I want to implement CRC-16/X-25. I have a code written in C for CRC-16/CCITT_FALSE, but I don't know what changes do I need to make in that code for CRC-16/X-25 implementation?
The code I am using for CRC-16/CCITT-FALSE is given below:
#include #define CRC_POLYNOMIAL 0x1021 #define USHORT_TOPBIT 0x8000 short crc_ret; // function initialisation unsigned short crc16(const char *buf, unsigned int buf_len) { unsigned short ret = 0xFFFF; // Initial Value int bit = 8; do { if (!buf) { break; } unsigned int i = 0; for (i=0; i> 8)); for (bit = 8; bit > 0; --bit) { if (ret & USHORT_TOPBIT) ret = (unsigned short)((ret >> 1) ^ CRC_POLYNOMIAL); else ret = (unsigned short)(ret >> 1); } } } while (0); return ret; } int main(void) { PM5CTL0 &= ~LOCKLPM5; // Disable the GPIO power-on default high-impedance mode to activate // previously configured port settings char buf[16]; buf[0] = 0x5A; //buf[0], buf[1] and buf[2] are data bytes buf[1] = 0xCF; buf[2] = 0x00; crc_ret = crc16(buf, 3); // Calling CRC function }
Any help would be highly appreciated
Have a look at sec. 2.2.7.4 in https://www.itu.int/rec/T-REC-X.25-199610-I/en
the crc is defined. It's called FCS there but I expect it to be the same thing.
Maybe it's just my browser but the way the formatting of the code looks, you can not expect anybody to try to read that.
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