diff --git a/tasmota/OpenTherm.cpp b/tasmota/OpenTherm.cpp
new file mode 100644
index 000000000..a08608649
--- /dev/null
+++ b/tasmota/OpenTherm.cpp
@@ -0,0 +1,410 @@
+/*
+OpenTherm.cpp - OpenTherm Communication Library For Arduino, ESP8266
+Copyright 2018, Ihor Melnyk
+*/
+
+#include "OpenTherm.h"
+
+OpenTherm::OpenTherm(int inPin, int outPin, bool isSlave):
+	status(OpenThermStatus::NOT_INITIALIZED),
+	inPin(inPin),
+	outPin(outPin),
+	isSlave(isSlave),
+	response(0),
+	responseStatus(OpenThermResponseStatus::NONE),
+	responseTimestamp(0),
+	handleInterruptCallback(NULL),
+	processResponseCallback(NULL)
+{
+}
+
+void OpenTherm::begin(void(*handleInterruptCallback)(void), void(*processResponseCallback)(unsigned long, int))
+{
+	pinMode(inPin, INPUT);
+	pinMode(outPin, OUTPUT);
+	if (handleInterruptCallback != NULL) {
+		this->handleInterruptCallback = handleInterruptCallback;
+		attachInterrupt(digitalPinToInterrupt(inPin), handleInterruptCallback, CHANGE);
+	}
+	activateBoiler();
+	status = OpenThermStatus::READY;
+	this->processResponseCallback = processResponseCallback;
+}
+
+void OpenTherm::begin(void(*handleInterruptCallback)(void))
+{
+	begin(handleInterruptCallback, NULL);
+}
+
+bool ICACHE_RAM_ATTR OpenTherm::isReady()
+{
+	return status == OpenThermStatus::READY;
+}
+
+int ICACHE_RAM_ATTR OpenTherm::readState() {
+	return digitalRead(inPin);
+}
+
+void OpenTherm::setActiveState() {
+	digitalWrite(outPin, LOW);
+}
+
+void OpenTherm::setIdleState() {
+	digitalWrite(outPin, HIGH);
+}
+
+void OpenTherm::activateBoiler() {
+	setIdleState();
+	delay(1000);
+}
+
+void OpenTherm::sendBit(bool high) {
+	if (high) setActiveState(); else setIdleState();
+	delayMicroseconds(500);
+	if (high) setIdleState(); else setActiveState();
+	delayMicroseconds(500);
+}
+
+bool OpenTherm::sendRequestAync(unsigned long request)
+{
+	//Serial.println("Request: " + String(request, HEX));
+	noInterrupts();
+	const bool ready = isReady();
+	interrupts();
+
+	if (!ready)
+	  return false;
+
+	status = OpenThermStatus::REQUEST_SENDING;
+	response = 0;
+	responseStatus = OpenThermResponseStatus::NONE;
+
+	sendBit(HIGH); //start bit
+	for (int i = 31; i >= 0; i--) {
+		sendBit(bitRead(request, i));
+	}
+	sendBit(HIGH); //stop bit
+	setIdleState();
+
+	status = OpenThermStatus::RESPONSE_WAITING;
+	responseTimestamp = micros();
+	return true;
+}
+
+unsigned long OpenTherm::sendRequest(unsigned long request)
+{
+	if (!sendRequestAync(request)) return 0;
+	while (!isReady()) {
+		process();
+		yield();
+	}
+	return response;
+}
+
+bool OpenTherm::sendResponse(unsigned long request)
+{
+	status = OpenThermStatus::REQUEST_SENDING;
+	response = 0;
+	responseStatus = OpenThermResponseStatus::NONE;
+
+	sendBit(HIGH); //start bit
+	for (int i = 31; i >= 0; i--) {
+		sendBit(bitRead(request, i));
+	}
+	sendBit(HIGH); //stop bit
+	setIdleState();
+	status = OpenThermStatus::READY;
+	return true;
+}
+
+OpenThermResponseStatus OpenTherm::getLastResponseStatus()
+{
+	return responseStatus;
+}
+
+void ICACHE_RAM_ATTR OpenTherm::handleInterrupt()
+{
+	if (isReady())
+	{
+		if (isSlave && readState() == HIGH) {
+		   status = OpenThermStatus::RESPONSE_WAITING;
+		}
+		else {
+			return;
+		}
+	}
+
+	unsigned long newTs = micros();
+	if (status == OpenThermStatus::RESPONSE_WAITING) {
+		if (readState() == HIGH) {
+			status = OpenThermStatus::RESPONSE_START_BIT;
+			responseTimestamp = newTs;
+		}
+		else {
+			status = OpenThermStatus::RESPONSE_INVALID;
+			responseTimestamp = newTs;
+		}
+	}
+	else if (status == OpenThermStatus::RESPONSE_START_BIT) {
+		if ((newTs - responseTimestamp < 750) && readState() == LOW) {
+			status = OpenThermStatus::RESPONSE_RECEIVING;
+			responseTimestamp = newTs;
+			responseBitIndex = 0;
+		}
+		else {
+			status = OpenThermStatus::RESPONSE_INVALID;
+			responseTimestamp = newTs;
+		}
+	}
+	else if (status == OpenThermStatus::RESPONSE_RECEIVING) {
+		if ((newTs - responseTimestamp) > 750) {
+			if (responseBitIndex < 32) {
+				response = (response << 1) | !readState();
+				responseTimestamp = newTs;
+				responseBitIndex++;
+			}
+			else { //stop bit
+				status = OpenThermStatus::RESPONSE_READY;
+				responseTimestamp = newTs;
+			}
+		}
+	}
+}
+
+void OpenTherm::process()
+{
+	noInterrupts();
+	OpenThermStatus st = status;
+	unsigned long ts = responseTimestamp;
+	interrupts();
+
+	if (st == OpenThermStatus::READY) return;
+	unsigned long newTs = micros();
+	if (st != OpenThermStatus::NOT_INITIALIZED && (newTs - ts) > 1000000) {
+		status = OpenThermStatus::READY;
+		responseStatus = OpenThermResponseStatus::TIMEOUT;
+		if (processResponseCallback != NULL) {
+			processResponseCallback(response, responseStatus);
+		}
+	}
+	else if (st == OpenThermStatus::RESPONSE_INVALID) {
+		status = OpenThermStatus::DELAY;
+		responseStatus = OpenThermResponseStatus::INVALID;
+		if (processResponseCallback != NULL) {
+			processResponseCallback(response, responseStatus);
+		}
+	}
+	else if (st == OpenThermStatus::RESPONSE_READY) {
+		status = OpenThermStatus::DELAY;
+		responseStatus = (isSlave ? isValidRequest(response) : isValidResponse(response)) ? OpenThermResponseStatus::SUCCESS : OpenThermResponseStatus::INVALID;
+		if (processResponseCallback != NULL) {
+			processResponseCallback(response, responseStatus);
+		}
+	}
+	else if (st == OpenThermStatus::DELAY) {
+		if ((newTs - ts) > 100000) {
+			status = OpenThermStatus::READY;
+		}
+	}
+}
+
+bool OpenTherm::parity(unsigned long frame) //odd parity
+{
+	byte p = 0;
+	while (frame > 0)
+	{
+		if (frame & 1) p++;
+		frame = frame >> 1;
+	}
+	return (p & 1);
+}
+
+OpenThermMessageType OpenTherm::getMessageType(unsigned long message)
+{
+	OpenThermMessageType msg_type = static_cast<OpenThermMessageType>((message >> 28) & 7);
+	return msg_type;
+}
+
+OpenThermMessageID OpenTherm::getDataID(unsigned long frame)
+{
+	return (OpenThermMessageID)((frame >> 16) & 0xFF);
+}
+
+unsigned long OpenTherm::buildRequest(OpenThermMessageType type, OpenThermMessageID id, unsigned int data)
+{
+	unsigned long request = data;
+	if (type == OpenThermMessageType::WRITE_DATA) {
+		request |= 1ul << 28;
+	}
+	request |= ((unsigned long)id) << 16;
+	if (OpenTherm::parity(request)) request |= (1ul << 31);
+	return request;
+}
+
+unsigned long OpenTherm::buildResponse(OpenThermMessageType type, OpenThermMessageID id, unsigned int data)
+{
+	unsigned long response = data;
+	response |= type << 28;
+	response |= ((unsigned long)id) << 16;
+	if (OpenTherm::parity(response)) response |= (1ul << 31);
+	return response;
+}
+
+bool OpenTherm::isValidResponse(unsigned long response)
+{
+	if (OpenTherm::parity(response)) return false;
+	byte msgType = (response << 1) >> 29;
+	return msgType == READ_ACK || msgType == WRITE_ACK;
+}
+
+bool OpenTherm::isValidRequest(unsigned long request)
+{
+	if (OpenTherm::parity(request)) return false;
+	byte msgType = (request << 1) >> 29;
+	return msgType == READ_DATA || msgType == WRITE_DATA;
+}
+
+void OpenTherm::end() {
+	if (this->handleInterruptCallback != NULL) {
+		detachInterrupt(digitalPinToInterrupt(inPin));
+	}
+}
+
+const char *OpenTherm::statusToString(OpenThermResponseStatus status)
+{
+	switch (status) {
+		case NONE:	return "NONE";
+		case SUCCESS: return "SUCCESS";
+		case INVALID: return "INVALID";
+		case TIMEOUT: return "TIMEOUT";
+		default:	  return "UNKNOWN";
+	}
+}
+
+const char *OpenTherm::messageTypeToString(OpenThermMessageType message_type)
+{
+	switch (message_type) {
+		case READ_DATA:	   return "READ_DATA";
+		case WRITE_DATA:	  return "WRITE_DATA";
+		case INVALID_DATA:	return "INVALID_DATA";
+		case RESERVED:		return "RESERVED";
+		case READ_ACK:		return "READ_ACK";
+		case WRITE_ACK:	   return "WRITE_ACK";
+		case DATA_INVALID:	return "DATA_INVALID";
+		case UNKNOWN_DATA_ID: return "UNKNOWN_DATA_ID";
+		default:			  return "UNKNOWN";
+	}
+}
+
+//building requests
+
+unsigned long OpenTherm::buildSetBoilerStatusRequest(bool enableCentralHeating, bool enableHotWater, bool enableCooling, bool enableOutsideTemperatureCompensation, bool enableCentralHeating2) {
