uss_crc.c

#include "uss_crc.h"

uint16 uss_crc_16(uint8 *data, uint16 len, uint16 seed)
{
    uint16 crc16 = seed;
    uint8 i;

    while (len--) {
        for (i = 0x80; i != 0; i >>= 1) {
            if ((crc16 & 0x8000) != 0) {
                crc16 = crc16 << 1;
                crc16 = crc16 ^ 0x1021;
            } else {
                crc16 = crc16 << 1;
            }
            if ((*data & i) != 0) {
                crc16 = crc16 ^ 0x1021; // crc16 = crc16 ^ (0x10000 ^ 0x11021)
            }
        }
        data++;
    }
    return crc16;
}

uint8 uss_crc_8(uint8 *data, uint16 len, uint8 seed, uint8 xor_out)
{
    uint8 crc8 = seed;
    uint8 i;

    while (len--) {
        for (i = 0x80; i != 0; i >>= 1) {
            if ((crc8 & 0x80) != 0) {
                crc8 = crc8 << 1;
                crc8 = crc8 ^ 0x2F;
            } else {
                crc8 = crc8 << 1;
            }
            if ((*data & i) != 0) {
                crc8 = crc8 ^ 0x2F;  //crc8 = crc8 ^ (0x100 ^ 0x12F)
            }
        }
        data++;
    }
    return (crc8 ^ xor_out);
}

static const uint16 crc_table[16] ={0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef};

uint16 calculated_crc16(uint16 *data, uint16 word_count) {
    uint16 crc16 = 0xFFFF;//E521_42_CRC16_CALCULATE_SEED;
    uint16 crc_h4, crc_l12;
  
    while( word_count-- ) {
        crc_h4 = (crc16 >> 12);
        crc_l12 = (crc16 << 4);
        crc16 = crc_l12 ^ crc_table[crc_h4 ^ (*data >> 12)];

        crc_h4 = (crc16 >> 12);
        crc_l12 = (crc16 << 4);
        crc16 = crc_l12 ^ crc_table[crc_h4 ^ ((*data >> 8) & 0x0f)];

        crc_h4 = (crc16 >> 12);
        crc_l12 = (crc16 << 4);
        crc16 = crc_l12 ^ crc_table[crc_h4 ^ ((*data & 0x00ff) >> 4)];

        crc_h4 = (crc16 >> 12);
        crc_l12 = (crc16 << 4);
        crc16 = crc_l12 ^ crc_table[crc_h4 ^ (*data & 0x000f)];

        data++;
    }

    return crc16; 
}