Try
Serial.print("<- ");
OPENTHERM::printToSerial(message);
Serial.print(" ");
Serial.print(message.f88());
Serial.println();
Not tested or even compiled.
Try
Serial.print("<- ");
OPENTHERM::printToSerial(message);
Serial.print(" ");
Serial.print(message.f88());
Serial.println();
Not tested or even compiled.