+	unsigned int data = enableCentralHeating | (enableHotWater << 1) | (enableCooling << 2) | (enableOutsideTemperatureCompensation << 3) | (enableCentralHeating2 << 4);
+	data <<= 8;
+	return buildRequest(OpenThermMessageType::READ_DATA, OpenThermMessageID::Status, data);
+}
+
+unsigned long OpenTherm::buildSetBoilerTemperatureRequest(float temperature) {
+	unsigned int data = temperatureToData(temperature);
+	return buildRequest(OpenThermMessageType::WRITE_DATA, OpenThermMessageID::TSet, data);
+}
+
+unsigned long OpenTherm::buildSetHotWaterTemperatureRequest(float temperature) {
+	unsigned int data = temperatureToData(temperature);
+	return buildRequest(OpenThermMessageType::WRITE_DATA, OpenThermMessageID::TdhwSet, data);
+}
+
+unsigned long OpenTherm::buildGetBoilerTemperatureRequest() {
+	return buildRequest(OpenThermMessageType::READ_DATA, OpenThermMessageID::Tboiler, 0);
+}
+
+unsigned long OpenTherm::buildSlaveConfigurationRequest() {
+	return buildRequest(OpenThermMessageType::READ_DATA, OpenThermMessageID::SConfigSMemberIDcode, 0);
+}
+
+//parsing responses
+bool OpenTherm::isFault(unsigned long response) {
+	return response & 0x1;
+}
+
+bool OpenTherm::isCentralHeatingActive(unsigned long response) {
+	return response & 0x2;
+}
+
+bool OpenTherm::isHotWaterActive(unsigned long response) {
+	return response & 0x4;
+}
+
+bool OpenTherm::isFlameOn(unsigned long response) {
+	return response & 0x8;
+}
+
+bool OpenTherm::isCoolingActive(unsigned long response) {
+	return response & 0x10;
+}
+
+bool OpenTherm::isDiagnostic(unsigned long response) {
+	return response & 0x40;
+}
+
+uint16_t OpenTherm::getUInt(const unsigned long response) {
+	const uint16_t u88 = response & 0xffff;
+	return u88;
+}
+
+float OpenTherm::getFloat(const unsigned long response) {
+	const uint16_t u88 = getUInt(response);
+	const float f = (u88 & 0x8000) ? -(0x10000L - u88) / 256.0f : u88 / 256.0f;
+	return f;
+}
+
+unsigned int OpenTherm::temperatureToData(float temperature) {
+	if (temperature < 0) temperature = 0;
+	if (temperature > 100) temperature = 100;
+	unsigned int data = (unsigned int)(temperature * 256);
+	return data;
+}
+
+//basic requests
+
+unsigned long OpenTherm::setBoilerStatus(bool enableCentralHeating, bool enableHotWater, bool enableCooling, bool enableOutsideTemperatureCompensation, bool enableCentralHeating2) {
+	return sendRequest(buildSetBoilerStatusRequest(enableCentralHeating, enableHotWater, enableCooling, enableOutsideTemperatureCompensation, enableCentralHeating2));
+}
+
+bool OpenTherm::setBoilerTemperature(float temperature) {
+	unsigned long response = sendRequest(buildSetBoilerTemperatureRequest(temperature));
+	return isValidResponse(response);
+}
+
+bool OpenTherm::setHotWaterTemperature(float temperature) {
+	unsigned long response = sendRequest(buildSetHotWaterTemperatureRequest(temperature));
+	return isValidResponse(response);
+}
+
+float OpenTherm::getBoilerTemperature() {
+	unsigned long response = sendRequest(buildGetBoilerTemperatureRequest());
+	return isValidResponse(response) ? getFloat(response) : 0;
+}
+
+float OpenTherm::getReturnTemperature() {
+    unsigned long response = sendRequest(buildRequest(OpenThermRequestType::READ, OpenThermMessageID::Tret, 0));
+    return isValidResponse(response) ? getFloat(response) : 0;
+}
+
+float OpenTherm::getModulation() {
+    unsigned long response = sendRequest(buildRequest(OpenThermRequestType::READ, OpenThermMessageID::RelModLevel, 0));
+    return isValidResponse(response) ? getFloat(response) : 0;
+}
+
+float OpenTherm::getPressure() {
+    unsigned long response = sendRequest(buildRequest(OpenThermRequestType::READ, OpenThermMessageID::CHPressure, 0));
+    return isValidResponse(response) ? getFloat(response) : 0;
+}
+
+unsigned char OpenTherm::getFault() {
+    return ((sendRequest(buildRequest(OpenThermRequestType::READ, OpenThermMessageID::ASFflags, 0)) >> 8) & 0xff);
+}
+
+unsigned long OpenTherm::getSlaveConfiguration() {
+	return sendRequest(buildSlaveConfigurationRequest());
+}
\ No newline at end of file
diff --git a/tasmota/OpenTherm.h b/tasmota/OpenTherm.h
new file mode 100644
index 000000000..22bf965ad
--- /dev/null
+++ b/tasmota/OpenTherm.h
@@ -0,0 +1,193 @@
+/*
+OpenTherm.h - OpenTherm Library for the ESP8266/Arduino platform
+https://github.com/ihormelnyk/OpenTherm
+http://ihormelnyk.com/pages/OpenTherm
+Licensed under MIT license
+Copyright 2018, Ihor Melnyk
+
+Frame Structure:
+P MGS-TYPE SPARE DATA-ID  DATA-VALUE
+0 000      0000  00000000 00000000 00000000
+*/
+
+#ifndef OpenTherm_h
+#define OpenTherm_h
+
+#include <stdint.h>
+#include <Arduino.h>
+
+enum OpenThermResponseStatus {
+	NONE,
+	SUCCESS,
+	INVALID,
+	TIMEOUT
+};
+
+
+enum OpenThermMessageType {
+	/*  Master to Slave */
+	READ_DATA       = B000,
+	READ            = READ_DATA, // for backwared compatibility
+	WRITE_DATA      = B001,
+	WRITE           = WRITE_DATA, // for backwared compatibility
+	INVALID_DATA    = B010,
+	RESERVED        = B011,
+	/* Slave to Master */
+	READ_ACK        = B100,
+	WRITE_ACK       = B101,
+	DATA_INVALID    = B110,
+	UNKNOWN_DATA_ID = B111
+};
+
+typedef OpenThermMessageType OpenThermRequestType; // for backwared compatibility
+
+enum OpenThermMessageID {
+	Status, // flag8 / flag8  Master and Slave Status flags.
+	TSet, // f8.8  Control setpoint  ie CH  water temperature setpoint (°C)
+	MConfigMMemberIDcode, // flag8 / u8  Master Configuration Flags /  Master MemberID Code
+	SConfigSMemberIDcode, // flag8 / u8  Slave Configuration Flags /  Slave MemberID Code
+	Command, // u8 / u8  Remote Command
+	ASFflags, // / OEM-fault-code  flag8 / u8  Application-specific fault flags and OEM fault code
+	RBPflags, // flag8 / flag8  Remote boiler parameter transfer-enable & read/write flags
+	CoolingControl, // f8.8  Cooling control signal (%)
+	TsetCH2, // f8.8  Control setpoint for 2e CH circuit (°C)
+	TrOverride, // f8.8  Remote override room setpoint
+	TSP, // u8 / u8  Number of Transparent-Slave-Parameters supported by slave
+	TSPindexTSPvalue, // u8 / u8  Index number / Value of referred-to transparent slave parameter.
+	FHBsize, // u8 / u8  Size of Fault-History-Buffer supported by slave
+	FHBindexFHBvalue, // u8 / u8  Index number / Value of referred-to fault-history buffer entry.
+	MaxRelModLevelSetting, // f8.8  Maximum relative modulation level setting (%)
+	MaxCapacityMinModLevel, // u8 / u8  Maximum boiler capacity (kW) / Minimum boiler modulation level(%)
+	TrSet, // f8.8  Room Setpoint (°C)
+	RelModLevel, // f8.8  Relative Modulation Level (%)
+	CHPressure, // f8.8  Water pressure in CH circuit  (bar)
+	DHWFlowRate, // f8.8  Water flow rate in DHW circuit. (litres/minute)
+	DayTime, // special / u8  Day of Week and Time of Day
+	Date, // u8 / u8  Calendar date
+	Year, // u16  Calendar year
+	TrSetCH2, // f8.8  Room Setpoint for 2nd CH circuit (°C)
+	Tr, // f8.8  Room temperature (°C)
+	Tboiler, // f8.8  Boiler flow water temperature (°C)
+	Tdhw, // f8.8  DHW temperature (°C)
+	Toutside, // f8.8  Outside temperature (°C)
+	Tret, // f8.8  Return water temperature (°C)
+	Tstorage, // f8.8  Solar storage temperature (°C)
+	Tcollector, // f8.8  Solar collector temperature (°C)
+	TflowCH2, // f8.8  Flow water temperature CH2 circuit (°C)
+	Tdhw2, // f8.8  Domestic hot water temperature 2 (°C)
+	Texhaust, // s16  Boiler exhaust temperature (°C)
+	TdhwSetUBTdhwSetLB = 48, // s8 / s8  DHW setpoint upper & lower bounds for adjustment  (°C)
+	MaxTSetUBMaxTSetLB, // s8 / s8  Max CH water setpoint upper & lower bounds for adjustment  (°C)
+	HcratioUBHcratioLB, // s8 / s8  OTC heat curve ratio upper & lower bounds for adjustment
+	TdhwSet = 56, // f8.8  DHW setpoint (°C)    (Remote parameter 1)
+	MaxTSet, // f8.8  Max CH water setpoint (°C)  (Remote parameters 2)
+	Hcratio, // f8.8  OTC heat curve ratio (°C)  (Remote parameter 3)
+	RemoteOverrideFunction = 100, // flag8 / -  Function of manual and program changes in master and remote room setpoint.
