| 1 | function crcOut = calcCRC32(thePacketBytes) |
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| 2 | %Based on the C code example at: |
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| 3 | %http://www.netrino.com/Embedded-Systems/How-To/CRC-Calculation-C-Code |
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| 4 | %Uses slightly modified version of CRC-32: |
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| 5 | % No output XOR |
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| 6 | % No bit-order swapping on message or digest bytes |
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| 7 | |
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| 8 | CRCPolynomial = hex2dec('04c11db7'); |
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| 9 | CRC_Table = CRC_table_gen(CRCPolynomial, 32); |
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| 10 | |
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| 11 | init_crc = hex2dec('ffffffff'); |
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| 12 | myData = thePacketBytes; |
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| 13 | %de2bi(49,'left-msb',8)) |
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| 14 | crc_accum = init_crc; |
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| 15 | for n=1:length(myData) |
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| 16 | x = bitshift(crc_accum,-24,32); |
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| 17 | %CRC32 would swap bit order here: |
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| 18 | % x = bitxor(x, bi2de( de2bi(myData(n),'left-msb',8))); |
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| 19 | x = bitxor(x, myData(n)); |
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| 20 | x = bitand(x,hex2dec('ff')); |
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| 21 | crc_accum = bitxor(bitshift(crc_accum,8,32),CRC_Table(x+1)); |
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| 22 | crc_tracking(n) = crc_accum; |
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| 23 | end |
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| 24 | |
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| 25 | CRC32 = crc_accum; |
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| 26 | %CRC32 would XOR with all ones, then reorder bits here: |
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| 27 | %CRC32 = bitxor(CRC32, hex2dec('ffffffff')); |
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| 28 | %CRC32 = bi2de(de2bi(CRC32,'left-msb',32)); |
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| 29 | |
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| 30 | CRC32_b3 = bitand(bitshift(CRC32,-24,32),hex2dec('ff')); |
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| 31 | CRC32_b2 = bitand(bitshift(CRC32,-16,32),hex2dec('ff')); |
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| 32 | CRC32_b1 = bitand(bitshift(CRC32,-8,32),hex2dec('ff')); |
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| 33 | CRC32_b0 = bitand(CRC32,hex2dec('ff')); |
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| 34 | |
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| 35 | crcOut = [CRC32_b3 CRC32_b2 CRC32_b1 CRC32_b0]; |
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