Alexandre Lemay / Mbed 2 deprecated APP4_FunTimes

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Dependencies:   mbed mbed-rtos

CRC.cpp@9:8f479f7c1b54, 2017-10-25 (annotated)

Committer:
ThierryLeonard
Date:
Wed Oct 25 05:43:13 2017 +0000
Revision:
9:8f479f7c1b54
Parent:
6:ac7c0ccf9b5d 
final???;

Who changed what in which revision?

UserRevisionLine numberNew contents of line
ThierryLeonard 6:ac7c0ccf9b5d 1 #include "CRC.h"
ThierryLeonard 6:ac7c0ccf9b5d 2
ThierryLeonard 6:ac7c0ccf9b5d 3 const unsigned short CRCPOLYNOM = 0x8005;
ThierryLeonard 6:ac7c0ccf9b5d 4
ThierryLeonard 6:ac7c0ccf9b5d 5 // The last two bytes of data corresponds to the remainder. If they are of 0,0, this function will return the remainder to put into them.
ThierryLeonard 6:ac7c0ccf9b5d 6 // If the two last bytes contains the crc received, the return should be of 0
ThierryLeonard 6:ac7c0ccf9b5d 7 int crc16Remainder(std::vector<unsigned char> data, unsigned short generator)
ThierryLeonard 6:ac7c0ccf9b5d 8 {
ThierryLeonard 6:ac7c0ccf9b5d 9 // shift generator
ThierryLeonard 6:ac7c0ccf9b5d 10 unsigned int polynom = generator << 16;
ThierryLeonard 6:ac7c0ccf9b5d 11
ThierryLeonard 6:ac7c0ccf9b5d 12 if (data.empty())
ThierryLeonard 6:ac7c0ccf9b5d 13 {
ThierryLeonard 6:ac7c0ccf9b5d 14 return -1;
ThierryLeonard 6:ac7c0ccf9b5d 15 }
ThierryLeonard 6:ac7c0ccf9b5d 16
ThierryLeonard 6:ac7c0ccf9b5d 17 unsigned int remainder = data[0] << 24 | data[1] << 16;
ThierryLeonard 6:ac7c0ccf9b5d 18
ThierryLeonard 6:ac7c0ccf9b5d 19 for (int i = 2; i < data.size(); i++)
ThierryLeonard 6:ac7c0ccf9b5d 20 {
ThierryLeonard 6:ac7c0ccf9b5d 21 remainder = remainder | data[i] << 8;
ThierryLeonard 6:ac7c0ccf9b5d 22 for (int j = 0; j < 8; j++)
ThierryLeonard 6:ac7c0ccf9b5d 23 {
ThierryLeonard 6:ac7c0ccf9b5d 24 // if msb is 1, shift and xor
ThierryLeonard 6:ac7c0ccf9b5d 25 if (remainder >> 31 ==1)
ThierryLeonard 6:ac7c0ccf9b5d 26 {
ThierryLeonard 6:ac7c0ccf9b5d 27 remainder = (remainder << 1) ^ polynom;
ThierryLeonard 6:ac7c0ccf9b5d 28 }
ThierryLeonard 6:ac7c0ccf9b5d 29 else
ThierryLeonard 6:ac7c0ccf9b5d 30 {
ThierryLeonard 6:ac7c0ccf9b5d 31 remainder = remainder << 1;
ThierryLeonard 6:ac7c0ccf9b5d 32 }
ThierryLeonard 6:ac7c0ccf9b5d 33 }
ThierryLeonard 6:ac7c0ccf9b5d 34 }
ThierryLeonard 6:ac7c0ccf9b5d 35 // Calculates remainder of last 16 bits
ThierryLeonard 6:ac7c0ccf9b5d 36 for (int i = 0; i < 16; i++)
ThierryLeonard 6:ac7c0ccf9b5d 37 {
ThierryLeonard 6:ac7c0ccf9b5d 38 // if msb is 1, shift and xor
ThierryLeonard 6:ac7c0ccf9b5d 39 if (remainder >> 31 == 1)
ThierryLeonard 6:ac7c0ccf9b5d 40 {
ThierryLeonard 6:ac7c0ccf9b5d 41 remainder = (remainder << 1) ^ polynom;
ThierryLeonard 6:ac7c0ccf9b5d 42 }
ThierryLeonard 6:ac7c0ccf9b5d 43 else
ThierryLeonard 6:ac7c0ccf9b5d 44 {
ThierryLeonard 6:ac7c0ccf9b5d 45 remainder = remainder << 1;
ThierryLeonard 6:ac7c0ccf9b5d 46 }
ThierryLeonard 6:ac7c0ccf9b5d 47 }
ThierryLeonard 6:ac7c0ccf9b5d 48 return remainder >> 16;
ThierryLeonard 6:ac7c0ccf9b5d 49
ThierryLeonard 6:ac7c0ccf9b5d 50 }