void RobotControl::readCO2Sensor(int &c){
  c = -9999;  //default returned value in case of problem of connection
  messageOut.writeByte(COMMAND_READ_CO2);
  messageOut.sendData();
  delay(10);
  while(!messageIn.receiveData());
  uint8_t mess = messageIn.readByte();
  if(mess==COMMAND_READ_CO2_RE){
    c=messageIn.readInt();
  }
}