C++ (Cpp) crc_calc_block_crc8 Examples

Example #1

File: fms_spi_link.c Project: 1bitsquared/paparazzi

int spi_link_send(void *buf_out, size_t count, void *buf_in, uint8_t* crc_valid) {

  int ret;

  struct spi_ioc_transfer tr = {
    .tx_buf        = (unsigned long)buf_out,
    .rx_buf        = (unsigned long)buf_in,
    .len           = count,
    .delay_usecs   = spi_link.delay,
    .speed_hz      = spi_link.speed,
    .bits_per_word = spi_link.bits,
  };

  ((uint8_t*)buf_out)[count-1] = crc_calc_block_crc8(buf_out, count-1);
  ret = ioctl(spi_link.fd, SPI_IOC_MESSAGE(1), &tr);
  spi_link.msg_cnt++;

  uint8_t computed_crc = crc_calc_block_crc8(buf_in, count-1);
  if (computed_crc == ((uint8_t*)buf_in)[count-1])
    *crc_valid = 1;
  else {
    *crc_valid = 0;
    spi_link.crc_err_cnt++;
  }

  return ret;

}


#define POLYNOMIAL 0x31
#define WIDTH  (8 * sizeof(uint8_t))
#define TOPBIT (1 << (WIDTH - 1))
uint8_t crc_calc_block_crc8(const uint8_t buf[], uint32_t len) {
  uint8_t  _remainder = 0;
  for (uint32_t byte = 0; byte < len; ++byte)  {
    _remainder ^= (buf[byte] << (WIDTH - 8));
    for (uint8_t bit = 8; bit > 0; --bit)  {
      if (_remainder & TOPBIT)
        _remainder = (_remainder << 1) ^ POLYNOMIAL;
      else
        _remainder = (_remainder << 1);
    }
  }
  return (_remainder);
}

Example #2

File: overo_test_spi_link.c Project: Paolo-Maffei/lxyppc-tetrix

int main(int argc, char *argv[]) {

  uint32_t us_delay;

  if(argc > 1) {
    us_delay = atoi(argv[1]);
  }
  else {
    us_delay = 1953;
  }

  printf("Delay: %dus\n", us_delay);

  if (spi_link_init()) {
    TRACE(TRACE_ERROR, "%s", "failed to open SPI link \n");
    return -1;
  }

  uint8_t skip_buf_check = 0;
  uint8_t skip_crc_check = 0;

  uint32_t buf_check_errors = 0;

  while (1) {
    struct AutopilotMessageCRCFrame crc_msg_out;
    struct AutopilotMessageCRCFrame msg_out_prev;
    struct AutopilotMessageCRCFrame crc_msg_in;
    uint8_t crc_valid;

    /* backup message for later comparison */
    memcpy(&msg_out_prev, &crc_msg_out, sizeof(struct AutopilotMessageCRCFrame));
    /* fill message with data */
    fill_msg(&crc_msg_out);
    /* send it over spi */
    spi_link_send(&crc_msg_out, sizeof(struct AutopilotMessageCRCFrame), &crc_msg_in, &crc_valid);

    /* check that received message is identical to the one previously sent */
    if (!skip_buf_check && spi_link.msg_cnt > 1) {
      if (memcmp(&crc_msg_in.payload, &msg_out_prev.payload, sizeof(struct OVERO_LINK_MSG_DOWN))) {
	printf("Compare failed: (received != expected): \n");
	print_up_msg(&crc_msg_in);
	print_down_msg(&msg_out_prev);
	buf_check_errors++;
      }
    }
    /* report crc error */
    if (!skip_crc_check & !crc_valid) {
      printf("CRC checksum failed: received %04X != computed %04X\n",
	     crc_msg_in.crc,
	     crc_calc_block_crc8((uint8_t*)&crc_msg_in.payload, sizeof(struct OVERO_LINK_MSG_DOWN)));
    }
    /* report message count */
    if (!(spi_link.msg_cnt % 1000))
      printf("msg %d, buf err %d, CRC errors: %d\n", spi_link.msg_cnt,
	     buf_check_errors, spi_link.crc_err_cnt);

    /* give it some rest */
    if(us_delay > 0)
      usleep(us_delay);
  }

  return 0;
}