The following code snippet describes how to generate an 8-bit CRC code in C for the HDC3x devices.

#include <stdio.h>
unsigned char crcHDC3 (unsigned char msg[], int msglen) {
    unsigned char crc = 0xFF;
    for (int byte = 0; byte < msglen; byte++) {
        crc ^= msg[byte];
        for (int bit = 0; bit < 8; bit++) {
            if (crc & 0x80) 
                crc = (crc << 1) ^ 0x31;
            else 
                crc = (crc << 1);
        }
    }
    return crc;
}
void main(int argc, char *argv[]) {
    unsigned char msg[20];
    int msglen = (argc > 1) ? (argc - 1) : 2;
    msg[0] = 0xAB;
    msg[1] = 0xCD;
    for (int i = 1; i < argc; i++) {
        sscanf(argv[i], "%X", &msg[i-1]);
    }
    printf("crc" 0x%X\n", crcHDC3(msg, msglen));
}