegram, length);
-    // now clear it just be safe
-    for (uint8_t i = 0; i < EMS_MAXBUFFERSIZE; i++) {
-        telegram[i] = 0x00;
+    if ((length != 0) && (telegram[0] != 0x00)) {
+        _ems_readTelegram(telegram, length);
     }
+    // now clear the Rx buffer just be safe and prevent duplicates
+    for (uint8_t i = 0; i < EMS_MAXBUFFERSIZE; telegram[i++] = 0x00)
+        ; 
 }
 
 /**
- * the main logic that parses the telegram message, triggered by an interrupt in emsuart.cpp
- * length is only data bytes, excluding the BRK
- * Read commands are asynchronous as they're handled by the interrupt
+ * the main logic that parses the telegram message
  * When we receive a Poll Request we need to send any Tx packages quickly within a 200ms window
  */
 void _ems_readTelegram(uint8_t * telegram, uint8_t length) {
-    // check if we just received a single byte
-    // it could well be a Poll request from the boiler for us, which will have a value of 0x8B (0x0B | 0x80)
-    // or either a return code like 0x01 or 0x04 from the last Write command
-
     // create the Rx package
     static _EMS_RxTelegram EMS_RxTelegram;
     EMS_RxTelegram.length    = length;
     EMS_RxTelegram.telegram  = telegram;
     EMS_RxTelegram.timestamp = millis();
 
+    // check if we just received a single byte
+    // it could well be a Poll request from the boiler for us, which will have a value of 0x8B (0x0B | 0x80)
+    // or either a return code like 0x01 or 0x04 from the last Write command
     if (length == 1) {
         uint8_t value = telegram[0]; // 1st byte of data package
 
diff --git a/src/emsuart.cpp b/src/emsuart.cpp
index 788d9bd46..65b479b0b 100644
--- a/src/emsuart.cpp
+++ b/src/emsuart.cpp
@@ -71,14 +71,9 @@ static void emsuart_rx_intr_handler(void * para) {
  * The full buffer is sent to the ems_parseTelegram() function in ems.cpp.
  */
 static void ICACHE_FLASH_ATTR emsuart_recvTask(os_event_t * events) {
-    // get next free EMS Receive buffer
     _EMSRxBuf * pCurrent = pEMSRxBuf;
-    pEMSRxBuf            = paEMSRxBuf[++emsRxBufIdx % EMS_MAXBUFFERS];
-
-    // transmit EMS buffer, excluding the BRK
-    if (pCurrent->writePtr > 1) {
-        ems_parseTelegram((uint8_t *)pCurrent->buffer, (pCurrent->writePtr) - 1);
-    }
+    ems_parseTelegram((uint8_t *)pCurrent->buffer, (pCurrent->writePtr) - 1); //  transmit EMS buffer, excluding the BRK
+    pEMSRxBuf = paEMSRxBuf[++emsRxBufIdx % EMS_MAXBUFFERS];                   // next free EMS Receive buffer
 }
 
 /*