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我有一个遥测流,它通过硬件 CRC 生成器传递,将 CRC 附加到每个遥测帧的末尾。现在我正在尝试做一些事情来验证硬件生成的 CRC。我有计算正确 CRC(多次验证)的旧旧代码(见下文)。但是它很慢,因为每个遥测帧都是 300+ 字节,并且可以处理超过 10,000,000+ 帧。

经过一些研究,我发现一些文献指向我使用表格驱动的方法。传统方法使用 0x8005 的 Poly,在处理之前反转每个字节的位顺序,并将 CRC 初始化为零。但是,在为具有反向和非反向输入的 poly 构建表并尝试处理数据的第一个字节 (0x10) 之后,我无法获得与旧方法生成的内容相匹配的任何内容。

在 calcCRC16 函数(如下)内部,现有方法检查其他人似乎检查 MSB 的 LSB ......并且位移在右边,而我看到的其他示例在左边。我迷失了为什么这是特别是因为在将它传递给这个函数之前交换了位顺序。我尝试过在线计算器并手动在表格中进行查找,将多边形从 8005 切换到 A001(反转)、正常和反转输入字节,以及我能想到但无法获得任何表格方法匹配的每种组合我知道对我们的硬件实现正确的遗留代码。

如果我遗漏了一些明显的东西,谁能帮助我?您将如何创建基于表的方法来创建相同的输出?我是 C++ 的新手,不太熟悉 CRC 生成,可能会忽略一些基本的东西。根据硬件 CRC 验证的示例代码和输出如下:

示例代码:我只是硬编码了已知遥测流中的几个字节作为示例

/** ********************************************************************************
* TEST CRC METHOD
*******************************************************************************/
#include <iostream>

using namespace std;

unsigned char swapBits(unsigned char d);
void calcCRC16(unsigned int *CRCVal, unsigned char value);

/** **************************************************************************
*   @function   main
*   TEST CRC METHOd
*******************************************************************************/
int main(int argc, char* argv[])
{
    short          dataLength = 5;
    unsigned int   givenCrc;
    unsigned int   calcCrc;    
    unsigned char byte[] = {0x10,0xbb,0x42,0x4d,0xfd};

    /* Init CRC. */
    calcCrc = 0;
    cout << "Inital CRC = " << hex << calcCrc << "\n";
    /* Read frame data. */
    for (int i = 0; i < dataLength; i++)
    {
        cout << "byte    = " << hex << static_cast<int16_t>(byte[i]) << " ";
        calcCRC16(&calcCrc, swapBits(byte[i]));
        cout << "calcCRC = " << hex << calcCrc << "\n";
     }
}

/** ********************************************************************
*   @function   swapBits
*   Swaps the bits so they match the order sent to CRC Gen Hardware
************************************************************************/
unsigned char swapBits(unsigned char d)
{
    unsigned char t = 0;
    int i           = 0;
    int n           = 0x80;

    for(i=0x01; i<0x100; i=i<<1)
    {
        if (d & i)
        {
            t|=n;
        }
        n=n>>1;
    }
    return t;
}

/** ********************************************************************
*   @function   calcCRC16
*   WORKING METHOD VERIFIED AGAINST CRC HARDWARE
************************************************************************/
void calcCRC16(unsigned int *CRCVal, unsigned char value)
{
    unsigned char lsb;
    unsigned char bcnt;

    for (bcnt=0 ; bcnt<8 ; bcnt++)
    {
        lsb = (value ^ *CRCVal) & 0x01;
        *CRCVal >>= 1;
        value >>= 1;
        if (lsb != 0)
        {
            *CRCVal ^= 0x8005;
        }
    }
}

输出:
初始CRC = 0
byte = 10 calcCRC = b804
byte = bb calcCRC = 1fb8
byte = 42 calcCRC = 461d
byte = 4d calcCRC = 3d47
byte = fd calcCRC = 683e

