#include <stdio.h>
#include <stdint.h>

typedef uint8_t BYTE;
typedef uint16_t WORD;
typedef uint32_t DWORD;

BYTE data[13] = { 0x84, 0x12, 0xF7, 0x64, 0x18, 0x02, 0x05, 0x00, 0xBB, 0x32, 0xE7, 0x64, 0x08 };

WORD calc_crc16_byte(WORD crc, BYTE data)
{
    WORD temp = data;
    crc = crc ^ (temp * 256);

    DWORD bitIndex = 8;
    do
    {
        DWORD carry = (crc >= 0x8000);
        crc = (crc * 2) & 0xffff;
        
        if (carry)
        { crc = crc ^ 0x1021; }
        bitIndex = bitIndex - 1;
    }
    while (bitIndex > 0);

    return crc;
}

WORD calc_crc16(void *data, DWORD length)
{
    WORD crc = 0xFFFF;
    BYTE *bytes = (uint8_t *)data;
    for (uint32_t i = 0; i < length; i++)
    { crc = calc_crc16_byte(crc, bytes[i]); }
    return crc;
}

int main() 
{
    WORD crc = calc_crc16(data, 13);
    printf("CRC16: 0x%x\n", crc); //Should be 0xB81B
    return 0;
}