133 lines
3.1 KiB
C
133 lines
3.1 KiB
C
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/*
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* crc.c
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*
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* Created on: 7 <EFBFBD><EFBFBD><EFBFBD>. 2024 <EFBFBD>.
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* Author: seklyuts
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*/
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#include "f28x_project.h"
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const int order = 6;
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const unsigned long polynom = 0x43;
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const int direct = 1;
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const unsigned long crcinit = 0x0000;
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const unsigned long crcxor = 0xffff;
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const int refin = 0;
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const int refout = 0;
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// internal global values:
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unsigned long crcmask;
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unsigned long crchighbit;
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unsigned long crcinit_direct;
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unsigned long crcinit_nondirect;
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unsigned long crctab[256];
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unsigned long reflect (unsigned long crc, int bitnum) {
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// reflects the lower <20>bitnum<75> bits of <20>crc<72>
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unsigned long i, j=1, crcout=0;
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for (i=(unsigned long)1<<(bitnum-1); i; i>>=1) {
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if (crc & i) crcout|=j;
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j<<= 1;
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}
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return (crcout);
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}
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unsigned long crcbitbybit(unsigned char* p, unsigned long len) {
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// bit by bit algorithm with augmented zero bytes.
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// does not use lookup table, suited for polynom orders between 1...32.
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unsigned long i, j, c, bit;
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unsigned long crc = crcinit_nondirect;
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for (i=0; i<len; i++) {
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c = (unsigned long)*p++;
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if (refin) c = reflect(c, 8);
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for (j=0x80; j; j>>=1) {
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bit = crc & crchighbit;
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crc<<= 1;
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if (c & j) crc|= 1;
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if (bit) crc^= polynom;
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}
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}
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for (i=0; i<order; i++) {
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bit = crc & crchighbit;
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crc<<= 1;
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if (bit) crc^= polynom;
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}
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if (refout) crc=reflect(crc, order);
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crc^= crcxor;
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crc&= crcmask;
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return(crc);
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}
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//unsigned long crcbitbybitfast(unsigned char* p, unsigned long len) {
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uint16_t crcbitbybitfast(uint64_t data)
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{
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// fast bit by bit algorithm without augmented zero bytes.
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// does not use lookup table, suited for polynom orders between 1...32.
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unsigned long i, j, c, bit;
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unsigned long crc = crcinit_direct;
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crcmask = ((((uint64_t)1<<(order-1))-1)<<1)|1;
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crchighbit = (uint64_t)1<<(order-1);
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uint16_t p[5];
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p[4] = data & 0xFF;
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p[3] = (data >> 8) & 0xFF;
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p[2] = (data >> 16) & 0xFF;
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p[1] = (data >> 24) & 0xFF;
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p[0] = (data >> 32) & 0xFF;
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for (i=0; i<5; i++) {
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c = p[i];
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// if (refin) c = reflect(c, 8);
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for (j=0x80; j; j>>=1) {
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bit = crc & crchighbit;
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crc<<= 1;
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if (c & j) bit^= crchighbit;
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if (bit) crc^= polynom;
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}
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}
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// if (refout) crc=reflect(crc, order);
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crc^= crcxor;
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crc&= crcmask;
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return(crc);
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}
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#define ALL_BITS 38
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#define CS_BITS 6
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uint16_t calcCRC(uint64_t data) // 38 bit -> 6 bit // x6 + x1 + 1/// poly = 0b1000011 = 0x86;
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{
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uint64_t temp1, temp2, crc = 0;
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uint64_t poly = (uint64_t)0b1000011 << (ALL_BITS - CS_BITS - 1);
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uint16_t i = 0;
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crc = poly;
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temp1 = data;
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crc ^= temp1;
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for(i=0; i < (ALL_BITS - CS_BITS); i++)
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{
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// crc = (crc & ((uint64_t)1 << (ALL_BITS-1))) ? ((crc ^ poly) << 1) : (crc << 1);
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temp2 = ((uint64_t)1 << (ALL_BITS-1));
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if(crc & temp2)
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{
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crc = ((crc ^ poly) << 1);
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}
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else
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{
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crc = (crc << 1);
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}
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}
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return (crc >> (ALL_BITS - CS_BITS));
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}
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