WiRC CRC table

gistfile1.js

// example body

var buf = new Buffer(9);

// start of frame
buf[0] = '0xAA';
buf[1] = '0xBB';

// message to send - crc is based on this
var msg = ['0x01', '0x03', '0x00', '0x00', '0x01'];

// expected crc result
var crc = ['0x21','0xAC'];

gistfile2.c

** Internal function to calculate CRC for a message 
 *
 *  @param  p_sp_msg    the message the CRC shall be calculated for
 *  @return the calculated CRC16 value
 *
 *  The function calculates CRC-CCITT from the following fields of the message:
 *      - command code
 *      - length
 *      - message body
 */
static uint16_t l_calc_msg_crc_f(const msg_s_message_t* p_sp_msg) 
{
    uint16_t u16_crc = 0u;
    uint8_t u8_index;
    uint8_t u8_length;

    /* add command code to CRC */
    u16_crc = l_crc_ccitt_f(u16_crc, p_sp_msg->u8_cmd);
    /* add length to CRC */
    u16_crc = l_crc_ccitt_f(u16_crc, p_sp_msg->u8_len);
    /* add message body to the calculation */
    for(u8_index = 0u, u8_length = p_sp_msg->u8_len; 
        u8_index < u8_length; ++u8_index) {
        u16_crc = l_crc_ccitt_f(u16_crc, p_sp_msg->au8_body[u8_index]);
    }

    return u16_crc;
}

/** Internal function to calculate CRC-CCIT value
 *
 *  @param  p_u16_init  initial value of the CRC calculator
 *  @param  p_u8_byte   new byte shall be added to the CRC calculation
 *  @return calculated CRC value
 *
 *  The function implements CRC-CCITT calculation:
 *  The CRC polynomial: X^16 + X^12 + X^5 + 1
 */
static inline uint16_t l_crc_ccitt_f(uint16_t p_u16_init, uint8_t p_u8_byte)
{
    static const uint16_t l_au16_ccitt_crc16_table_c[256] = {
        0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
        0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
        0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
        0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
        0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
        0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
        0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
        0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
        0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823,
        0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
        0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12,
        0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
        0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41,
        0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
        0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70,
        0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
        0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
        0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
        0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
        0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
        0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
        0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
        0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
        0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
        0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
        0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3,
        0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
        0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92,
        0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
        0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1,
        0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
        0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0
    };
    uint16_t u16_crc;
    uint8_t u8_idx;
    
    u8_idx = (p_u16_init >> 8) ^ p_u8_byte;
    u16_crc = l_au16_ccitt_crc16_table_c[u8_idx] ^ (p_u16_init << 8);

    return u16_crc;
}