small change

src/emsesp.cpp

@@ -569,6 +569,7 @@ void EMSESP::incoming_telegram(uint8_t * data, const uint8_t length) {
     // check first for echo
     uint8_t first_value = data[0];
     if (((first_value & 0x7F) == txservice_.ems_bus_id()) && (length > 1)) {
+        DEBUG_LOG(F("Tx echo"));
         return; // it's an echo
     }
 

src/mixing.cpp

@@ -153,7 +153,7 @@ void Mixing::process_MMStatusMessage(std::shared_ptr<const Telegram> telegram) {
     // the heating circuit is determine by which device_id it is, 0x20 - 0x23
     // 0x21 is position 2. 0x20 is typically reserved for the WM10 switch module
     // see https://github.com/proddy/EMS-ESP/issues/270 and https://github.com/proddy/EMS-ESP/issues/386#issuecomment-629610918
-    hc_ = 0x22 - device_id();
+    hc_ = device_id() - 0x20 + 1;
     telegram->read_value(flowTemp_, 1); // is * 10
     telegram->read_value(pumpMod_, 3);
     telegram->read_value(flowSetTemp_, 0);

src/telegram.cpp

@@ -268,7 +268,7 @@ void RxService::add(uint8_t * data, uint8_t length) {
     uint8_t   message_length;
 
     // work out depending on the type where the data message block starts
-    if (data[2] < 0xF0) {
+    if (data[2] < 0xF0 || length < 6) {
         // EMS 1.0
         type_id        = data[2];
         message_data   = data + 4;   // message block starts at 5th byte