Fletcher Checksum

The checksum is a 2 byte Fletcher checksum and encompasses all the bytes in the packet (excluding the packet checksum bytes)

Fletcher Checksum algorithm

uint16_t fletcher_checksum(const uint8_t* packet, int packet_length)

{

  // Checksum covers from the first header byte to the last payload byte.

  // This should be equal to the payload length plus the 4 header bytes.

  const int checksum_length = packet_length - 2;

  uint8_t checksum_MSB = 0;

  uint8_t checksum_LSB = 0;

  // Iterate over the packet to compute the checksum.

  for(int i=0; i<checksum_length; i++)

  {

    checksum_MSB += packet[i];

    checksum_LSB += checksum_MSB;

  }

  return ((uint16_t)checksum_MSB << 8) | (uint16_t)checksum_LSB;

}