【CRC笔记】CRC-8 SMBUS C语言实现

一、CRC-8 SMBUS算法简介

别名：CRC-8

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二、CRC-8/SMBUS算法基本信息

CRC算法名称	CRC-8/SMBUS
多项式公式	x8 + x2 + x + 1
宽度width	8
多项式poly	0x07
初始值init	0x00
输入反转refin	false
输出反转refout	false
输出结果异或值xorout	0x00
check	0xF4
residue	0x00

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三、CRC-8/SMBUS算法的C语言实现

1、查表法计算CRC-8/SMBUS

/* CRC余式表 */
const unsigned char crc_table[256] = {
    0x00, 0x07, 0x0e, 0x09, 0x1c, 0x1b, 0x12, 0x15, 
    0x38, 0x3f, 0x36, 0x31, 0x24, 0x23, 0x2a, 0x2d, 
    0x70, 0x77, 0x7e, 0x79, 0x6c, 0x6b, 0x62, 0x65, 
    0x48, 0x4f, 0x46, 0x41, 0x54, 0x53, 0x5a, 0x5d, 
    0xe0, 0xe7, 0xee, 0xe9, 0xfc, 0xfb, 0xf2, 0xf5, 
    0xd8, 0xdf, 0xd6, 0xd1, 0xc4, 0xc3, 0xca, 0xcd, 
    0x90, 0x97, 0x9e, 0x99, 0x8c, 0x8b, 0x82, 0x85, 
    0xa8, 0xaf, 0xa6, 0xa1, 0xb4, 0xb3, 0xba, 0xbd, 
    0xc7, 0xc0, 0xc9, 0xce, 0xdb, 0xdc, 0xd5, 0xd2, 
    0xff, 0xf8, 0xf1, 0xf6, 0xe3, 0xe4, 0xed, 0xea, 
    0xb7, 0xb0, 0xb9, 0xbe, 0xab, 0xac, 0xa5, 0xa2, 
    0x8f, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9d, 0x9a, 
    0x27, 0x20, 0x29, 0x2e, 0x3b, 0x3c, 0x35, 0x32, 
    0x1f, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0d, 0x0a, 
    0x57, 0x50, 0x59, 0x5e, 0x4b, 0x4c, 0x45, 0x42, 
    0x6f, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7d, 0x7a, 
    0x89, 0x8e, 0x87, 0x80, 0x95, 0x92, 0x9b, 0x9c, 
    0xb1, 0xb6, 0xbf, 0xb8, 0xad, 0xaa, 0xa3, 0xa4, 
    0xf9, 0xfe, 0xf7, 0xf0, 0xe5, 0xe2, 0xeb, 0xec, 
    0xc1, 0xc6, 0xcf, 0xc8, 0xdd, 0xda, 0xd3, 0xd4, 
    0x69, 0x6e, 0x67, 0x60, 0x75, 0x72, 0x7b, 0x7c, 
    0x51, 0x56, 0x5f, 0x58, 0x4d, 0x4a, 0x43, 0x44, 
    0x19, 0x1e, 0x17, 0x10, 0x05, 0x02, 0x0b, 0x0c, 
    0x21, 0x26, 0x2f, 0x28, 0x3d, 0x3a, 0x33, 0x34, 
    0x4e, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5c, 0x5b, 
    0x76, 0x71, 0x78, 0x7f, 0x6a, 0x6d, 0x64, 0x63, 
    0x3e, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2c, 0x2b, 
    0x06, 0x01, 0x08, 0x0f, 0x1a, 0x1d, 0x14, 0x13, 
    0xae, 0xa9, 0xa0, 0xa7, 0xb2, 0xb5, 0xbc, 0xbb, 
    0x96, 0x91, 0x98, 0x9f, 0x8a, 0x8d, 0x84, 0x83, 
    0xde, 0xd9, 0xd0, 0xd7, 0xc2, 0xc5, 0xcc, 0xcb, 
    0xe6, 0xe1, 0xe8, 0xef, 0xfa, 0xfd, 0xf4, 0xf3,
};

//查表法计算crc
unsigned char do_crc_table(unsigned char *ptr,int len)
{
    unsigned char crc = 0x00;

    while(len--) 
    {
        crc = crc_table[(crc ^ *ptr++) & 0xff];
    }
    
    return crc;
}

2、直接计算法计算CRC-8/SMBUS

//直接计算法计算crc
unsigned char do_crc(unsigned char *ptr, int len)
{
    unsigned int i;
    unsigned char crc = 0x00;
    
    while(len--)
    {
        crc ^= *ptr++;
        for ( i = 0; i < 8; i++ )
        {
            if ( crc & 0x80 )
                crc = (crc << 1) ^ 0x07;
            else
                crc <<= 1;
        }
    }
    
    return crc;
}

3、测试程序

//测试数据
unsigned char test_buff[]={
    0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
    0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 
    0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
    0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 
    0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
    0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 
    0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
    0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 
    0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
    0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 
    0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
    0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 
    0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
    0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 
    0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
    0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 
    0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
    0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 
    0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
    0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 
    0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
    0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, 
    0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
    0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 
    0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
    0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 
    0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
    0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, 
    0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
    0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 
    0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
    0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff
};

int main(int argc, char* argv[])
{
    unsigned char crc;

    //查表法
    crc = do_crc_table(test_buff, sizeof(test_buff));
    printf("CRC-8/SMBUS : 0x%x\n", crc);

    //直接计算法
    crc = do_crc(test_buff, sizeof(test_buff));
    printf("CRC-8/SMBUS : 0x%x\n", crc);

    return 0;
}

测试结果

CRC-8/SMBUS : 0x14
CRC-8/SMBUS : 0x14

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[参考资料]

CRC RevEng

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