#include <util/crc16.h>

This header file provides a optimized inline functions for calculating cyclic redundancy checks (CRC) using common polynomials.

References:

See the Dallas Semiconductor app note 27 for 8051 assembler example and general CRC optimization suggestions. The table on the last page of the app note is the key to understanding these implementations.

Jack Crenshaw's "Implementing CRCs" article in the January 1992 isue of Embedded Systems Programming. This may be difficult to find, but it explains CRC's in very clear and concise terms. Well worth the effort to obtain a copy.

A typical application would look like:

// Dallas iButton test vector.
uint8_t serno[] = { 0x02, 0x1c, 0xb8, 0x01, 0, 0, 0, 0xa2 };

int
checkcrc(void)
{
    uint8_t crc = 0, i;

    for (i = 0; i < sizeof serno / sizeof serno[0]; i++)
        crc = _crc_ibutton_update(crc, serno[i]);

    return crc; // must be 0
}