http://www.gongkong.com/tech/detail.asp?id=154132

void CRC_check(unsigned char *buff, int len, unsigned char *chk) { unsigned short crc; unsigned char *cptr; int i; crc=0xFFFF; for(i=0; i <len; i++) { CRC_calc(buff[i] , &crc); } cptr=(unsigned char *)&crc; chk[0]=*(cptr); // Low Byte first chk[1]=*(cptr+1); // High byte return; } /*...........................................................................*/ /* CRC one byte calculation */ /*...........................................................................*/ void CRC_calc(unsigned char c, unsigned short *crc) { unsigned char bn; unsigned short i; for(i = 8 ; i > 0 ; i--) { bn = c; c /=(unsigned char) 2; if((*crc & 0x0001)){ bn++; } *crc /=(unsigned short) 2; if((bn & 0x0001)){ *crc ^= 0xa001; } } return; }