SPI CRC calculation for polynom 0x8005

[stst9184]

Posted on March 23, 2012 at 19:09

I'm lost with my calculation of crc for 16 bit transmit mode, with a polynom 0x8005, init = 0x0000. I am calculating in Matlab a lookup table first, which seems all right:

0000 8005 800F 000A 801B 001E 0014 8011 8033 0036 003C 8039 0028 802D 8027 0022 8063 0066 006C 8069 0078 807D 8077 0072 0050 8055 805F 005A 804B 004E 0044 8041 80C3 00C6 00CC 80C9 00D8 80DD 80D7 00D2 00F0 80F5 80FF 00FA 80EB 00EE 00E4 80E1 00A0 80A5 80AF 00AA 80BB 00BE 00B4 80B1 8093 0096 009C 8099 0088 808D 8087 0082 8183 0186 018C 8189 0198 819D 8197 0192 01B0 81B5 81BF 01BA 81AB 01AE 01A4 81A1 01E0 81E5 81EF 01EA 81FB 01FE 01F4 81F1 81D3 01D6 01DC 81D9 01C8 81CD 81C7 01C2 0140 8145 814F 014A 815B 015E 0154 8151 8173 0176 017C 8179 0168 816D 8167 0162 8123 0126 012C 8129 0138 813D 8137 0132 0110 8115 811F 011A 810B 010E 0104 8101 8303 0306 030C 8309 0318 831D 8317 0312 0330 8335 833F 033A 832B 032E 0324 8321 0360 8365 836F 036A 837B 037E 0374 8371 8353 0356 035C 8359 0348 834D 8347 0342 03C0 83C5 83CF 03CA 83DB 03DE 03D4 83D1 83F3 03F6 03FC 83F9 03E8 83ED 83E7 03E2 83A3 03A6 03AC 83A9 03B8 83BD 83B7 03B2 0390 8395 839F 039A 838B 038E 0384 8381 0280 8285 828F 028A 829B 029E 0294 8291 82B3 02B6 02BC 82B9 02A8 82AD 82A7 02A2 82E3 02E6 02EC 82E9 02F8 82FD 82F7 02F2 02D0 82D5 82DF 02DA 82CB 02CE 02C4 82C1 8243 0246 024C 8249 0258 825D 8257 0252 0270 8275 827F 027A 826B 026E 0264 8261 0220 8225 822F 022A 823B 023E 0234 8231 8213 0216 021C 8219 0208 820D 8207 0202 After that I caclulate a CRC for a byte stream so :

remainder = uint16(0); 

nByteData = length(byteData);


for iByte = 1:1:nByteData;

data = uint8(bitxor(uint16(byteData(iByte)), bitshift(remainder , -(obj.WIDTH - 8), 16)));

remainder = uint16(bitxor(obj.crc16Lookup(data+1), bitshift(remainder , -8, 16)));

end


value = remainder;

However I do not get a same CRC as a SPI unit. Example: spiFrame = 'FB310100020003000400050006000700080009000a000b000c000d000e000f00100011001200'; (SPI CRC=0xAECC, Matlab CRC=0x2FCE). What am I doing wrong? Fos some other streams it is OK:( Can somebody help me? #spi #crc16

[stst9184]

Posted on March 27, 2012 at 09:51

Solution:

1.
for byte = byteData
2.
crcLookupIndex = bitxor(bitand(bitshift(crc, -8, 16), uint16(hex2dec('00FF'))), uint16(byte));
3.
crc = bitxor(bitand(bitshift(crc, 8, 16), uint16(hex2dec('FF00'))), obj.crc16Lookup(crcLookupIndex+1)); 
4.
end