161 lines
4.9 KiB
C
161 lines
4.9 KiB
C
// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ROM_CRC_H
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#define ROM_CRC_H
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** \defgroup uart_apis, uart configuration and communication related apis
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* @brief uart apis
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*/
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/** @addtogroup uart_apis
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* @{
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*/
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/* Notes about CRC APIs usage
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* The ESP32 ROM include some CRC tables and CRC APIs to speed up CRC calculation.
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* The CRC APIs include CRC8, CRC16, CRC32 algorithms for both little endian and big endian modes.
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* Here are the polynomials for the algorithms:
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* CRC-8 x8+x2+x1+1 0x07
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* CRC16-CCITT x16+x12+x5+1 0x1021
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* CRC32 x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x1+1 0x04c11db7
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*
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* These group of CRC APIs are designed to calculate the data in buffers either continuous or not.
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* To make it easy, we had added a `~` at the beginning and the end of the functions.
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* To calculate non-continuous buffers, we can write the code like this:
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* init = ~init;
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* crc = crc32_le(init, buf0, length0);
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* crc = crc32_le(crc, buf1, length1);
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* crc = ~crc;
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*
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* However, it is not easy to select which API to use and give the correct parameters.
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* A specific CRC algorithm will include this parameters: width, polynomials, init, refin, refout, xorout
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* refin and refout show the endian of the algorithm:
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* if both of them are true, please use the little endian API.
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* if both of them are false, please use the big endian API.
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* xorout is the value which you need to be xored to the raw result.
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* However, these group of APIs need one '~' before and after the APIs.
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*
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* Here are some examples for CRC16:
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* CRC-16/CCITT, poly = 0x1021, init = 0x0000, refin = true, refout = true, xorout = 0x0000
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* crc = ~crc16_le((uint16_t)~0x0000, buf, length);
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*
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* CRC-16/CCITT-FALSE, poly = 0x1021, init = 0xffff, refin = false, refout = false, xorout = 0x0000
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* crc = ~crc16_be((uint16_t)~0xffff, buf, length);
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*
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* CRC-16/X25, poly = 0x1021, init = 0xffff, refin = true, refout = true, xorout = 0xffff
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* crc = (~crc16_le((uint16_t)~(0xffff), buf, length))^0xffff;
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*
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* CRC-16/XMODEM, poly= 0x1021, init = 0x0000, refin = false, refout = false, xorout = 0x0000
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* crc = ~crc16_be((uint16_t)~0x0000, buf, length);
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*
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*
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*/
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/**
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* @brief CRC32 value that is in little endian.
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*
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* @param uint32_t crc : init crc value, use 0 at the first use.
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*
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* @param uint8_t const *buf : buffer to start calculate crc.
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*
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* @param uint32_t len : buffer length in byte.
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*
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* @return None
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*/
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uint32_t crc32_le(uint32_t crc, uint8_t const *buf, uint32_t len);
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/**
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* @brief CRC32 value that is in big endian.
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*
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* @param uint32_t crc : init crc value, use 0 at the first use.
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*
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* @param uint8_t const *buf : buffer to start calculate crc.
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*
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* @param uint32_t len : buffer length in byte.
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*
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* @return None
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*/
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uint32_t crc32_be(uint32_t crc, uint8_t const *buf, uint32_t len);
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/**
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* @brief CRC16 value that is in little endian.
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*
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* @param uint16_t crc : init crc value, use 0 at the first use.
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*
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* @param uint8_t const *buf : buffer to start calculate crc.
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*
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* @param uint32_t len : buffer length in byte.
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*
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* @return None
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*/
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uint16_t crc16_le(uint16_t crc, uint8_t const *buf, uint32_t len);
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/**
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* @brief CRC16 value that is in big endian.
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*
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* @param uint16_t crc : init crc value, use 0 at the first use.
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*
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* @param uint8_t const *buf : buffer to start calculate crc.
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*
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* @param uint32_t len : buffer length in byte.
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*
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* @return None
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*/
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uint16_t crc16_be(uint16_t crc, uint8_t const *buf, uint32_t len);
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/**
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* @brief CRC8 value that is in little endian.
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*
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* @param uint8_t crc : init crc value, use 0 at the first use.
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*
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* @param uint8_t const *buf : buffer to start calculate crc.
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*
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* @param uint32_t len : buffer length in byte.
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*
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* @return None
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*/
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uint8_t crc8_le(uint8_t crc, uint8_t const *buf, uint32_t len);
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/**
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* @brief CRC8 value that is in big endian.
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*
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* @param uint32_t crc : init crc value, use 0 at the first use.
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*
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* @param uint8_t const *buf : buffer to start calculate crc.
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*
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* @param uint32_t len : buffer length in byte.
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*
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* @return None
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*/
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uint8_t crc8_be(uint8_t crc, uint8_t const *buf, uint32_t len);
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/**
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* @}
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*/
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#ifdef __cplusplus
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}
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#endif
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#endif
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