Pratyush Mallick / Mbed OS nano_dac

this is testing

noos_mbed/util/crc8.c@0:e8a1ba50c46b, 2021-01-14 (annotated)

Committer:
pmallick
Date:
Thu Jan 14 19:12:57 2021 +0530
Revision:
0:e8a1ba50c46b
this is testing

Who changed what in which revision?

UserRevisionLine numberNew contents of line
pmallick 0:e8a1ba50c46b 1 /***************************************************************************//**
pmallick 0:e8a1ba50c46b 2 * @file crc8.c
pmallick 0:e8a1ba50c46b 3 * @brief Source file of CRC-8 computation.
pmallick 0:e8a1ba50c46b 4 * @author Darius Berghe (darius.berghe@analog.com)
pmallick 0:e8a1ba50c46b 5 ********************************************************************************
pmallick 0:e8a1ba50c46b 6 * Copyright 2020(c) Analog Devices, Inc.
pmallick 0:e8a1ba50c46b 7 *
pmallick 0:e8a1ba50c46b 8 * All rights reserved.
pmallick 0:e8a1ba50c46b 9 *
pmallick 0:e8a1ba50c46b 10 * Redistribution and use in source and binary forms, with or without
pmallick 0:e8a1ba50c46b 11 * modification, are permitted provided that the following conditions are met:
pmallick 0:e8a1ba50c46b 12 * - Redistributions of source code must retain the above copyright
pmallick 0:e8a1ba50c46b 13 * notice, this list of conditions and the following disclaimer.
pmallick 0:e8a1ba50c46b 14 * - Redistributions in binary form must reproduce the above copyright
pmallick 0:e8a1ba50c46b 15 * notice, this list of conditions and the following disclaimer in
pmallick 0:e8a1ba50c46b 16 * the documentation and/or other materials provided with the
pmallick 0:e8a1ba50c46b 17 * distribution.
pmallick 0:e8a1ba50c46b 18 * - Neither the name of Analog Devices, Inc. nor the names of its
pmallick 0:e8a1ba50c46b 19 * contributors may be used to endorse or promote products derived
pmallick 0:e8a1ba50c46b 20 * from this software without specific prior written permission.
pmallick 0:e8a1ba50c46b 21 * - The use of this software may or may not infringe the patent rights
pmallick 0:e8a1ba50c46b 22 * of one or more patent holders. This license does not release you
pmallick 0:e8a1ba50c46b 23 * from the requirement that you obtain separate licenses from these
pmallick 0:e8a1ba50c46b 24 * patent holders to use this software.
pmallick 0:e8a1ba50c46b 25 * - Use of the software either in source or binary form, must be run
pmallick 0:e8a1ba50c46b 26 * on or directly connected to an Analog Devices Inc. component.
pmallick 0:e8a1ba50c46b 27 *
pmallick 0:e8a1ba50c46b 28 * THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR
pmallick 0:e8a1ba50c46b 29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT,
pmallick 0:e8a1ba50c46b 30 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
pmallick 0:e8a1ba50c46b 31 * IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT,
pmallick 0:e8a1ba50c46b 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
pmallick 0:e8a1ba50c46b 33 * LIMITED TO, INTELLECTUAL PROPERTY RIGHTS, PROCUREMENT OF SUBSTITUTE GOODS OR
pmallick 0:e8a1ba50c46b 34 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
pmallick 0:e8a1ba50c46b 35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
pmallick 0:e8a1ba50c46b 36 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
pmallick 0:e8a1ba50c46b 37 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
pmallick 0:e8a1ba50c46b 38 *******************************************************************************/
