18b20 crc问题
最近在做18b20的试验,现在温度是正常显示了。但感觉温度显示和别人做的相比稍微有点差异。我的显示31.0,别人的显示29.6.(同样的环境,封装)。搞不懂为什么误差这么大,现在想加个CRC校验,网上找的资料比较少,请问谁能讲解一下或者给些详细资料,谢谢了. 顶起来别沉啊.. 有CRC吗,误差不大呀 5612404 发表于 2012-9-5 20:26 static/image/common/back.gif有CRC吗,误差不大呀
没有,现在想添加crc校验到程序里面,单片机是M128,编译器是ICCAVR CRC种类有好多类型。CRC8,CRC16,CRC32,计算方式也不一样。关键看你的多项式。 正常,规格正负0.5度偏差,稍微超一些也还好吧。 本帖最后由 coleyao 于 2012-9-6 15:04 编辑
const uchar CrcTable=
{0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53};
//-------------CRC Check----------------------
uchar CRC_OK(uchar *p)
{
uchar OutData,InData;
uchar countbyte,bitlen;
uchar crctem1,crctem2;
OutData=0;
for(countbyte=1;countbyte<10;countbyte++)
{
InData=*p;
for(bitlen=1;bitlen<9;bitlen++)
{
crctem1=OutData;
crctem2=crctem1^InData;
crctem2&=0x01;
OutData>>=1;
if(crctem2)
{
OutData+=0x80;
OutData^=0x0c;
}
InData>>=1;
}
p++;
}
return(!OutData);
}
uchar CRC_OK1(uchar *p1,uchar num)
{
uchar OutData1;
uchar countbyte1;
OutData1=0;
for(countbyte1=1;countbyte1<num;countbyte1++)
{
OutData1=CrcTable;
p1++;
}
p1-=(num-1);
return(OutData1);
}
//-------------CRC Check----------------------
Buf18B20A=Read_18B20(); //== 读低位 =====
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
Buf18B20A=Read_18B20();
if((Buf18B20A!=0xff)||!CRC_OK(Buf18B20A))。。。。//如果校验错。。。。 coleyao 发表于 2012-9-6 14:52 static/image/common/back.gif
const uchar CrcTable=
{0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65, ...
首先感谢你的程序,还没看懂。能讲解下原理吗?{:3_59:} tianluo 发表于 2012-9-6 19:21 static/image/common/back.gif
首先感谢你的程序,还没看懂。能讲解下原理吗?
俩种方式,查表和计算法算crc tianluo 发表于 2012-9-6 19:21 static/image/common/back.gif
首先感谢你的程序,还没看懂。能讲解下原理吗?
俩种方式,查表和计算法算crc 写的不错哦!
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