crc-8 dow table generation problem

Sep 04, 2006 4 Replies

Rate this thread:

phesx 19 years ago

Hi to all, I have a problem with crc-8 dow algoritmic. x^8+x^5+x^4+1 CRC_DOW

The problem is: I want implement the fast calculation but My CRC_table is different from the CRC_DOWN table reported in the web

description: looking at the web I've founf the CRC table to calculate CRC_DOW (below an extract ... 0-15)

CRC_DOWN right table (decimal format):

0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31,
65, ................

My WRONG table is (decimal format):

0, 49, 98, 83, 196, 245 .........

In order to generate the CRC table I use the code below:

#define CRC8_POLYNOMIAL 0x131 // x^8+x^5+x^4+1 0001 0011 0001 CRC_DOW int i, j; unsigned int crc8; for(i = 0 ; i < 256; i++){ crc8 = i; for(j = 8; j > 0; j--){ if(crc8 & 0x80){ crc8 = (crc8

Vote

Dan Henry 19 years ago

===SNIP===

Yes, try the other way around:

#include

#define POLY 0x8C

void main(void) { int index; int i; unsigned x; unsigned temp;

for (index = 0; index < 256; ++index) { temp = index;

for (i = 0; i < 8; ++i) { x = temp & 1; temp >>= 1;

if (x != 0) temp ^= POLY; }

printf("0x%02X, ", temp); if ((index & 7) == 7) putchar('\n'); } }

Dan Henry

Vote

phesx 19 years ago

thanks for your support Dan

Dan Henry ha scritto:

Vote

Dan Henry 19 years ago

Please, ignore the "void main" stuff if you can. The important part is the POLY and inner "for" loop.

Dan Henry

Vote

HKJ 19 years ago

...

Maybe this list of crc code can help:

formatting link

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required