+	OEMDiagnosticCode = 115, // u16  OEM-specific diagnostic/service code
+	BurnerStarts, // u16  Number of starts burner
+	CHPumpStarts, // u16  Number of starts CH pump
+	DHWPumpValveStarts, // u16  Number of starts DHW pump/valve
+	DHWBurnerStarts, // u16  Number of starts burner during DHW mode
+	BurnerOperationHours, // u16  Number of hours that burner is in operation (i.e. flame on)
+	CHPumpOperationHours, // u16  Number of hours that CH pump has been running
+	DHWPumpValveOperationHours, // u16  Number of hours that DHW pump has been running or DHW valve has been opened
+	DHWBurnerOperationHours, // u16  Number of hours that burner is in operation during DHW mode
+	OpenThermVersionMaster, // f8.8  The implemented version of the OpenTherm Protocol Specification in the master.
+	OpenThermVersionSlave, // f8.8  The implemented version of the OpenTherm Protocol Specification in the slave.
+	MasterVersion, // u8 / u8  Master product version number and type
+	SlaveVersion, // u8 / u8  Slave product version number and type
+};
+
+enum OpenThermStatus {
+	NOT_INITIALIZED,
+	READY,
+	DELAY,
+	REQUEST_SENDING,
+	RESPONSE_WAITING,
+	RESPONSE_START_BIT,
+	RESPONSE_RECEIVING,
+	RESPONSE_READY,
+	RESPONSE_INVALID
+};
+
+class OpenTherm
+{
+public:
+	OpenTherm(int inPin = 4, int outPin = 5, bool isSlave = false);
+	volatile OpenThermStatus status;
+	void begin(void(*handleInterruptCallback)(void));
+	void begin(void(*handleInterruptCallback)(void), void(*processResponseCallback)(unsigned long, int));
+	bool isReady();
+	unsigned long sendRequest(unsigned long request);
+	bool sendResponse(unsigned long request);
+	bool sendRequestAync(unsigned long request);
+	static unsigned long buildRequest(OpenThermMessageType type, OpenThermMessageID id, unsigned int data);
+	static unsigned long buildResponse(OpenThermMessageType type, OpenThermMessageID id, unsigned int data);
+	OpenThermResponseStatus getLastResponseStatus();
+	const char *statusToString(OpenThermResponseStatus status);
+	void handleInterrupt();
+	void process();
+	void end();
+
+	static bool parity(unsigned long frame);
+	OpenThermMessageType getMessageType(unsigned long message);
+	OpenThermMessageID getDataID(unsigned long frame);
+	const char *messageTypeToString(OpenThermMessageType message_type);
+	bool isValidRequest(unsigned long request);
+	bool isValidResponse(unsigned long response);
+
+	//requests
+	unsigned long buildSetBoilerStatusRequest(bool enableCentralHeating, bool enableHotWater = false, bool enableCooling = false, bool enableOutsideTemperatureCompensation = false, bool enableCentralHeating2 = false);
+	unsigned long buildSetBoilerTemperatureRequest(float temperature);
+	unsigned long buildGetBoilerTemperatureRequest();
+	unsigned long buildSetHotWaterTemperatureRequest(float temperature);
+	unsigned long buildSlaveConfigurationRequest();
+
+
+	//responses
+	static bool isFault(unsigned long response);
+	static bool isCentralHeatingActive(unsigned long response);
+	static bool isHotWaterActive(unsigned long response);
+	static bool isFlameOn(unsigned long response);
+	static bool isCoolingActive(unsigned long response);
+	static bool isDiagnostic(unsigned long response);
+	static uint16_t getUInt(const unsigned long response);
+	static float getFloat(const unsigned long response);
+	static unsigned int temperatureToData(float temperature);
+
+	//basic requests
+	unsigned long setBoilerStatus(bool enableCentralHeating, bool enableHotWater = false, bool enableCooling = false, bool enableOutsideTemperatureCompensation = false, bool enableCentralHeating2 = false);
+	bool setBoilerTemperature(float temperature);
+	bool setHotWaterTemperature(float temperature);
+	float getBoilerTemperature();
+    float getReturnTemperature();
+    float getModulation();
+    float getPressure();
+    unsigned char getFault();
+	unsigned long getSlaveConfiguration();
+
+private:
+	const int inPin;
+	const int outPin;
+	const bool isSlave;
+
+	volatile unsigned long response;
+	volatile OpenThermResponseStatus responseStatus;
+	volatile unsigned long responseTimestamp;
+	volatile byte responseBitIndex;
+
+	int readState();
+	void setActiveState();
+	void setIdleState();
+	void activateBoiler();
+
+	void sendBit(bool high);
+	void(*handleInterruptCallback)();
+	void(*processResponseCallback)(unsigned long, int);
+};
+
+#ifndef ICACHE_RAM_ATTR
+#define ICACHE_RAM_ATTR
+#endif
+
+#endif // OpenTherm_h
\ No newline at end of file
diff --git a/tasmota/language/bg_BG.h b/tasmota/language/bg_BG.h
index 92512b1fc..6d3d6f840 100644
--- a/tasmota/language/bg_BG.h
+++ b/tasmota/language/bg_BG.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_BG_BG_H_
diff --git a/tasmota/language/cs_CZ.h b/tasmota/language/cs_CZ.h
index 6135bfa1a..cdcbf5c1b 100644
--- a/tasmota/language/cs_CZ.h
+++ b/tasmota/language/cs_CZ.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_CS_CZ_H_
diff --git a/tasmota/language/de_DE.h b/tasmota/language/de_DE.h
index 679aef391..ece6601d6 100644
--- a/tasmota/language/de_DE.h
+++ b/tasmota/language/de_DE.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "Kalibrierung fehlerhaft"
 #define D_AS3935_CAL_OK "Cap gesetzt auf:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_DE_DE_H_
diff --git a/tasmota/language/el_GR.h b/tasmota/language/el_GR.h
index f45eb3cd0..51896cab2 100644
--- a/tasmota/language/el_GR.h
+++ b/tasmota/language/el_GR.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_EL_GR_H_
diff --git a/tasmota/language/en_GB.h b/tasmota/language/en_GB.h
index 418f530c8..3af1d5bc7 100644
--- a/tasmota/language/en_GB.h
+++ b/tasmota/language/en_GB.h
@@ -794,4 +794,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_EN_GB_H_
diff --git a/tasmota/language/es_ES.h b/tasmota/language/es_ES.h
index 93553f4e6..6a83dd44e 100644
--- a/tasmota/language/es_ES.h
+++ b/tasmota/language/es_ES.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_ES_ES_H_
diff --git a/tasmota/language/fr_FR.h b/tasmota/language/fr_FR.h
index c8b7511b1..583d3ca61 100644
--- a/tasmota/language/fr_FR.h
+++ b/tasmota/language/fr_FR.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_FR_FR_H_
diff --git a/tasmota/language/he_HE.h b/tasmota/language/he_HE.h
index 37048a34f..91cb2b375 100644
--- a/tasmota/language/he_HE.h
+++ b/tasmota/language/he_HE.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_HE_HE_H_
diff --git a/tasmota/language/hu_HU.h b/tasmota/language/hu_HU.h
index 4623e2fd4..576cea8c1 100644
--- a/tasmota/language/hu_HU.h
+++ b/tasmota/language/hu_HU.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_HU_HU_H_
diff --git a/tasmota/language/it_IT.h b/tasmota/language/it_IT.h
index 806ea964e..b6b8dcacc 100644
--- a/tasmota/language/it_IT.h
+++ b/tasmota/language/it_IT.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibrazione fallita"
 #define D_AS3935_CAL_OK "calibrazione impostata a:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_IT_IT_H_
diff --git a/tasmota/language/ko_KO.h b/tasmota/language/ko_KO.h
index ca391f142..30de0b4dc 100644
--- a/tasmota/language/ko_KO.h
+++ b/tasmota/language/ko_KO.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_KO_KO_H_
diff --git a/tasmota/language/nl_NL.h b/tasmota/language/nl_NL.h
index f9d3bebf4..dd4254954 100644
--- a/tasmota/language/nl_NL.h
+++ b/tasmota/language/nl_NL.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_NL_NL_H_
diff --git a/tasmota/language/pl_PL.h b/tasmota/language/pl_PL.h
index 0b9b60b33..996a530ae 100644
--- a/tasmota/language/pl_PL.h
+++ b/tasmota/language/pl_PL.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_PL_PL_D_H_
diff --git a/tasmota/language/pt_BR.h b/tasmota/language/pt_BR.h
index 463a631d7..3f0fa6b3d 100644
--- a/tasmota/language/pt_BR.h
+++ b/tasmota/language/pt_BR.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_PT_BR_H_
diff --git a/tasmota/language/pt_PT.h b/tasmota/language/pt_PT.h
index 4dba354c9..7c8822e4d 100644
--- a/tasmota/language/pt_PT.h
+++ b/tasmota/language/pt_PT.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_PT_PT_H_
diff --git a/tasmota/language/ro_RO.h b/tasmota/language/ro_RO.h
index 850e6bac4..ea86274c9 100644
--- a/tasmota/language/ro_RO.h
