bool CRC_Check(void)
{
  unsigned short sum = 0;
  sum = slow_crc16(sum, (unsigned char __flash *)0, (unsigned long)&__checksum);
  sum = slow_crc16(sum, (unsigned char __flash *)&zero, sizeof(zero));
  if(sum != __checksum) return(0); //return if test fail
  return(1); //test passed
}

//Calculate CRC16:

unsigned short slow_crc16(unsigned short sum,
                          unsigned char __flash *p,
                          unsigned long len)
{
  while(len--)
  {
    int i;
    unsigned char byte = *p++;
    for(i = 0; i < 8; ++i)
    {
      unsigned long osum = sum;
      sum <<= 1;
      if(byte & 0x80)
        sum |= 1;
      if(osum & 0x8000)
        sum ^= 0x1021;
      byte <<=1;
    }
  }
  return sum;
}