赞
踩
CRC16常见的标准有以下几种,被用在各个规范中,其算法原理基本一致,就是在数据的输入和输出有所差异,下边把这些标准的差异列出,并给出C语言的算法实现。
CRC16_CCITT:多项式x16+x12+x5+1(0x1021),初始值0x0000,低位在前,高位在后,结果与0x0000异或
CRC16_CCITT_FALSE:多项式x16+x12+x5+1(0x1021),初始值0xFFFF,低位在后,高位在前,结果与0x0000异或
CRC16_XMODEM:多项式x16+x12+x5+1(0x1021),初始值0x0000,低位在后,高位在前,结果与0x0000异或
CRC16_X25:多项式x16+x12+x5+1(0x1021),初始值0x0000,低位在前,高位在后,结果与0xFFFF异或
CRC16_MODBUS:多项式x16+x15+x2+1(0x8005),初始值0xFFFF,低位在前,高位在后,结果与0x0000异或
CRC16_IBM:多项式x16+x15+x2+1(0x8005),初始值0x0000,低位在前,高位在后,结果与0x0000异或
CRC16_MAXIM:多项式x16+x15+x2+1(0x8005),初始值0x0000,低位在前,高位在后,结果与0xFFFF异或
CRC16_USB:多项式x16+x15+x2+1(0x8005),初始值0xFFFF,低位在前,高位在后,结果与0xFFFF异或
模式 | 多项式 | 初始值 | 数据位序 | 结果处理 |
CRC16_CCITT | x16+x12+x5+1(0x1021) | 0x0000 | 低位在前,高位在后 | 与0x0000异或 |
CRC16_CCITT_FALSE | x16+x12+x5+1(0x1021) | 0xFFFF | 低位在后,高位在前 | 与0x0000异或 |
CRC16_XMODEM | x16+x12+x5+1(0x1021) | 0x0000 | 低位在后,高位在前 | 与0x0000异或 |
CRC16_X25 | x16+x12+x5+1(0x1021) | 0x0000 | 低位在后,高位在前 | 与0xFFFF异或 |
CRC16_ MODBUS | x16+x15+x2+1(0x8005) | 0xFFFF | 低位在前,高位在后 | 与0x0000异或 |
CRC16_ IBM | x16+x15+x2+1(0x8005) | 0x0000 | 低位在前,高位在后 | 与0x0000异或 |
CRC16_ MAXIM | x16+x15+x2+1(0x8005) | 0x0000 | 低位在前,高位在后 | 与0xFFFF异或 |
CRC16_ USB | x16+x15+x2+1(0x8005) | 0xFFFF | 低位在前,高位在后 | 与0xFFFF异或 |
多项式产生:
如x16+x12+x5+1
x16表示第16位为1,x5表示第5位为1
(1 << 16) | (1 << 12) | (1 << 5) | (1) = 0x11021
但是CRC16只取低16位,写成16进制数就是 0x1021
CRC16的算法原理:
1.根据CRC16的标准选择初值CRCIn的值。
2.将数据的第一个字节与CRCIn高8位异或。
3.判断最高位,若该位为 0 左移一位,若为 1 左移一位再与多项式Hex码异或。
4.重复3直至8位全部移位计算结束。
5.重复将所有输入数据操作完成以上步骤,所得16位数即16位CRC校验码。根据算法原理与标准要求就能简单的写出具体程序:
-
unsigned short CRC16_CCITT(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar,&wChar);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin) ;
-
}
-
unsigned short CRC16_CCITT_FALSE(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
return (wCRCin) ;
-
}
-
unsigned short CRC16_XMODEM(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
return (wCRCin) ;
-
}
-
-
unsigned short CRC16_X25(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar,&wChar);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin^
0xFFFF) ;
-
}
-
-
unsigned short CRC16_MODBUS(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar,&wChar);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin) ;
-
}
-
unsigned short CRC16_IBM(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar,&wChar);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin) ;
-
}
-
unsigned short CRC16_MAXIM(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar,&wChar);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin^
0xFFFF) ;
-
}
-
unsigned short CRC16_USB(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar,&wChar);
-
wCRCin ^= (wChar <<
8);
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
else
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin^
0xFFFF) ;
-
}
-
void InvertUint8(unsigned char *dBuf,unsigned char *srcBuf)
-
{
-
int i;
-
unsigned
char tmp[
4];
-
tmp[
0] =
0;
-
for(i=
0;i<
8;i++)
-
{
-
if(srcBuf[
0]& (
1 << i))
-
tmp[
0]|=