+++ b/tasmota/language/ro_RO.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_RO_RO_H_
diff --git a/tasmota/language/ru_RU.h b/tasmota/language/ru_RU.h
index 127d2bfaa..0c17bfb78 100644
--- a/tasmota/language/ru_RU.h
+++ b/tasmota/language/ru_RU.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_RU_RU_H_
diff --git a/tasmota/language/sk_SK.h b/tasmota/language/sk_SK.h
index 8bddfbc11..7ed2639f9 100644
--- a/tasmota/language/sk_SK.h
+++ b/tasmota/language/sk_SK.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_SK_SK_H_
diff --git a/tasmota/language/sv_SE.h b/tasmota/language/sv_SE.h
index ea8e53129..d59ad5431 100644
--- a/tasmota/language/sv_SE.h
+++ b/tasmota/language/sv_SE.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_SV_SE_H_
diff --git a/tasmota/language/tr_TR.h b/tasmota/language/tr_TR.h
index 18918a405..2e8f72178 100644
--- a/tasmota/language/tr_TR.h
+++ b/tasmota/language/tr_TR.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_TR_TR_H_
diff --git a/tasmota/language/uk_UA.h b/tasmota/language/uk_UA.h
index 2f5026276..4749248d8 100644
--- a/tasmota/language/uk_UA.h
+++ b/tasmota/language/uk_UA.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif // _LANGUAGE_UK_UA_H_
diff --git a/tasmota/language/zh_CN.h b/tasmota/language/zh_CN.h
index 778501c18..e4244a77d 100644
--- a/tasmota/language/zh_CN.h
+++ b/tasmota/language/zh_CN.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_ZH_CN_H_
diff --git a/tasmota/language/zh_TW.h b/tasmota/language/zh_TW.h
index 6ddae8986..3398a9b87 100644
--- a/tasmota/language/zh_TW.h
+++ b/tasmota/language/zh_TW.h
@@ -793,4 +793,8 @@
 #define D_AS3935_CAL_FAIL "calibration failed"
 #define D_AS3935_CAL_OK "calibration set to:"
 
+//xsns_68_opentherm.ino
+#define D_SENSOR_BOILER_OT_RX   "OpenTherm RX"
+#define D_SENSOR_BOILER_OT_TX   "OpenTherm TX"
+
 #endif  // _LANGUAGE_ZH_TW_H_
diff --git a/tasmota/my_user_config.h b/tasmota/my_user_config.h
index ff6771a60..66b64c94f 100644
--- a/tasmota/my_user_config.h
+++ b/tasmota/my_user_config.h
@@ -666,6 +666,7 @@
   #define USE_TASMOTA_SLAVE_FLASH_SPEED 57600      // Usually 57600 for 3.3V variants and 115200 for 5V variants
   #define USE_TASMOTA_SLAVE_SERIAL_SPEED 57600     // Depends on the sketch that is running on the Uno/Pro Mini
 
+//#define USE_OPENTHERM                              // Use OpenTherm implementation
 // -- End of general directives -------------------
 
 /*********************************************************************************************\
diff --git a/tasmota/settings.h b/tasmota/settings.h
index bcbe35fa7..2a7313fd9 100644
--- a/tasmota/settings.h
+++ b/tasmota/settings.h
@@ -482,7 +482,10 @@ struct {
   uint8_t       shutter_startrelay[MAX_SHUTTERS];    // E84
   uint8_t       pcf8574_config[MAX_PCF8574];         // E88
 
-  uint8_t       free_e8c[4];               // E8C
+  uint8_t       ot_hot_water_setpoint;     // E8C
+  uint8_t       ot_boiler_setpoint;        // E8D
+  uint8_t       ot_flags;                  // E8E
+  uint8_t       free_e8f[1];               // E8F
 
   uint16_t      dimmer_hw_min;             // E90
   uint16_t      dimmer_hw_max;             // E92
diff --git a/tasmota/support_features.ino b/tasmota/support_features.ino
index aa02d676e..1fc3995a5 100644
--- a/tasmota/support_features.ino
+++ b/tasmota/support_features.ino
@@ -554,7 +554,9 @@ void GetFeatures(void)
 #ifdef USE_PING
   feature6 |= 0x00000080;  // xdrv_38_ping.ino
 #endif
-
+#ifdef USE_THERMOSTAT
+   feature6 |= 0x00000200; // xsns_68_opentherm.ino
+#endif
 //  feature6 |= 0x00000100;
 //  feature6 |= 0x00000200;
 //  feature6 |= 0x00000400;
diff --git a/tasmota/tasmota_template.h b/tasmota/tasmota_template.h
index 5f9c23b7c..fe689cc57 100644
--- a/tasmota/tasmota_template.h
+++ b/tasmota/tasmota_template.h
@@ -230,6 +230,8 @@ enum UserSelectablePins {
   GPIO_ELECTRIQ_MOODL_TX, // ElectriQ iQ-wifiMOODL Serial TX
   GPIO_AS3935,
   GPIO_PMS5003_TX,     // Plantower PMS5003 Serial interface
+  GPIO_BOILER_OT_RX,   // OpenTherm Boiler RX pin
+  GPIO_BOILER_OT_TX,   // OpenTherm Boiler TX pin
   GPIO_SENSOR_END };
 
 // Programmer selectable GPIO functionality
@@ -317,7 +319,8 @@ const char kSensorNames[] PROGMEM =
   D_SENSOR_CC1101_GDO0 "|" D_SENSOR_CC1101_GDO2 "|"
   D_SENSOR_HRXL_RX "|"
   D_SENSOR_ELECTRIQ_MOODL "|"
-  D_SENSOR_AS3935 "|" D_SENSOR_PMS5003_TX
+  D_SENSOR_AS3935 "|" D_SENSOR_PMS5003_TX "|"
+  D_SENSOR_BOILER_OT_RX "|" D_SENSOR_BOILER_OT_TX
   ;
 
 const char kSensorNamesFixed[] PROGMEM =
@@ -665,6 +668,10 @@ const uint8_t kGpioNiceList[] PROGMEM = {
 #ifdef USE_AS3935
   GPIO_AS3935,
 #endif
+#ifdef USE_OPENTHERM
+  GPIO_BOILER_OT_RX,
+  GPIO_BOILER_OT_TX,
+#endif
 };
 
 /********************************************************************************************/
diff --git a/tasmota/tasmota_template_ESP32.h b/tasmota/tasmota_template_ESP32.h
index 4aaa39ae3..874a77b78 100644
--- a/tasmota/tasmota_template_ESP32.h
+++ b/tasmota/tasmota_template_ESP32.h
@@ -125,6 +125,8 @@ enum UserSelectablePins {
   GPIO_WEBCAM_PSCLK,
   GPIO_WEBCAM_HSD,
   GPIO_WEBCAM_PSRCS,
+  GPIO_BOILER_OT_RX,   // OpenTherm Boiler RX pin
+  GPIO_BOILER_OT_TX,   // OpenTherm Boiler TX pin
   GPIO_SENSOR_END };
 
 enum ProgramSelectablePins {
@@ -211,7 +213,8 @@ const char kSensorNames[] PROGMEM =
   D_GPIO_WEBCAM_VSYNC "|" D_GPIO_WEBCAM_HREF "|" D_GPIO_WEBCAM_PCLK "|"
   D_GPIO_WEBCAM_PSCLK "|"
   D_GPIO_WEBCAM_HSD "|"
-  D_GPIO_WEBCAM_PSRCS
+  D_GPIO_WEBCAM_PSRCS "|"
+  D_SENSOR_BOILER_OT_RX "|" D_SENSOR_BOILER_OT_TX
   ;
 
 const char kSensorNamesFixed[] PROGMEM =
@@ -548,6 +551,10 @@ const uint16_t kGpioNiceList[] PROGMEM = {
 
   AGPIO(GPIO_WEBCAM_PSRCS),
 #endif
+#ifdef USE_OPENTHERM
+  AGPIO(GPIO_BOILER_OT_RX),
+  AGPIO(GPIO_BOILER_OT_TX),
+#endif
 };
 
 //********************************************************************************************
diff --git a/tasmota/xsns_68_opentherm.ino b/tasmota/xsns_68_opentherm.ino
new file mode 100644
index 000000000..953f037e5
--- /dev/null
+++ b/tasmota/xsns_68_opentherm.ino
@@ -0,0 +1,598 @@
+/*
+  xsns_68_opentherm.ino - OpenTherm protocol support for Tasmota
+
+  Copyright (C) 2020 Yuriy Sannikov
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <OpenTherm.h>
+
+#ifdef USE_OPENTHERM
+
+#define XSNS_68 68
+
+// Hot water and boiler parameter ranges
+#define OT_HOT_WATER_MIN 23
+#define OT_HOT_WATER_MAX 55
+#define OT_BOILER_MIN 40
+#define OT_BOILER_MAX 85
+
+#define OT_HOT_WATER_DEFAULT 36;
+#define OT_BOILER_DEFAULT 85;
+
+// Seconds before OT will make an attempt to connect to the boiler after connection error
+#define SNS_OT_DISCONNECT_COOLDOWN_SECONDS 10
+
+// Count of the OpenThermSettingsFlags
+#define OT_FLAGS_COUNT 6
+enum OpenThermSettingsFlags
+{
+    // If set, central heating on/off state follows diagnostic indication bit(6), however
+    // EnableCentralHeating flag has a priority over it
+    EnableCentralHeatingOnDiagnostics = 0x01,
+    // If set, DHW is on after restart.
+    EnableHotWater = 0x02,
+    // If set, keep CH always on after restart. If off, follows the EnableCentralHeatingOnDiagnostics rule
+    EnableCentralHeating = 0x04,
+    EnableCooling = 0x08,
+    EnableTemperatureCompensation = 0x10,
+    EnableCentralHeating2 = 0x20,
+};
+
+enum OpenThermConnectionStatus
+{
+    OTC_NONE,         // OT not initialized
+    OTC_DISCONNECTED, // OT communication timed out
+    OTC_CONNECTING,   // Connecting after start or from DISCONNECTED state
+    OTC_HANDSHAKE,    // Wait for the handshake response
+    OTC_READY,        // Last Known Good response state is SUCCESS and no requests are in flight
+    OTC_INFLIGHT      // Request sent, waiting from the response
+};
+
+OpenThermConnectionStatus sns_ot_connection_status = OpenThermConnectionStatus::OTC_NONE;
+uint8_t sns_ot_disconnect_cooldown = 0;
+
+OpenTherm *sns_ot_master = NULL;
+
+// Has valid values if connection status is READY or INFLIGHT
+typedef struct OT_BOILER_STATUS_T
+{
+    // Boiler fault code
+    uint8_t m_fault_code;
+    // Boiler OEM fault code
+    uint8_t m_oem_fault_code;
+    // Boilder OEM Diagnostics code
+    uint16_t m_oem_diag_code;
+    // OpenTherm ID(3) response.