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1 回答 1

3

rev16(crc16(0, buf, len))会给你列出的CRC。

#include <stdio.h>

static unsigned short crc16_table[] = {
    0x0000, 0xa001, 0xe003, 0x4002, 0x6007, 0xc006, 0x8004, 0x2005,
    0xc00e, 0x600f, 0x200d, 0x800c, 0xa009, 0x0008, 0x400a, 0xe00b,
    0x201d, 0x801c, 0xc01e, 0x601f, 0x401a, 0xe01b, 0xa019, 0x0018,
    0xe013, 0x4012, 0x0010, 0xa011, 0x8014, 0x2015, 0x6017, 0xc016,
    0x403a, 0xe03b, 0xa039, 0x0038, 0x203d, 0x803c, 0xc03e, 0x603f,
    0x8034, 0x2035, 0x6037, 0xc036, 0xe033, 0x4032, 0x0030, 0xa031,
    0x6027, 0xc026, 0x8024, 0x2025, 0x0020, 0xa021, 0xe023, 0x4022,
    0xa029, 0x0028, 0x402a, 0xe02b, 0xc02e, 0x602f, 0x202d, 0x802c,
    0x8074, 0x2075, 0x6077, 0xc076, 0xe073, 0x4072, 0x0070, 0xa071,
    0x407a, 0xe07b, 0xa079, 0x0078, 0x207d, 0x807c, 0xc07e, 0x607f,
    0xa069, 0x0068, 0x406a, 0xe06b, 0xc06e, 0x606f, 0x206d, 0x806c,
    0x6067, 0xc066, 0x8064, 0x2065, 0x0060, 0xa061, 0xe063, 0x4062,
    0xc04e, 0x604f, 0x204d, 0x804c, 0xa049, 0x0048, 0x404a, 0xe04b,
    0x0040, 0xa041, 0xe043, 0x4042, 0x6047, 0xc046, 0x8044, 0x2045,
    0xe053, 0x4052, 0x0050, 0xa051, 0x8054, 0x2055, 0x6057, 0xc056,
    0x205d, 0x805c, 0xc05e, 0x605f, 0x405a, 0xe05b, 0xa059, 0x0058,
    0xa0e9, 0x00e8, 0x40ea, 0xe0eb, 0xc0ee, 0x60ef, 0x20ed, 0x80ec,
    0x60e7, 0xc0e6, 0x80e4, 0x20e5, 0x00e0, 0xa0e1, 0xe0e3, 0x40e2,
    0x80f4, 0x20f5, 0x60f7, 0xc0f6, 0xe0f3, 0x40f2, 0x00f0, 0xa0f1,
    0x40fa, 0xe0fb, 0xa0f9, 0x00f8, 0x20fd, 0x80fc, 0xc0fe, 0x60ff,
    0xe0d3, 0x40d2, 0x00d0, 0xa0d1, 0x80d4, 0x20d5, 0x60d7, 0xc0d6,
    0x20dd, 0x80dc, 0xc0de, 0x60df, 0x40da, 0xe0db, 0xa0d9, 0x00d8,
    0xc0ce, 0x60cf, 0x20cd, 0x80cc, 0xa0c9, 0x00c8, 0x40ca, 0xe0cb,
    0x00c0, 0xa0c1, 0xe0c3, 0x40c2, 0x60c7, 0xc0c6, 0x80c4, 0x20c5,
    0x209d, 0x809c, 0xc09e, 0x609f, 0x409a, 0xe09b, 0xa099, 0x0098,
    0xe093, 0x4092, 0x0090, 0xa091, 0x8094, 0x2095, 0x6097, 0xc096,
    0x0080, 0xa081, 0xe083, 0x4082, 0x6087, 0xc086, 0x8084, 0x2085,
    0xc08e, 0x608f, 0x208d, 0x808c, 0xa089, 0x0088, 0x408a, 0xe08b,
    0x60a7, 0xc0a6, 0x80a4, 0x20a5, 0x00a0, 0xa0a1, 0xe0a3, 0x40a2,
    0xa0a9, 0x00a8, 0x40aa, 0xe0ab, 0xc0ae, 0x60af, 0x20ad, 0x80ac,
    0x40ba, 0xe0bb, 0xa0b9, 0x00b8, 0x20bd, 0x80bc, 0xc0be, 0x60bf,
    0x80b4, 0x20b5, 0x60b7, 0xc0b6, 0xe0b3, 0x40b2, 0x00b0, 0xa0b1};

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

unsigned crc16(unsigned crc, unsigned char *buf, int len)
{
    while (len--) {
        crc ^= *buf++ << 8;
        crc = (crc << 8) ^ crc16_table[(crc >> 8) & 0xff];
    }
    return crc & 0xffff;
}

inline unsigned rev16(unsigned val)
{
    return (rev_table[val & 0xff] << 8) | rev_table[(val >> 8) & 0xff];
}
于 2013-04-27T01:51:15.273 回答