CRC16 循環冗餘校驗

循環冗餘校驗再單片機的通訊數據傳輸環節用得比較多，目的是方式電訊號干擾導致得誤傳。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define u8  unsigned char
#define u16 unsigned short
#define u32 unsigned int 

void CalclationCRC16(u8 *dat, u8 datLen, u8* crc16)
{
	u8 i = 0;
	u16 r = 0x0000;	//存儲CRC 結果
	u16 p = 0x1021;	//CRC因子
	u8  t = 0;
	while (datLen--)
	{
		t = *(dat++);
		r ^= t << 8;
		for (i = 0; i < 8; i++)
		{
			if (r & 0x8000)
			{
				r <<= 1;
				r ^= p;
			}
			else
			{
				r <<= 1;
			}
		}

	}
	crc16[1] = r >> 8;
	crc16[0] = r % 256;
}

void CRC_CCITT_FALSE(u8 *dat, u8 datLen, u8* crc16)
{
	u8 i = 0;
	u16 r = 0xFFFF;	//存儲CRC 結果
	u16 p = 0x1021;	//CRC因子
	u8  t = 0;
	while (datLen--)
	{
		t = *(dat++);
		r ^= t << 8;
		for (i = 0; i < 8; i++)
		{
			if (r & 0x8000)
			{
				r <<= 1;
				r ^= p;
			}
			else
			{
				r <<= 1;
			}
		}

	}
	crc16[1] = r >> 8;
	crc16[0] = r % 256;
}



u32 crc_chk(u8 *crcbuf, u8 n)
{
	u8 i, j, tt;
	u32 CRCX = 0xffff;
	for (i = 0; i < n; i++)
	{
		CRCX = CRCX ^ crcbuf[i];
		for (j = 0; j < 8; j++)
		{
			tt = CRCX & 1;
			CRCX = CRCX >> 1;
			CRCX = CRCX & 0X7fff;
			if (tt == 1)
				CRCX = CRCX ^ 0xa001;
			CRCX = CRCX & 0xffff;
		}
	}
	return CRCX;
}


int main()
{
	u8 dat[7] = { 0x12,0x47,0x09,0x23,0x01,0x09,0x13 };
	u8 dat2[11] = { 0x00 ,0x00 ,0x07 ,0xF5 ,0x12,0x47,0x09,0x23,0x01,0x09,0x13 };
	u8 r[2];
	u32 r1;

	CalclationCRC16(dat, 7, r);
	printf("%02X%02X\n", r[1], r[0]);

	CalclationCRC16(dat2, 11, r);
	printf("%02X%02X\n", r[1], r[0]);

	return 0;
}