+    uint8_t m_slave_flags;
+    // OpenTherm ID(1) codes. Should be used to display state
+    unsigned long m_slave_raw_status;
+    // Desired boiler states
+    bool m_enableCentralHeating;
+    bool m_enableHotWater;
+    bool m_enableCooling;
+    bool m_enableOutsideTemperatureCompensation;
+    bool m_enableCentralHeating2;
+
+    // Some boilers has an input for the heat request. When short, heat is requested
+    // OT ID(0) bit 6 may indicate state of the Heat Request input
+    // By enabling this bit we will set m_enableCentralHeating to true when OT ID(0) bit 6 is set.
+    // This enables to use external mechanical thermostat to enable heating.
+    // Some of the use cases might be setting an emergency temperature to prevent freezing
+    // in case of the software thermostat failure.
+    bool m_useDiagnosticIndicationAsHeatRequest;
+
+    // Hot Water temperature
+    float m_hotWaterSetpoint_read;
+    // Flame Modulation
+    float m_flame_modulation_read;
+    // Boiler Temperature
+    float m_boiler_temperature_read;
+
+    // Boiler desired values
+    float m_boilerSetpoint;
+    float m_hotWaterSetpoint;
+
+} OT_BOILER_STATUS;
+
+OT_BOILER_STATUS sns_ot_boiler_status;
+
+const char *sns_opentherm_connection_stat_to_str(int status)
+{
+    switch (status)
+    {
+    case OpenThermConnectionStatus::OTC_NONE:
+        return "NONE";
+    case OpenThermConnectionStatus::OTC_DISCONNECTED:
+        return "FAULT";
+    case OpenThermConnectionStatus::OTC_CONNECTING:
+        return "CONNECTING";
+    case OpenThermConnectionStatus::OTC_HANDSHAKE:
+        return "HANDSHAKE";
+    case OpenThermConnectionStatus::OTC_READY:
+        return "READY";
+    case OpenThermConnectionStatus::OTC_INFLIGHT:
+        return "BUSY";
+    default:
+        return "UNKNOWN";
+    }
+}
+
+void sns_opentherm_init_boiler_status()
+{
+    memset(&sns_ot_boiler_status, 0, sizeof(OT_BOILER_STATUS));
+
+    // Settings
+    sns_ot_boiler_status.m_useDiagnosticIndicationAsHeatRequest = Settings.ot_flags & (uint8_t)OpenThermSettingsFlags::EnableCentralHeatingOnDiagnostics;
+    sns_ot_boiler_status.m_enableHotWater = Settings.ot_flags & (uint8_t)OpenThermSettingsFlags::EnableHotWater;
+    sns_ot_boiler_status.m_enableCentralHeating = Settings.ot_flags & (uint8_t)OpenThermSettingsFlags::EnableCentralHeating;
+    sns_ot_boiler_status.m_enableCooling = Settings.ot_flags & (uint8_t)OpenThermSettingsFlags::EnableCooling;
+    sns_ot_boiler_status.m_enableOutsideTemperatureCompensation = Settings.ot_flags & (uint8_t)OpenThermSettingsFlags::EnableTemperatureCompensation;
+    sns_ot_boiler_status.m_enableCentralHeating2 = Settings.ot_flags & (uint8_t)OpenThermSettingsFlags::EnableCentralHeating2;
+
+    sns_ot_boiler_status.m_boilerSetpoint = (float)Settings.ot_boiler_setpoint;
+    sns_ot_boiler_status.m_hotWaterSetpoint = (float)Settings.ot_hot_water_setpoint;
+
+    sns_ot_boiler_status.m_fault_code = 0;
+    sns_ot_boiler_status.m_oem_fault_code = 0;
+    sns_ot_boiler_status.m_oem_diag_code = 0;
+    sns_ot_boiler_status.m_hotWaterSetpoint_read = 0;
+    sns_ot_boiler_status.m_flame_modulation_read = 0;
+    sns_ot_boiler_status.m_boiler_temperature_read = 0;
+}
+
+void ICACHE_RAM_ATTR sns_opentherm_handleInterrupt()
+{
+    sns_ot_master->handleInterrupt();
+}
+
+void sns_opentherm_processResponseCallback(unsigned long response, int st)
+{
+    OpenThermResponseStatus status = (OpenThermResponseStatus)st;
+    AddLog_P2(LOG_LEVEL_DEBUG_MORE,
+              PSTR("[OTH]: Processing response. Status=%s, Response=0x%lX"),
+              sns_ot_master->statusToString(status), response);
+
+    if (sns_ot_connection_status == OpenThermConnectionStatus::OTC_HANDSHAKE)
+    {
+        return sns_ot_process_handshake(response, st);
+    }
+
+    switch (status)
+    {
+    case OpenThermResponseStatus::SUCCESS:
+        if (sns_ot_master->isValidResponse(response))
+        {
+            sns_opentherm_process_success_response(&sns_ot_boiler_status, response);
+        }
+        sns_ot_connection_status = OpenThermConnectionStatus::OTC_READY;
+        break;
+
+    case OpenThermResponseStatus::INVALID:
+        sns_opentherm_check_retry_request();
+        sns_ot_connection_status = OpenThermConnectionStatus::OTC_READY;
+        break;
+
+    // Timeout may indicate not valid/supported command or connection error
+    // In this case we do reconnect.
+    // If this command will timeout multiple times, it will be excluded from the rotation later on
+    // after couple of failed attempts. See sns_opentherm_check_retry_request logic
+    case OpenThermResponseStatus::TIMEOUT:
+        sns_opentherm_check_retry_request();
+        sns_ot_connection_status = OpenThermConnectionStatus::OTC_DISCONNECTED;
+        break;
+    }
+}
+
+bool sns_opentherm_Init()
+{
+    if (PinUsed(GPIO_BOILER_OT_RX) && PinUsed(GPIO_BOILER_OT_TX))
+    {
+        sns_ot_master = new OpenTherm(Pin(GPIO_BOILER_OT_RX), Pin(GPIO_BOILER_OT_TX));
+        sns_ot_master->begin(sns_opentherm_handleInterrupt, sns_opentherm_processResponseCallback);
+        sns_ot_connection_status = OpenThermConnectionStatus::OTC_CONNECTING;
+
+        sns_opentherm_init_boiler_status();
+        return true;
+    }
+    return false;
+    // !warning, sns_opentherm settings are not ready at this point
+}
+
+void sns_opentherm_stat(bool json)
+{
+    if (!sns_ot_master)
+    {
+        return;
+    }
+    const char *statusStr = sns_opentherm_connection_stat_to_str(sns_ot_connection_status);
+
+    if (json)
+    {
+        ResponseAppend_P(PSTR(",\"OPENTHERM\":{"));
+        ResponseAppend_P(PSTR("\"conn\":\"%s\","), statusStr);
+        ResponseAppend_P(PSTR("\"settings\":%d,"), Settings.ot_flags);
+        sns_opentherm_dump_telemetry();
+        ResponseJsonEnd();
+#ifdef USE_WEBSERVER
+    }
+    else
+    {
+        WSContentSend_P(PSTR("{s}OpenTherm status{m}%s (0x%X){e}"), statusStr, (int)sns_ot_boiler_status.m_slave_flags);
+        if (sns_ot_connection_status < OpenThermConnectionStatus::OTC_READY)
+        {
+            return;
+        }
+        WSContentSend_P(PSTR("{s}Std/OEM Fault Codes{m}%d / %d{e}"),
+                        (int)sns_ot_boiler_status.m_fault_code,
+                        (int)sns_ot_boiler_status.m_oem_fault_code);
+
+        WSContentSend_P(PSTR("{s}OEM Diagnostic Code{m}%d{e}"),
+                        (int)sns_ot_boiler_status.m_oem_diag_code);
+
+        WSContentSend_P(PSTR("{s}Hot Water Setpoint{m}%d{e}"),
+                        (int)sns_ot_boiler_status.m_hotWaterSetpoint_read);
+
+        WSContentSend_P(PSTR("{s}Flame Modulation{m}%d{e}"),
+                        (int)sns_ot_boiler_status.m_flame_modulation_read);
+
+        WSContentSend_P(PSTR("{s}Boiler Temp/Setpnt{m}%d / %d{e}"),
+                        (int)sns_ot_boiler_status.m_boiler_temperature_read,
+                        (int)sns_ot_boiler_status.m_boilerSetpoint);
+
+        if (OpenTherm::isCentralHeatingActive(sns_ot_boiler_status.m_slave_raw_status))
+        {
+            WSContentSend_P(PSTR("{s}Central Heating is ACTIVE{m}{e}"));
+        }
+
+        if (sns_ot_boiler_status.m_enableHotWater)
+        {
+            WSContentSend_P(PSTR("{s}Hot Water is Enabled{m}{e}"));
+        }
+
+        if (OpenTherm::isHotWaterActive(sns_ot_boiler_status.m_slave_raw_status))
+        {
+            WSContentSend_P(PSTR("{s}Hot Water is ACTIVE{m}{e}"));
+        }
+
+        if (OpenTherm::isFlameOn(sns_ot_boiler_status.m_slave_raw_status))
+        {
+            WSContentSend_P(PSTR("{s}Flame is ACTIVE{m}{e}"));
+        }
+
+        if (sns_ot_boiler_status.m_enableCooling)
+        {
+            WSContentSend_P(PSTR("{s}Cooling is Enabled{m}{e}"));
+        }
+
+        if (OpenTherm::isCoolingActive(sns_ot_boiler_status.m_slave_raw_status))
+        {
+            WSContentSend_P(PSTR("{s}Cooling is ACTIVE{m}{e}"));
+        }
+
+        if (OpenTherm::isDiagnostic(sns_ot_boiler_status.m_slave_raw_status))
+        {
+            WSContentSend_P(PSTR("{s}Diagnostic Indication{m}{e}"));
+        }
+
+#endif // USE_WEBSERVER
+    }
+}
+
+void sns_ot_start_handshake()
+{
+    if (!sns_ot_master)
+    {
+        return;
+    }
+
+    AddLog_P2(LOG_LEVEL_DEBUG, PSTR("[OTH]: perform handshake"));
+
+    sns_ot_master->sendRequestAync(
+        OpenTherm::buildRequest(OpenThermMessageType::READ_DATA, OpenThermMessageID::SConfigSMemberIDcode, 0));
+
+    sns_ot_connection_status = OpenThermConnectionStatus::OTC_HANDSHAKE;
+}
+
+void sns_ot_process_handshake(unsigned long response, int st)
+{
+    OpenThermResponseStatus status = (OpenThermResponseStatus)st;
+
+    if (status != OpenThermResponseStatus::SUCCESS || !sns_ot_master->isValidResponse(response))
+    {