1<<(
7-i);
-
}
-
dBuf[
0] = tmp[
0];
-
-
}
-
void InvertUint16(unsigned short *dBuf,unsigned short *srcBuf)
-
{
-
int i;
-
unsigned
short tmp[
4];
-
tmp[
0] =
0;
-
for(i=
0;i<
16;i++)
-
{
-
if(srcBuf[
0]& (
1 << i))
-
tmp[
0]|=
1<<(
15 - i);
-
}
-
dBuf[
0] = tmp[
0];
-
}
-
void InvertUint32(unsigned int *dBuf,unsigned int *srcBuf)
-
{
-
int i;
-
unsigned
int tmp[
4];
-
-
tmp[
0] =
0;
-
-
for(i=
0;i<
32;i++)
-
{
-
if(srcBuf[
0]& (
1 << i))
-
tmp[
0]|=
1<<(
15 - i);
-
}
-
dBuf[
0] = tmp[
0];
-
}
-
具体验证使用这个工具,内含CRC算法的计算,和后边的博客中提到的其他算法的工具合集
在这个基础上也加入CRC32 的校验算法
-
//CRC32算法:
-
unsigned int CRC32(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
int i;
-
unsigned int wCRCin = 0xFFFFFFFF;
-
unsigned int wCPoly = 0x04C11DB7;
-
unsigned int wChar = 0;
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8((unsigned char *)&wChar,(unsigned char *)&wChar);
-
wCRCin ^= (wChar
<< 24);
-
for(i = 0;i < 8;i++)
-
{
-
if(wCRCin & 0x80000000)
-
wCRCin = (wCRCin << 1) ^ wCPoly;
-
else
-
wCRCin = wCRCin << 1;
-
}
-
}
-
InvertUint32(&wCRCin,&wCRCin);
-
return (wCRCin ^ 0xFFFFFFFF) ;
-
}
-
现选择最常用的CRC-16校验,说明它的使用方法。
根据Modbus协议,常规485通讯的信息发送形式如下:
地址 功能码 数据信息 校验码
1byte 1byte nbyte 2byte
CRC校验是前面几段数据内容的校验值,为一个16位数据,发送时,低8位在前,高8为最后。
例如:信息字段代码为: 1011001,校验字段为:1010。
发送方:发出的传输字段为: 1 0 1 1 0 0 1 1 0 10
信息字段 校验字段
接收方:使用相同的计算方法计算出信息字段的校验码,对比接收到的实际校验码,如果相等及信息正确,不相等则信息错误;或者将接受到的所有信息除多项式,如果能够除尽,则信息正确。
常用查表法和计算法。计算方法一般都是:
(1)、预置1个16位的寄存器值0xFFFF,称此寄存器为CRC寄存器;
(2)、把第一个8位二进制数据(既通讯信息帧的第一个字节)与16位的CRC寄存器的低
8位相异或,把结果放于CRC寄存器,高八位数据不变;
(3)、把CRC寄存器的内容右移一位(朝高位)用0填补最高位,并检查右移后的移出位;
(4)、如果移出位为0:重复第3步(再次右移一位);如果移出位为1,CRC寄存器与一多
项式(A001)进行异或;
(5)、重复步骤3和4,直到右移8次,这样整个8位数据全部进行了处理;
(6)、重复步骤2到步骤5,进行通讯信息帧下一个字节的处理;
(7)、将该通讯信息帧所有字节按上述步骤计算完成后,得到的16位CRC寄存器的高、低
字节进行交换;
(8)、最后得到的CRC寄存器内容即为:CRC码。
以上计算步骤中的多项式A001是8005按位颠倒后的结果。
查表法是将移位异或的计算结果做成了一个表,就是将0~256放入一个长度为16位的寄存器中的低八位,高八位填充0,然后将该寄存器与多项式0XA001按照上述3、4步骤,直到八位全部移出,最后寄存器中的值就是表格中的数据,高八位、低八位分别单独一个表。
CRC16常见的标准有以下几种,被用在各个规范中,其算法原理基本一致,就是在数据的输入和输出有所差异,下边把这些标准的差异列出,并给出C语言的算法实现。
CRC16_CCITT:多项式x16+x12+x5+1(0x1021),初始值0x0000,低位在前,高位在后,结果与0x0000异或
CRC16_CCITT_FALSE:多项式x16+x12+x5+1(0x1021),初始值0xFFFF,低位在后,高位在前,结果与0x0000异或
CRC16_XMODEM:多项式x16+x12+x5+1(0x1021),初始值0x0000,低位在后,高位在前,结果与0x0000异或
CRC16_X25:多项式x16+x12+x5+1(0x1021),初始值0x0000,低位在前,高位在后,结果与0xFFFF异或
CRC16_MODBUS:多项式x16+x15+x5+1(0x8005),初始值0xFFFF,低位在前,高位在后,结果与0x0000异或
CRC16_IBM:多项式x16+x15+x5+1(0x8005),初始值0x0000,低位在前,高位在后,结果与0x0000异或
CRC16_MAXIM:多项式x16+x15+x5+1(0x8005),初始值0x0000,低位在前,高位在后,结果与0xFFFF异或
CRC16_USB:多项式x16+x15+x5+1(0x8005),初始值0xFFFF,低位在前,高位在后,结果与0xFFFF异或
1.根据CRC16的标准选择初值CRCIn的值。
2.将数据的第一个字节与CRCIn高8位异或。
3.判断最高位,若该位为 0 左移一位,若为 1 左移一位再与多项式Hex码异或。
4.重复3直至8位全部移位计算结束。
5.重复将所有输入数据操作完成以上步骤,所得16位数即16位CRC校验码。
根据算法原理与标准要求就能简单的写出具体程序:
-
/**
-
**************************************************************************************************
-
* @Brief Single byte data inversion
-
* @Param
-
* @DesBuf: destination buffer
-
* @SrcBuf: source buffer
-
* @RetVal None
-
* @Note (MSB)0101_0101 ---> 1010_1010(LSB)