pmallick 0:e8a1ba50c46b 39 #include "crc8.h"
pmallick 0:e8a1ba50c46b 40
pmallick 0:e8a1ba50c46b 41 /***************************************************************************//**
pmallick 0:e8a1ba50c46b 42 * @brief Creates the CRC-8 lookup table for a given polynomial.
pmallick 0:e8a1ba50c46b 43 *
pmallick 0:e8a1ba50c46b 44 * @param table - Pointer to a CRC-8 lookup table to write to.
pmallick 0:e8a1ba50c46b 45 * @param polynomial - msb-first representation of desired polynomial.
pmallick 0:e8a1ba50c46b 46 *
pmallick 0:e8a1ba50c46b 47 * Polynomials in CRC algorithms are typically represented as shown below.
pmallick 0:e8a1ba50c46b 48 *
pmallick 0:e8a1ba50c46b 49 * poly = x^8 + x^2 + x^1 + 1
pmallick 0:e8a1ba50c46b 50 *
pmallick 0:e8a1ba50c46b 51 * Using msb-first direction, x^7 maps to the msb.
pmallick 0:e8a1ba50c46b 52 *
pmallick 0:e8a1ba50c46b 53 * msb first: poly = (1)00000111 = 0x07
pmallick 0:e8a1ba50c46b 54 *
pmallick 0:e8a1ba50c46b 55 * @return None.
pmallick 0:e8a1ba50c46b 56 *******************************************************************************/
pmallick 0:e8a1ba50c46b 57 void crc8_populate_msb(uint8_t * table, const uint8_t polynomial)
pmallick 0:e8a1ba50c46b 58 {
pmallick 0:e8a1ba50c46b 59 if (!table)
pmallick 0:e8a1ba50c46b 60 return;
pmallick 0:e8a1ba50c46b 61
pmallick 0:e8a1ba50c46b 62 for (int16_t n = 0; n < CRC8_TABLE_SIZE; n++) {
pmallick 0:e8a1ba50c46b 63 uint8_t currByte = (uint8_t)n;
pmallick 0:e8a1ba50c46b 64 for (uint8_t bit = 0; bit < 8; bit++) {
pmallick 0:e8a1ba50c46b 65 if ((currByte & 0x80) != 0) {
pmallick 0:e8a1ba50c46b 66 currByte <<= 1;
pmallick 0:e8a1ba50c46b 67 currByte ^= polynomial;
pmallick 0:e8a1ba50c46b 68 } else {
pmallick 0:e8a1ba50c46b 69 currByte <<= 1;
pmallick 0:e8a1ba50c46b 70 }
pmallick 0:e8a1ba50c46b 71 }
pmallick 0:e8a1ba50c46b 72 table[n] = currByte;
pmallick 0:e8a1ba50c46b 73 }
pmallick 0:e8a1ba50c46b 74 }
pmallick 0:e8a1ba50c46b 75
pmallick 0:e8a1ba50c46b 76 /***************************************************************************//**
pmallick 0:e8a1ba50c46b 77 * @brief Computes the CRC-8 over a buffer of data.
pmallick 0:e8a1ba50c46b 78 *
pmallick 0:e8a1ba50c46b 79 * @param table - Pointer to a CRC-8 lookup table for the desired polynomial.
pmallick 0:e8a1ba50c46b 80 * @param pdata - Pointer to 8-bit data buffer.
pmallick 0:e8a1ba50c46b 81 * @param nbytes - Number of bytes to compute the CRC-8 over.
pmallick 0:e8a1ba50c46b 82 * @param crc - Initial value for the CRC-8 computation. Can be used to
pmallick 0:e8a1ba50c46b 83 * cascade calls to this function by providing a previous
pmallick 0:e8a1ba50c46b 84 * output of this function as the crc parameter.
pmallick 0:e8a1ba50c46b 85 *
pmallick 0:e8a1ba50c46b 86 * @return crc - Computed CRC-8 value.
pmallick 0:e8a1ba50c46b 87 *******************************************************************************/
pmallick 0:e8a1ba50c46b 88 uint8_t crc8(const uint8_t * table, const uint8_t *pdata, size_t nbytes,
pmallick 0:e8a1ba50c46b 89 uint8_t crc)
pmallick 0:e8a1ba50c46b 90 {
pmallick 0:e8a1ba50c46b 91 unsigned int idx;
pmallick 0:e8a1ba50c46b 92
pmallick 0:e8a1ba50c46b 93 while (nbytes--) {
pmallick 0:e8a1ba50c46b 94 idx = (crc ^ *pdata);
pmallick 0:e8a1ba50c46b 95 crc = (table[idx]) & 0xff;
pmallick 0:e8a1ba50c46b 96 pdata++;
pmallick 0:e8a1ba50c46b 97 }
pmallick 0:e8a1ba50c46b 98
pmallick 0:e8a1ba50c46b 99 return crc;
pmallick 0:e8a1ba50c46b 100 }