+        AddLog_P2(LOG_LEVEL_ERROR,
+                  PSTR("[OTH]: getSlaveConfiguration failed. Status=%s"),
+                  sns_ot_master->statusToString(status));
+        sns_ot_connection_status = OpenThermConnectionStatus::OTC_DISCONNECTED;
+        return;
+    }
+
+    AddLog_P2(LOG_LEVEL_DEBUG, PSTR("[OTH]: getLastResponseStatus SUCCESS. Slave Cfg: %lX"), response);
+
+    sns_ot_boiler_status.m_slave_flags = (response & 0xFF00) >> 8;
+
+    sns_ot_connection_status = OpenThermConnectionStatus::OTC_READY;
+}
+
+void sns_opentherm_CheckSettings(void)
+{
+    bool settingsValid = true;
+
+    settingsValid &= Settings.ot_hot_water_setpoint >= OT_HOT_WATER_MIN;
+    settingsValid &= Settings.ot_hot_water_setpoint <= OT_HOT_WATER_MAX;
+    settingsValid &= Settings.ot_boiler_setpoint >= OT_BOILER_MIN;
+    settingsValid &= Settings.ot_boiler_setpoint <= OT_BOILER_MAX;
+
+    if (!settingsValid)
+    {
+        Settings.ot_hot_water_setpoint = OT_HOT_WATER_DEFAULT;
+        Settings.ot_boiler_setpoint = OT_BOILER_DEFAULT;
+        Settings.ot_flags =
+            OpenThermSettingsFlags::EnableCentralHeatingOnDiagnostics |
+            OpenThermSettingsFlags::EnableHotWater;
+    }
+}
+/*********************************************************************************************\
+ * Command Processing
+\*********************************************************************************************/
+const char *sns_opentherm_flag_text(uint8_t mode)
+{
+    switch ((OpenThermSettingsFlags)mode)
+    {
+    case OpenThermSettingsFlags::EnableCentralHeatingOnDiagnostics:
+        return "CHOD";
+    case OpenThermSettingsFlags::EnableHotWater:
+        return "DHW";
+    case OpenThermSettingsFlags::EnableCentralHeating:
+        return "CH";
+    case OpenThermSettingsFlags::EnableCooling:
+        return "COOL";
+    case OpenThermSettingsFlags::EnableTemperatureCompensation:
+        return "OTC";
+    case OpenThermSettingsFlags::EnableCentralHeating2:
+        return "CH2";
+    default:
+        return "?";
+    }
+}
+
+uint8_t sns_opentherm_parse_flag(char *flag)
+{
+    if (!strncmp(flag, "CHOD", 4))
+    {
+        return OpenThermSettingsFlags::EnableCentralHeatingOnDiagnostics;
+    }
+    else if (!strncmp(flag, "COOL", 4))
+    {
+        return OpenThermSettingsFlags::EnableCooling;
+    }
+    else if (!strncmp(flag, "DHW", 3))
+    {
+        return OpenThermSettingsFlags::EnableHotWater;
+    }
+    else if (!strncmp(flag, "OTC", 3))
+    {
+        return OpenThermSettingsFlags::EnableTemperatureCompensation;
+    }
+    else if (!strncmp(flag, "CH2", 3))
+    {
+        return OpenThermSettingsFlags::EnableCentralHeating2;
+    }
+    else if (!strncmp(flag, "CH", 2))
+    {
+        return OpenThermSettingsFlags::EnableCentralHeating;
+    }
+    return 0;
+}
+
+uint8_t sns_opentherm_read_flags(char *data, uint32_t len)
+{
+    uint8_t tokens = 1;
+    for (int i = 0; i < len; ++i)
+    {
+        if (data[i] == ',')
+        {
+            ++tokens;
+        }
+    }
+    uint8_t result = 0;
+    char sub_string[XdrvMailbox.data_len + 1];
+    for (int i = 1; i <= tokens; ++i)
+    {
+        char *flag = subStr(sub_string, data, ",", i);
+        if (!flag)
+        {
+            break;
+        }
+        result |= sns_opentherm_parse_flag(flag);
+    }
+    return result;
+}
+#define D_PRFX_OTHERM "ot_"
+// set the boiler temperature (CH). Sutable for the PID app.
+// After restart will use the defaults from the settings
+#define D_CMND_OTHERM_BOILER_SETPOINT "tboiler"
+// set hot water (DHW) temperature. Do not write it in the flash memory.
+// suitable for the temporary changes
+#define D_CMND_OTHERM_DHW_SETPOINT "twater"
+// This command will save CH and DHW setpoints into the settings. Those values will be used after system restart
+// The reason to separate set and save is to reduce flash memory write count, especially if boiler temperature is controlled
+// by the PID thermostat
+#define D_CMND_OTHERM_SAVE_SETTINGS "save_setpoints"
+// Get or set flags
+
+// EnableCentralHeatingOnDiagnostics -> CHOD
+// EnableHotWater                    -> DHW
+// EnableCentralHeating              -> CH
+// EnableCooling                     -> COOL
+// EnableTemperatureCompensation     -> OTC
+// EnableCentralHeating2             -> CH2
+#define D_CMND_OTHERM_FLAGS "flags"
+
+// Get/Set boiler status m_enableCentralHeating value. It's equivalent of the EnableCentralHeating settings
+// flag value, however, this command does not update the settings.
+// Usefull to buld automations
+// Please note, if you set it to "0" and EnableCentralHeatingOnDiagnostics is set
+// boiler will follow the Diagnostics bit and won't turn CH off. When Diagnostics bit cleared,
+// and "ot_ch" is "1", boiler will keep heating
+#define D_CMND_SET_CENTRAL_HEATING_ENABLED "ch"
+
+const char kOpenThermCommands[] PROGMEM = D_PRFX_OTHERM "|" D_CMND_OTHERM_BOILER_SETPOINT "|" D_CMND_OTHERM_DHW_SETPOINT
+    "|" D_CMND_OTHERM_SAVE_SETTINGS "|" D_CMND_OTHERM_FLAGS "|" D_CMND_SET_CENTRAL_HEATING_ENABLED;
+
+void (*const OpenThermCommands[])(void) PROGMEM = {
+    &sns_opentherm_boiler_setpoint_cmd,
+    &sns_opentherm_hot_water_setpoint_cmd,
+    &sns_opentherm_save_settings_cmd,
+    &sns_opentherm_flags_cmd,
+    &sns_opentherm_set_central_heating_cmd};
+
+void sns_opentherm_cmd(void) { }
+void sns_opentherm_boiler_setpoint_cmd(void)
+{
+    bool query = strlen(XdrvMailbox.data) == 0;
+    if (!query)
+    {
+        sns_ot_boiler_status.m_boilerSetpoint = atof(XdrvMailbox.data);
+    }
+    ResponseCmndFloat(sns_ot_boiler_status.m_boilerSetpoint, Settings.flag2.temperature_resolution);
+}
+
+void sns_opentherm_hot_water_setpoint_cmd(void)
+{
+    bool query = strlen(XdrvMailbox.data) == 0;
+    if (!query)
+    {
+        sns_ot_boiler_status.m_hotWaterSetpoint = atof(XdrvMailbox.data);
+    }
+    ResponseCmndFloat(sns_ot_boiler_status.m_hotWaterSetpoint, Settings.flag2.temperature_resolution);
+}
+
+void sns_opentherm_save_settings_cmd(void)
+{
+    Settings.ot_hot_water_setpoint = (uint8_t)sns_ot_boiler_status.m_hotWaterSetpoint;
+    Settings.ot_boiler_setpoint = (uint8_t)sns_ot_boiler_status.m_boilerSetpoint;
+    ResponseCmndDone();
+}
+
+void sns_opentherm_flags_cmd(void)
+{
+    bool query = strlen(XdrvMailbox.data) == 0;
+    if (!query)
+    {
+        // Set flags value
+        Settings.ot_flags = sns_opentherm_read_flags(XdrvMailbox.data, XdrvMailbox.data_len);
+        // Reset boiler status to apply settings
+        sns_opentherm_init_boiler_status();
+    }
+    bool addComma = false;
+    mqtt_data[0] = 0;
+    for (int pos = 0; pos < OT_FLAGS_COUNT; ++pos)
+    {
+        int mask = 1 << pos;
+        int mode = Settings.ot_flags & (uint8_t)mask;
+        if (mode > 0)
+        {
+            if (addComma)
+            {
+                snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("%s,"), mqtt_data);
+            }
+            snprintf_P(mqtt_data, sizeof(mqtt_data), PSTR("%s%s"), mqtt_data, sns_opentherm_flag_text(mode));
+            addComma = true;
+        }
+    }
+}
+
+void sns_opentherm_set_central_heating_cmd(void)
+{
+    bool query = strlen(XdrvMailbox.data) == 0;
+    if (!query)
+    {
+        sns_ot_boiler_status.m_enableCentralHeating = atoi(XdrvMailbox.data);
+    }
+    ResponseCmndNumber(sns_ot_boiler_status.m_enableCentralHeating ? 1 : 0);
+}
+
+/*********************************************************************************************\
+ * Interface
+\*********************************************************************************************/
+
+bool Xsns68(uint8_t function)
+{
+    bool result = false;
+    if (FUNC_INIT == function)
+    {
+        if (sns_opentherm_Init())
+        {
+            sns_opentherm_CheckSettings();
+        }
+    }
+
+    if (!sns_ot_master)
+    {
+        return result;
+    }
+
+    switch (function)
+    {
+    case FUNC_LOOP:
+        sns_ot_master->process();
+        break;
+    case FUNC_EVERY_100_MSECOND:
+        if (sns_ot_connection_status == OpenThermConnectionStatus::OTC_READY && sns_ot_master->isReady())
+        {
+            unsigned long request = sns_opentherm_get_next_request(&sns_ot_boiler_status);
+            if (-1 != request)
+            {
+                sns_ot_master->sendRequestAync(request);
+                sns_ot_connection_status = OpenThermConnectionStatus::OTC_INFLIGHT;
+            }
+        }
+        break;
+    case FUNC_EVERY_SECOND:
+        if (sns_ot_connection_status == OpenThermConnectionStatus::OTC_DISCONNECTED)
+        {
+            // If disconnected, wait for the SNS_OT_DISCONNECT_COOLDOWN_SECONDS before the handshake
+            if (sns_ot_disconnect_cooldown == 0)
+            {
