// same as addI2CHead
inline void addI2CHeadRC(tByteArray &data) {
  data.arr[0] = 16;    // Total msg length
  data.arr[1] = 0x02;  // I2C device address
  data.arr[2] = 0x42;  // Internal register
}

// uses mode 0x01 instead of 0x02 (PF Mode)
inline void addI2CTailRC(tByteArray &data) {
  data.arr[BUF_HEADSIZE + BUF_DATASIZE] = 11;         // Total IR command length
  data.arr[BUF_HEADSIZE + BUF_DATASIZE + 1] = 0x01;   // IRLink mode 0x01 is RC Train
  data.arr[BUF_HEADSIZE + BUF_DATASIZE + 2] = 0x01;   // Start transmitting
}


void IRTrain(tSensors link, int &toggle, int channel, int output) {
  tByteArray _iBuffer;
  tByteArray _oBuffer;

  // Clear the input buffer before we start filling it
  memset(_iBuffer, 0, sizeof(tByteArray));
  memset(_oBuffer, 0, sizeof(tByteArray));

  // This is the unencoded command for the IR receiver
  _iBuffer.arr[0] = channel << 4 + output;
  _iBuffer.arr[1] = toggle << 4 +
                    (0xF ^ channel ^ output ^ toggle);

  // update the toggle bit
  toggle = (toggle) ? 0 : 1;

  // Setup the header of the I2C packet
  addI2CHeadRC(_oBuffer);

  // Generate the data payload
  encodeBuffer(_iBuffer, _oBuffer);                       // Encode PF command

  // Setup the tail end of the packet
  addI2CTailRC(_oBuffer);
  //_oBuffer[3] = 0x80;

  transmitIR(link, _oBuffer, channel, 4);
}