// CRC.cpp : Defines the entry point for the console application.
//

#include "stdafx.h" 
#include "math.h"

void main()
// int check_sum(unsigned char *buff, char start, char bytes)
{
char byte_cnt,bit_cnt; /* loop counters */
unsigned int crc_reg; /* Result register */
unsigned int CRCHi, CRCLo;/*Low and high order bytes of the crc*/
crc_reg = 0xFFFF; /* Set the CRC register to all 1’s */
/* Repeat for each byte of sub string */
for(byte_cnt=start; byte_cnt<(bytes+start); byte_cnt++)
{
crc_reg = crc_reg ^ (unsigned int)buff[byte_cnt]; /*EXOR CRC & Next Byte*/
/* Test each bit of the CRC */
for(bit_cnt=0; bit_cnt<8; bit_cnt++)
{
if(crc_reg & 0x0001)
{
crc_reg = crc_reg >>1; /* IF LSB=1 EXOR CRC with A001H*/
crc_reg = crc_reg ^ 0Xa001; /* Then shift CRC toward LSB */
}
else crc_reg = crc_reg>>1; /* ELSE Shift CRC towards LSB */
}
}
CRCLo=crc_reg>>8; /*Swap the low and high order bytes of the crc result*/
CRCHi=crc_reg<<8;
crc_reg = CRCLo+CRCHi;
// return crc_reg; /*Final CRC register Result */
}