+                sns_ot_disconnect_cooldown = SNS_OT_DISCONNECT_COOLDOWN_SECONDS;
+            }
+            else if (--sns_ot_disconnect_cooldown == 0)
+            {
+                sns_ot_connection_status = OpenThermConnectionStatus::OTC_CONNECTING;
+            }
+        }
+        else if (sns_ot_connection_status == OpenThermConnectionStatus::OTC_CONNECTING)
+        {
+            sns_ot_start_handshake();
+        }
+        break;
+    case FUNC_COMMAND:
+        result = DecodeCommand(kOpenThermCommands, OpenThermCommands);
+        break;
+    case FUNC_JSON_APPEND:
+        sns_opentherm_stat(1);
+        break;
+#ifdef USE_WEBSERVER
+    case FUNC_WEB_SENSOR:
+        sns_opentherm_stat(0);
+        break;
+#endif // USE_WEBSERVER
+    }
+
+    return result;
+}
+
+#endif // USE_OPENTHERM
diff --git a/tasmota/xsns_68_opentherm_protocol.ino b/tasmota/xsns_68_opentherm_protocol.ino
new file mode 100644
index 000000000..2693b086c
--- /dev/null
+++ b/tasmota/xsns_68_opentherm_protocol.ino
@@ -0,0 +1,440 @@
+/*
+  xsns_68_opentherm_protocol.ino - OpenTherm protocol support for Tasmota
+
+  Copyright (C) 2020 Yuriy Sannikov
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "OpenTherm.h"
+
+#ifdef USE_OPENTHERM
+
+// Temperature tolerance. If temperature setpoint difference is less than the value,
+// OT (1)(Control setpoint) command will be skipped
+#define OPENTHERM_BOILER_SETPOINT_TOLERANCE 1.0
+
+typedef union {
+    uint8_t m_flags;
+    struct
+    {
+        uint8_t notSupported : 1; // If set, boiler does not support this command
+        uint8_t supported : 1;    // Set if at least one response were successfull
+        uint8_t retryCount : 2;   // Retry counter before notSupported flag being set
+    };
+} OpenThermParamFlags;
+
+typedef union {
+    float m_float;
+    uint8_t m_u8;
+    uint16_t m_u16;
+    unsigned long m_ul;
+    bool m_bool;
+} ResponseStorage;
+
+typedef struct OpenThermCommandT
+{
+    const char *m_command_name;
+    uint8_t m_command_code;
+    OpenThermParamFlags m_flags;
+    ResponseStorage m_results[2];
+    unsigned long (*m_ot_make_request)(OpenThermCommandT *self, OT_BOILER_STATUS_T *boilerStatus);
+    void (*m_ot_parse_response)(OpenThermCommandT *self, OT_BOILER_STATUS_T *boilerStatus, unsigned long response);
+    void (*m_ot_appent_telemetry)(OpenThermCommandT *self);
+} OpenThermCommand;
+
+OpenThermCommand sns_opentherm_commands[] = {
+    {// Get/Set Slave Status Flags
+     .m_command_name = "SLAVE",
+     .m_command_code = 0,
+     // OpenTherm ID(0) should never go into the notSupported state due to some connectivity issues
+     // otherwice it may lose boiler control
+     .m_flags = {.supported = 1},
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_set_slave_flags,
+     .m_ot_parse_response = sns_opentherm_parse_slave_flags,
+     .m_ot_appent_telemetry = sns_opentherm_tele_slave_flags},
+    {// Set boiler temperature
+     .m_command_name = "BTMP",
+     .m_command_code = 0,
+     // OpenTherm ID(1) also should never go into the notSupported state due to some connectivity issues
+     .m_flags = {.supported = 1},
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_set_boiler_temperature,
+     .m_ot_parse_response = sns_opentherm_parse_set_boiler_temperature,
+     .m_ot_appent_telemetry = sns_opentherm_tele_boiler_temperature},
+    {// Set Hot Water temperature
+     .m_command_name = "HWTMP",
+     .m_command_code = 0,
+     // OpenTherm ID(56) may not be supported
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_set_boiler_dhw_temperature,
+     .m_ot_parse_response = sns_opentherm_parse_boiler_dhw_temperature,
+     .m_ot_appent_telemetry = sns_opentherm_tele_boiler_dhw_temperature},
+    {// Read Application-specific fault flags and OEM fault code
+     .m_command_name = "ASFF",
+     .m_command_code = 0,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_flags,
+     .m_ot_parse_response = sns_opentherm_parse_flags,
+     .m_ot_appent_telemetry = sns_opentherm_tele_flags},
+    {// Read An OEM-specific diagnostic/service code
+     .m_command_name = "OEMD",
+     .m_command_code = 0,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_oem_diag,
+     .m_ot_parse_response = sns_opentherm_parse_oem_diag,
+     .m_ot_appent_telemetry = sns_opentherm_tele_oem_diag},
+    {// Read Flame modulation
+     .m_command_name = "FLM",
+     .m_command_code = (uint8_t)OpenThermMessageID::RelModLevel,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_flame_modulation,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+    {// Read Boiler Temperature
+     .m_command_name = "TB",
+     .m_command_code = (uint8_t)OpenThermMessageID::Tboiler,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_boiler_temperature,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+    {// Read DHW temperature
+     .m_command_name = "TDHW",
+     .m_command_code = (uint8_t)OpenThermMessageID::Tdhw,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_generic_float,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+    {// Read Outside temperature
+     .m_command_name = "TOUT",
+     .m_command_code = (uint8_t)OpenThermMessageID::Toutside,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_generic_float,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+    {// Read Return water temperature
+     .m_command_name = "TRET",
+     .m_command_code = (uint8_t)OpenThermMessageID::Tret,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_generic_float,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+    {// Read DHW setpoint
+     .m_command_name = "DHWS",
+     .m_command_code = (uint8_t)OpenThermMessageID::TdhwSet,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_dhw_setpoint,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+    {// Read max CH water setpoint
+     .m_command_name = "TMAX",
+     .m_command_code = (uint8_t)OpenThermMessageID::MaxTSet,
+     .m_flags = 0,
+     .m_results = {{.m_u8 = 0}, {.m_u8 = 0}},
+     .m_ot_make_request = sns_opentherm_get_generic_float,
+     .m_ot_parse_response = sns_opentherm_parse_generic_float,
+     .m_ot_appent_telemetry = sns_opentherm_tele_generic_float},
+
+};
+
+/////////////////////////////////// Process Slave Status Flags & Control //////////////////////////////////////////////////
+unsigned long sns_opentherm_set_slave_flags(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *status)
+{
+    bool centralHeatingIsOn = status->m_enableCentralHeating;
+
+    if (status->m_useDiagnosticIndicationAsHeatRequest) {
+        centralHeatingIsOn |= OpenTherm::isDiagnostic(status->m_slave_raw_status);
+    }
+
+    if (self->m_results[1].m_bool != centralHeatingIsOn) {
+        AddLog_P2(LOG_LEVEL_INFO,
+            PSTR("[OTH]: Central Heating transitioning from %s to %s"),
+            self->m_results[1].m_bool ? "on" : "off",
+            status->m_enableCentralHeating ? "on" : "off");
+    }
+    self->m_results[1].m_bool = centralHeatingIsOn;
+
+    unsigned int data = centralHeatingIsOn |
+                        (status->m_enableHotWater << 1) |
+                        (status->m_enableCooling << 2) |
+                        (status->m_enableOutsideTemperatureCompensation << 3) |
+                        (status->m_enableCentralHeating2 << 4);
+
+    data <<= 8;
+
+    return OpenTherm::buildRequest(OpenThermRequestType::READ, OpenThermMessageID::Status, data);
+}
+
+void sns_opentherm_parse_slave_flags(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    boilerStatus->m_slave_raw_status = response;
+    self->m_results[0].m_ul = response;
+}
+
+#define OT_FLAG_TO_ON_OFF(status, flag) ((((status) & (flag)) != 0) ? 1 : 0)
+void sns_opentherm_tele_slave_flags(struct OpenThermCommandT *self)
+{
+    unsigned long st = self->m_results[0].m_ul;
+    ResponseAppend_P(PSTR("{\"FAULT\":%d,\"CH\":%d,\"DHW\":%d,\"FL\":%d,\"COOL\":%d,\"CH2\":%d,\"DIAG\":%d,\"RAW\":%lu}"),
+                     OT_FLAG_TO_ON_OFF(st, 0x01),
+                     OT_FLAG_TO_ON_OFF(st, 0x02),
+                     OT_FLAG_TO_ON_OFF(st, 0x04),
+                     OT_FLAG_TO_ON_OFF(st, 0x08),
+                     OT_FLAG_TO_ON_OFF(st, 0x10),
+                     OT_FLAG_TO_ON_OFF(st, 0x20),
+                     OT_FLAG_TO_ON_OFF(st, 0x40),
+                     st);
+}
+
+/////////////////////////////////// Set Boiler Temperature //////////////////////////////////////////////////
+unsigned long sns_opentherm_set_boiler_temperature(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *status)
+{
+    // Assuming some boilers might write setpoint temperature into the Flash memory
+    // Having PID controlled appliance may produce a lot of small fluctuations in the setpoint value
+    // wearing out Boiler flash memory.
