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Dependencies:   FreescaleIAP mbed-rtos mbed

Fork of RAJANGAM_REVIEW_BAE_CODE by Team Fox

crc.h@20:949d13045431, 2016-07-01 (annotated)

Committer:
lakshya
Date:
Fri Jul 01 17:55:30 2016 +0000
Revision:
20:949d13045431
Parent:
19:79e69017c855 
BAE final 1.0 (1st july); ; BCN and EPS  code to be upgraded; +; testing and troubleshooting to be done ; +; watchdog to be implemented; ; comparing with flowcharts.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
sakthipriya 3:07e15677a75c 1 //EDITS
sakthipriya 3:07e15677a75c 2 //changed the initial remainder from 0x0000 to 0xffff according to the standards
sakthipriya 3:07e15677a75c 3 //made two seperate functions crc16_gen and crc8_gen
sakthipriya 3:07e15677a75c 4
sakthipriya 3:07e15677a75c 5 #define TOPBIT16 (1 << 15)
sakthipriya 3:07e15677a75c 6 #define TOPBIT8 (1 << 7)
sakthipriya 3:07e15677a75c 7 #define POLYNOMIAL16 0x1021
sakthipriya 3:07e15677a75c 8 #define POLYNOMIAL8 0xEA
sakthipriya 3:07e15677a75c 9
lakshya 19:79e69017c855 10 namespace CRC
lakshya 19:79e69017c855 11 {
lakshya 20:949d13045431 12 typedef uint16_t crctype16;
lakshya 19:79e69017c855 13 crctype16 crc16_gen(const unsigned char message[], unsigned int nBytes)
lakshya 19:79e69017c855 14 {
lakshya 19:79e69017c855 15 crctype16 remainder = 0xffff;
lakshya 19:79e69017c855 16 int byte;
lakshya 19:79e69017c855 17 char bit;
sakthipriya 3:07e15677a75c 18
lakshya 19:79e69017c855 19 for( byte = 0 ; byte < nBytes ; byte++ )
lakshya 19:79e69017c855 20 {
lakshya 19:79e69017c855 21 /*
lakshya 19:79e69017c855 22 Bring the data byte by byte
lakshya 19:79e69017c855 23 each time only one byte is brought
lakshya 19:79e69017c855 24 0 xor x = x
lakshya 19:79e69017c855 25 */
lakshya 19:79e69017c855 26 remainder = remainder ^ ( message[byte] << 8 );
sakthipriya 3:07e15677a75c 27
lakshya 19:79e69017c855 28 for( bit = 8 ; bit > 0 ; bit--)
lakshya 19:79e69017c855 29 {
lakshya 19:79e69017c855 30 /*
lakshya 19:79e69017c855 31 for each bit, xor the remainder with polynomial
lakshya 19:79e69017c855 32 if the MSB is 1
lakshya 19:79e69017c855 33 */
lakshya 19:79e69017c855 34 if(remainder & TOPBIT16)
lakshya 19:79e69017c855 35 {
lakshya 19:79e69017c855 36 remainder = (remainder << 1) ^ POLYNOMIAL16;
lakshya 19:79e69017c855 37 /*
lakshya 19:79e69017c855 38 each time the remainder is xor-ed with polynomial, the MSB is made zero
lakshya 19:79e69017c855 39 hence the first digit of the remainder is ignored in the loop
lakshya 19:79e69017c855 40 */
lakshya 19:79e69017c855 41 }
lakshya 19:79e69017c855 42 else
lakshya 19:79e69017c855 43 {
lakshya 19:79e69017c855 44 remainder = (remainder << 1);
lakshya 19:79e69017c855 45 }
lakshya 19:79e69017c855 46 }
sakthipriya 3:07e15677a75c 47 }
lakshya 19:79e69017c855 48
lakshya 19:79e69017c855 49 return remainder;
sakthipriya 3:07e15677a75c 50 }
lakshya 20:949d13045431 51
lakshya 20:949d13045431 52
sakthipriya 3:07e15677a75c 53 typedef uint8_t crctype8;
lakshya 19:79e69017c855 54 crctype8 crc8_gen(const unsigned char message[], unsigned int nBytes)
lakshya 19:79e69017c855 55 {
lakshya 19:79e69017c855 56 crctype8 remainder = 0xff;
sakthipriya 3:07e15677a75c 57
lakshya 19:79e69017c855 58 for(int byte = 0 ; byte < nBytes ; byte++ )
lakshya 19:79e69017c855 59 {
lakshya 19:79e69017c855 60 /*
lakshya 19:79e69017c855 61 Bring the data byte by byte
lakshya 19:79e69017c855 62 each time only one byte is brought
lakshya 19:79e69017c855 63 0 xor x = x
lakshya 19:79e69017c855 64 */
lakshya 19:79e69017c855 65 remainder = remainder ^ ( message[byte] );
sakthipriya 3:07e15677a75c 66
lakshya 19:79e69017c855 67 for(int bit = 8 ; bit > 0 ; bit--)
lakshya 19:79e69017c855 68 {
lakshya 19:79e69017c855 69 /*
lakshya 19:79e69017c855 70 for each bit, xor the remainder with polynomial
lakshya 19:79e69017c855 71 if the MSB is 1
lakshya 19:79e69017c855 72 */
lakshya 19:79e69017c855 73 if(remainder & TOPBIT8)
lakshya 19:79e69017c855 74 {
lakshya 19:79e69017c855 75 remainder = (remainder << 1) ^ POLYNOMIAL8;
lakshya 19:79e69017c855 76 /*
lakshya 19:79e69017c855 77 each time the remainder is xor-ed with polynomial, the MSB is made zero
lakshya 19:79e69017c855 78 hence the first digit of the remainder is ignored in the loop
lakshya 19:79e69017c855 79 */
lakshya 19:79e69017c855 80 }
lakshya 19:79e69017c855 81 else
lakshya 19:79e69017c855 82 {
lakshya 19:79e69017c855 83 remainder = (remainder << 1);
lakshya 19:79e69017c855 84 }
lakshya 19:79e69017c855 85 }
sakthipriya 3:07e15677a75c 86 }
lakshya 19:79e69017c855 87
lakshya 19:79e69017c855 88 return remainder;
sakthipriya 3:07e15677a75c 89 }
sakthipriya 3:07e15677a75c 90 }