src/main/drivers/1-wire/ds_crc.c

   1
   2 #include <stdint.h>
   3
   4 uint8_t ds_crc8_bit_update(uint8_t crc8, uint8_t bit)
   5 {
   6     uint8_t crc8_base = (crc8 >> 1) & 0x73;
   7     uint8_t xor1 = (crc8 & 1) ^ bit;
   8     return crc8_base | ((((crc8 >> 3) & 1) ^ xor1) << 2) | ((((crc8 >> 4) & 1) ^ xor1) << 3) | (xor1 << 7);
   9 }
  10
  11 uint8_t ds_crc8_byte_update(uint8_t crc8, uint8_t byte)
  12 {
  13     for (uint8_t i = 0; i < 8; ++i) {
  14         uint8_t mix = (crc8 ^ byte) & 0x01;
  15         crc8 >>= 1;
  16         if (mix) crc8 ^= 0x8C;
  17         byte >>= 1;
  18     }
  19     return crc8;
  20 }
  21
  22 uint8_t ds_crc8(const uint8_t *addr, uint8_t len)
  23 {
  24      uint8_t crc8 = 0;
  25      for (uint8_t i=0; i < len; ++i) crc8 = ds_crc8_byte_update(crc8, addr[i]);
  26      return crc8;
  27 }
  28