-
**************************************************************************************************
-
*/
-
void InvertUint8(unsigned char *DesBuf, unsigned char *SrcBuf)
-
{
-
int i;
-
unsigned
char temp =
0;
-
-
for(i =
0; i <
8; i++)
-
{
-
if(SrcBuf[
0] & (
1 << i))
-
{
-
temp |=
1<<(
7-i);
-
}
-
}
-
DesBuf[
0] = temp;
-
}
-
-
/**
-
**************************************************************************************************
-
* @Brief double byte data inversion
-
* @Param
-
* @DesBuf: destination buffer
-
* @SrcBuf: source buffer
-
* @RetVal None
-
* @Note (MSB)0101_0101_1010_1010 ---> 0101_0101_1010_1010(LSB)
-
**************************************************************************************************
-
*/
-
void InvertUint16(unsigned short *DesBuf, unsigned short *SrcBuf)
-
{
-
int i;
-
unsigned
short temp =
0;
-
-
for(i =
0; i <
16; i++)
-
{
-
if(SrcBuf[
0] & (
1 << i))
-
{
-
temp |=
1<<(
15 - i);
-
}
-
}
-
DesBuf[
0] = temp;
-
}
-
-
unsigned short CRC16_CCITT(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar, &wChar);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
InvertUint16(&wCRCin, &wCRCin);
-
return (wCRCin) ;
-
}
-
-
unsigned short CRC16_CCITT_FALSE(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
return (wCRCin) ;
-
}
-
-
unsigned short CRC16_XMODEM(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
return (wCRCin) ;
-
}
-
-
unsigned short CRC16_X25(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x1021;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar, &wChar);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0;i <
8;i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
InvertUint16(&wCRCin, &wCRCin);
-
return (wCRCin^
0xFFFF) ;
-
}
-
-
unsigned short CRC16_MODBUS(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar, &wChar);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
InvertUint16(&wCRCin, &wCRCin);
-
return (wCRCin) ;
-
}
-
-
unsigned short CRC16_IBM(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar, &wChar);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
InvertUint16(&wCRCin,&wCRCin);
-
return (wCRCin) ;
-
}
-
-
unsigned short CRC16_MAXIM(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0x0000;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar, &wChar);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
InvertUint16(&wCRCin, &wCRCin);
-
return (wCRCin^
0xFFFF) ;
-
}
-
-
unsigned short CRC16_USB(unsigned char *puchMsg, unsigned int usDataLen)
-
{
-
unsigned
short wCRCin =
0xFFFF;
-
unsigned
short wCPoly =
0x8005;
-
unsigned
char wChar =
0;
-
-
while (usDataLen--)
-
{
-
wChar = *(puchMsg++);
-
InvertUint8(&wChar, &wChar);
-
wCRCin ^= (wChar <<
8);
-
-
for(
int i =
0; i <
8; i++)
-
{
-
if(wCRCin &
0x8000)
-
{
-
wCRCin = (wCRCin <<
1) ^ wCPoly;
-
}
-
else
-
{
-
wCRCin = wCRCin <<
1;
-
}
-
}
-
}
-
InvertUint16(&wCRCin, &wCRCin);
-
return (wCRCin^
0xFFFF) ;
-
}
Copyright © 2003-2013 www.wpsshop.cn 版权所有,并保留所有权利。