This project is based on http://ihormelnyk.com/page/arduino_opentherm_controller. I made some little upgrades and created library.
Interface of library is:
// setup pins
void setupOT();
void activateOT();
// send request and read response
uint32_t sendRequest(uint32_t request);
// print formated - DEBUG on Serial
void printRequest(uint32_t request);
void printResponse(uint32_t request);
void printBinary(uint32_t val);
// create Opentherm datagram from msgType, dataID and dataValue
uint32_t makeOTDataBlock(uint8_t msgType, uint8_t dataID, uint16_t dataValue);
// convert float number to Opentherm coding
int16_t floatToOT16 (float in);
// convert Opentherm coding to float number
float OT16ToFloat (int16_t in);