crc ssp 算法 校验 通讯
#define FALSE 0x00
#define TRUE 0x01
#define uchar unsigned char
#define uint unsigned int
uchar CrcL,CrcH;
const uint CrcTable[8*32]=
{
0x0000,0x8005,0x800F,0x000A,0x801B,0x001E,0x0014,0x8011,
0x8033,0x0036,0x003C,0x8039,0x0028,0x802D,0x8027,0x0022,
0x8063,0x0066,0x006C,0x8069,0x0078,0x807D,0x8077,0x0072,
0x0050,0x8055,0x805F,0x005A,0x804B,0x004E,0x0044,0x8041,
0x80C3,0x00C6,0x00CC,0x80C9,0x00D8,0x80DD,0x80D7,0x00D2,
0x00F0,0x80F5,0x80FF,0x00FA,0x80EB,0x00EE,0x00E4,0x80E1,
0x00A0,0x80A5,0x80AF,0x00AA,0x80BB,0x00BE,0x00B4,0x80B1,
0x8093,0x0096,0x009C,0x8099,0x0088,0x808D,0x8087,0x0082,
0x8183,0x0186,0x018C,0x8189,0x0198,0x819D,0x8197,0x0192,
0x01B0,0x81B5,0x81BF,0x01BA,0x81AB,0x01AE,0x01A4,0x81A1,
0x01E0,0x81E5,0x81EF,0x01EA,0x81FB,0x01FE,0x01F4,0x81F1,
0x81D3,0x01D6,0x01DC,0x81D9,0x01C8,0x81CD,0x81C7,0x01C2,
0x0140,0x8145,0x814F,0x014A,0x815B,0x015E,0x0154,0x8151,
0x8173,0x0176,0x017C,0x8179,0x0168,0x816D,0x8167,0x0162,
0x8123,0x0126,0x012C,0x8129,0x0138,0x813D,0x8137,0x0132,
0x0110,0x8115,0x811F,0x011A,0x810B,0x010E,0x0104,0x8101,
0x8303,0x0306,0x030C,0x8309,0x0318,0x831D,0x8317,0x0312,
0x0330,0x8335,0x833F,0x033A,0x832B,0x032E,0x0324,0x8321,
0x0360,0x8365,0x836F,0x036A,0x837B,0x037E,0x0374,0x8371,
0x8353,0x0356,0x035C,0x8359,0x0348,0x834D,0x8347,0x0342,
0x03C0,0x83C5,0x83CF,0x03CA,0x83DB,0x03DE,0x03D4,0x83D1,
0x83F3,0x03F6,0x03FC,0x83F9,0x03E8,0x83ED,0x83E7,0x03E2,
0x83A3,0x03A6,0x03AC,0x83A9,0x03B8,0x83BD,0x83B7,0x03B2,
0x0390,0x8395,0x839F,0x039A,0x838B,0x038E,0x0384,0x8381,
0x0280,0x8285,0x828F,0x028A,0x829B,0x029E,0x0294,0x8291,
0x82B3,0x02B6,0x02BC,0x82B9,0x02A8,0x82AD,0x82A7,0x02A2,
0x82E3,0x02E6,0x02EC,0x82E9,0x02F8,0x82FD,0x82F7,0x02F2,
0x02D0,0x82D5,0x82DF,0x02DA,0x82CB,0x02CE,0x02C4,0x82C1,
0x8243,0x0246,0x024C,0x8249,0x0258,0x825D,0x8257,0x0252,
0x0270,0x8275,0x827F,0x027A,0x826B,0x026E,0x0264,0x8261,
0x0220,0x8225,0x822F,0x022A,0x823B,0x023E,0x0234,0x8231,
0x8213,0x0216,0x021C,0x8219,0x0208,0x820D,0x8207,0x0202
};
//------------------------------------
void UpdateCrc(const uchar num)
{
uint table_addr;
table_addr=(num ^ Crch);
Crch=(CrcTable[table_addr] >> 8) ^ CrcL;
CrcL=(CrcTable[table_addr] & 0x00FF);
}
//------------------------------------
void ResetCrc(void)
{
CrcL=0xFF;
CrcH=0xFF;
}
应用示例: 对 7F 80 03 02 FF FF 进行校验,假设 WrBuf[] 存放的数据是 0x7f..0xff,0xff 等待数据,
该数据包的 Crc 计算如下:
int i0,s_len;
ResetCrc();
for(i0=1;i0<6;i0++) UpdateCrc(WrBuf[i0]); // 计算 Crc，0x7f 不参加 Crc 计算
WrBuf[i0++]=CrcL;
WrBuf[i0++]=CrcH;
s_len=i0;
for(i0=0;i0<s_len;i0++) SendChar (WrBuf[i0]); // 数据发送到识币器
本人对CRC算法一点也不懂，哪位给就这个例子详细讲讲，谢谢！（“UpdateCrc(WrBuf[i0])”这个数组的下标值是多少啊？） 算法 CRC?SSP
[解决办法]
建议 LZ 你将想知道的值打印出来，这样结合源代码分析
[解决办法]
CRC核心原理是一样的，你要知道百度一下就行了，讲的很详细。这里很多过程并不好输入。
另外CRC根据位数不同也有很多不同的多项式与之对应。不同的多项式最后会导致table的内容不一样。
初始值也未必一样。