+    float diff = abs(status->m_boilerSetpoint - self->m_results[0].m_float);
+    // Ignore small changes in the boiler setpoint temperature
+    if (diff < OPENTHERM_BOILER_SETPOINT_TOLERANCE)
+    {
+        return -1;
+    }
+    AddLog_P2(LOG_LEVEL_INFO,
+              PSTR("[OTH]: Setting Boiler Temp. Old: %d, New: %d"),
+              (int)self->m_results[0].m_float,
+              (int)status->m_boilerSetpoint);
+    self->m_results[0].m_float = status->m_boilerSetpoint;
+
+    unsigned int data = OpenTherm::temperatureToData(status->m_boilerSetpoint);
+    return OpenTherm::buildRequest(OpenThermMessageType::WRITE_DATA, OpenThermMessageID::TSet, data);
+}
+void sns_opentherm_parse_set_boiler_temperature(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    self->m_results[1].m_float = OpenTherm::getFloat(response);
+}
+void sns_opentherm_tele_boiler_temperature(struct OpenThermCommandT *self)
+{
+    char requested[FLOATSZ];
+    dtostrfd(self->m_results[0].m_float, Settings.flag2.temperature_resolution, requested);
+    char actual[FLOATSZ];
+    dtostrfd(self->m_results[1].m_float, Settings.flag2.temperature_resolution, actual);
+
+    // indicate fault if tepmerature demand and actual setpoint are greater then tolerance
+    bool isFault = abs(self->m_results[1].m_float - self->m_results[0].m_float) > OPENTHERM_BOILER_SETPOINT_TOLERANCE;
+
+    ResponseAppend_P(PSTR("{\"FAULT\":%d,\"REQ\":%s,\"ACT\": %s}"),
+                     (int)isFault,
+                     requested,
+                     actual);
+}
+
+/////////////////////////////////// Set Domestic Hot Water Temperature //////////////////////////////////////////////////
+unsigned long sns_opentherm_set_boiler_dhw_temperature(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *status)
+{
+    // The same consideration as for the boiler temperature
+    float diff = abs(status->m_hotWaterSetpoint - self->m_results[0].m_float);
+    // Ignore small changes in the boiler setpoint temperature
+    if (diff < OPENTHERM_BOILER_SETPOINT_TOLERANCE)
+    {
+        return -1;
+    }
+    AddLog_P2(LOG_LEVEL_INFO,
+              PSTR("[OTH]: Setting Hot Water Temp. Old: %d, New: %d"),
+              (int)self->m_results[0].m_float,
+              (int)status->m_hotWaterSetpoint);
+
+    self->m_results[0].m_float = status->m_hotWaterSetpoint;
+
+    unsigned int data = OpenTherm::temperatureToData(status->m_hotWaterSetpoint);
+    return OpenTherm::buildRequest(OpenThermMessageType::WRITE_DATA, OpenThermMessageID::TdhwSet, data);
+}
+void sns_opentherm_parse_boiler_dhw_temperature(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    self->m_results[1].m_float = OpenTherm::getFloat(response);
+}
+void sns_opentherm_tele_boiler_dhw_temperature(struct OpenThermCommandT *self)
+{
+    char requested[FLOATSZ];
+    dtostrfd(self->m_results[0].m_float, Settings.flag2.temperature_resolution, requested);
+    char actual[FLOATSZ];
+    dtostrfd(self->m_results[1].m_float, Settings.flag2.temperature_resolution, actual);
+
+    ResponseAppend_P(PSTR("{\"REQ\":%s,\"ACT\": %s}"),
+                     requested,
+                     actual);
+}
+
+/////////////////////////////////// App Specific Fault Flags //////////////////////////////////////////////////
+unsigned long sns_opentherm_get_flags(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *)
+{
+    return OpenTherm::buildRequest(OpenThermRequestType::READ, OpenThermMessageID::ASFflags, 0);
+}
+
+void sns_opentherm_parse_flags(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    uint8_t fault_code = (response >> 8) & 0xFF;
+    uint8_t oem_fault_code = response & 0xFF;
+    boilerStatus->m_fault_code = fault_code;
+    boilerStatus->m_oem_fault_code = fault_code;
+    self->m_results[0].m_u8 = fault_code;
+    self->m_results[1].m_u8 = oem_fault_code;
+}
+
+void sns_opentherm_tele_flags(struct OpenThermCommandT *self)
+{
+    ResponseAppend_P(PSTR("{\"FC\":%d,\"OFC\":%d}"),
+                     (int)self->m_results[0].m_u8,
+                     (int)self->m_results[1].m_u8);
+}
+
+/////////////////////////////////// OEM Diag Code //////////////////////////////////////////////////
+unsigned long sns_opentherm_get_oem_diag(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *)
+{
+    return OpenTherm::buildRequest(OpenThermRequestType::READ, OpenThermMessageID::OEMDiagnosticCode, 0);
+}
+
+void sns_opentherm_parse_oem_diag(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    uint16_t diag_code = (uint16_t)response & 0xFFFF;
+    boilerStatus->m_oem_diag_code = diag_code;
+    self->m_results[0].m_u16 = diag_code;
+}
+
+void sns_opentherm_tele_oem_diag(struct OpenThermCommandT *self)
+{
+    ResponseAppend_P(PSTR("%d"), (int)self->m_results[0].m_u16);
+}
+
+/////////////////////////////////// Generic Single Float /////////////////////////////////////////////////
+unsigned long sns_opentherm_get_generic_float(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *)
+{
+    return OpenTherm::buildRequest(OpenThermRequestType::READ, (OpenThermMessageID)self->m_command_code, 0);
+}
+
+void sns_opentherm_parse_generic_float(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    self->m_results[0].m_float = OpenTherm::getFloat(response);
+}
+
+void sns_opentherm_tele_generic_float(struct OpenThermCommandT *self)
+{
+    char str[FLOATSZ];
+    dtostrfd(self->m_results[0].m_float, Settings.flag2.temperature_resolution, str);
+    ResponseAppend_P(PSTR("%s"), str);
+}
+
+/////////////////////////////////// Specific Floats Rerports to the  /////////////////////////////////////////////////
+void sns_opentherm_parse_dhw_setpoint(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    self->m_results[0].m_float = OpenTherm::getFloat(response);
+    boilerStatus->m_hotWaterSetpoint_read = self->m_results[0].m_float;
+}
+
+void sns_opentherm_parse_flame_modulation(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    self->m_results[0].m_float = OpenTherm::getFloat(response);
+    boilerStatus->m_flame_modulation_read = self->m_results[0].m_float;
+}
+
+void sns_opentherm_parse_boiler_temperature(struct OpenThermCommandT *self, struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    self->m_results[0].m_float = OpenTherm::getFloat(response);
+    boilerStatus->m_boiler_temperature_read = self->m_results[0].m_float;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+#define SNS_OT_COMMANDS_COUNT (sizeof(sns_opentherm_commands) / sizeof(OpenThermCommand))
+int sns_opentherm_current_command = SNS_OT_COMMANDS_COUNT;
+
+unsigned long sns_opentherm_get_next_request(struct OT_BOILER_STATUS_T *boilerStatus)
+{
+    // get next and loop the command
+    if (++sns_opentherm_current_command >= SNS_OT_COMMANDS_COUNT)
+    {
+        sns_opentherm_current_command = 0;
+    }
+
+    struct OpenThermCommandT *cmd = &sns_opentherm_commands[sns_opentherm_current_command];
+    // Return error if command known as not supported
+    if (cmd->m_flags.notSupported)
+    {
+        return -1;
+    }
+    // Retrurn OT compatible request
+    return cmd->m_ot_make_request(cmd, boilerStatus);
+}
+
+void sns_opentherm_check_retry_request()
+{
+    if (sns_opentherm_current_command >= SNS_OT_COMMANDS_COUNT)
+    {
+        return;
+    }
+    struct OpenThermCommandT *cmd = &sns_opentherm_commands[sns_opentherm_current_command];
+
+    bool canRetry = ++cmd->m_flags.retryCount < 3;
+    // In case of last retry and if this command never respond successfully, set notSupported flag
+    if (!canRetry && !cmd->m_flags.supported)
+    {
+        cmd->m_flags.notSupported = true;
+        AddLog_P2(LOG_LEVEL_ERROR,
+                  PSTR("[OTH]: command %s is not supported by the boiler. Last status: %s"),
+                  cmd->m_command_name,
+                  sns_ot_master->statusToString(sns_ot_master->getLastResponseStatus()));
+    }
+}
+
+void sns_opentherm_process_success_response(struct OT_BOILER_STATUS_T *boilerStatus, unsigned long response)
+{
+    if (sns_opentherm_current_command >= SNS_OT_COMMANDS_COUNT)
+    {
+        return;
+    }
+    struct OpenThermCommandT *cmd = &sns_opentherm_commands[sns_opentherm_current_command];
+    // mark command as supported
+    cmd->m_flags.supported = true;
+
+    cmd->m_ot_parse_response(cmd, boilerStatus, response);
+}
+
+void sns_opentherm_dump_telemetry()
+{
+    bool add_coma = false;
+    for (int i = 0; i < SNS_OT_COMMANDS_COUNT; ++i)
+    {
+        struct OpenThermCommandT *cmd = &sns_opentherm_commands[i];
+        if (!cmd->m_flags.supported)
+        {
+            continue;
+        }
+
+        ResponseAppend_P(PSTR("%s\"%s\":"), add_coma ? "," : "", cmd->m_command_name);
+
+        cmd->m_ot_appent_telemetry(cmd);
+
+        add_coma = true;
+    }
+}
+#endif
\ No newline at end of file