LIN

/* Create the Lin ID parity */
#define BIT(data,shift) ((addr & (1 << shift)) >> shift)
uint8_t Lin_addrParity(uint8_t addr)
{
  uint8_t p0 = BIT(addr, 0) ^ BIT(addr, 1) ^ BIT(addr, 2) ^ BIT(addr, 4);
  uint8_t p1 = ~(BIT(addr, 1) ^ BIT(addr, 3) ^ BIT(addr, 4) ^ BIT(addr, 5));
  return (p0 | (p1 << 1)) << 6;
}

/* Lin defines its checksum as an inverted 8 bit sum with carry */
uint8_t Lin_dataChecksum(const uint8_t* message, char nBytes, uint16_t sum)
{
    while (nBytes-- > 0) sum += *(message++);

    // Add the carry
    while(sum >> 8)  // In case adding the carry causes another carry
      sum = (sum & 255) + (sum >> 8);

    return (~sum);
}

/* Send a message across the Lin bus */
void Lin_send_master(uint8_t addr, const uint8_t* message, uint8_t nBytes,uint8_t proto)
{
  uint8_t addrbyte = (addr & 0x3f) | addrParity(addr);
  uint8_t cksum = dataChecksum(message, nBytes, addrbyte);
  serialBreak();       // Generate the low signal that exceeds 1 char.
  write(0x55);  // Sync byte
  write(addrbyte);  // ID byte
  write(message, nBytes);  // data bytes
  write(cksum);  // checksum
}