PNI CompassPoint Prime - Manual (Page 57)

Prime User Manual r08 Page 51
// Update the CRC for transmitted and received data using
// the CCITT 16bit algorithm (X^16 + X^12 + X^5 + 1).
UInt16 crc = 0;
while(len--)
{
crc = (unsigned char)(crc >> 8) | (crc << 8);
crc ^= dataPtr[index++];
crc ^= (unsigned char)(crc & 0xff) >> 4;
crc ^= (crc << 8) << 4;
crc ^= ((crc & 0xff) << 4) << 1;
}
return crc;
}