a serial library to communicate with pebble time's smart strap interface
Dependents: xadow_smartstrap_for_pebble
crc.c
- Committer:
- KillingJacky
- Date:
- 2015-11-04
- Revision:
- 0:e4dad9e53f06
File content as of revision 0:e4dad9e53f06:
#include "crc.h" void crc8_calculate_byte_streaming(const uint8_t data, uint8_t *crc) { // Optimal polynomial chosen based on // http://users.ece.cmu.edu/~koopman/roses/dsn04/koopman04_crc_poly_embedded.pdf // Note that this is different than the standard CRC-8 polynomial, because the // standard CRC-8 polynomial is not particularly good. // nibble lookup table for (x^8 + x^5 + x^3 + x^2 + x + 1) static const uint8_t lookup_table[] = { 0, 47, 94, 113, 188, 147, 226, 205, 87, 120, 9, 38, 235, 196, 181, 154 }; int i; for (i = 2; i > 0; i--) { uint8_t nibble = data; if (i % 2 == 0) { nibble >>= 4; } int index = nibble ^ (*crc >> 4); *crc = lookup_table[index & 0xf] ^ (*crc << 4); } }