1 // Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #ifndef ROM_CRC_H 16 #define ROM_CRC_H 17 18 #include <stdint.h> 19 20 #ifdef __cplusplus 21 extern "C" { 22 #endif 23 24 /** \defgroup uart_apis, uart configuration and communication related apis 25 * @brief uart apis 26 */ 27 28 /** @addtogroup uart_apis 29 * @{ 30 */ 31 32 33 /* Notes about CRC APIs usage 34 * The ESP32 ROM include some CRC tables and CRC APIs to speed up CRC calculation. 35 * The CRC APIs include CRC8, CRC16, CRC32 algorithms for both little endian and big endian modes. 36 * Here are the polynomials for the algorithms: 37 * CRC-8 x8+x2+x1+1 0x07 38 * CRC16-CCITT x16+x12+x5+1 0x1021 39 * CRC32 x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x1+1 0x04c11db7 40 * 41 * These group of CRC APIs are designed to calculate the data in buffers either continuous or not. 42 * To make it easy, we had added a `~` at the beginning and the end of the functions. 43 * To calculate non-continuous buffers, we can write the code like this: 44 * init = ~init; 45 * crc = crc32_le(init, buf0, length0); 46 * crc = crc32_le(crc, buf1, length1); 47 * crc = ~crc; 48 * 49 * However, it is not easy to select which API to use and give the correct parameters. 50 * A specific CRC algorithm will include this parameters: width, polynomials, init, refin, refout, xorout 51 * refin and refout show the endian of the algorithm: 52 * if both of them are true, please use the little endian API. 53 * if both of them are false, please use the big endian API. 54 * xorout is the value which you need to be xored to the raw result. 55 * However, these group of APIs need one '~' before and after the APIs. 56 * 57 * Here are some examples for CRC16: 58 * CRC-16/CCITT, poly = 0x1021, init = 0x0000, refin = true, refout = true, xorout = 0x0000 59 * crc = ~crc16_le((uint16_t)~0x0000, buf, length); 60 * 61 * CRC-16/CCITT-FALSE, poly = 0x1021, init = 0xffff, refin = false, refout = false, xorout = 0x0000 62 * crc = ~crc16_be((uint16_t)~0xffff, buf, length); 63 * 64 * CRC-16/X25, poly = 0x1021, init = 0xffff, refin = true, refout = true, xorout = 0xffff 65 * crc = (~crc16_le((uint16_t)~(0xffff), buf, length))^0xffff; 66 * 67 * CRC-16/XMODEM, poly= 0x1021, init = 0x0000, refin = false, refout = false, xorout = 0x0000 68 * crc = ~crc16_be((uint16_t)~0x0000, buf, length); 69 * 70 * 71 */ 72 73 /** 74 * @brief CRC32 value that is in little endian. 75 * 76 * @param uint32_t crc : init crc value, use 0 at the first use. 77 * 78 * @param uint8_t const *buf : buffer to start calculate crc. 79 * 80 * @param uint32_t len : buffer length in byte. 81 * 82 * @return None 83 */ 84 uint32_t crc32_le(uint32_t crc, uint8_t const *buf, uint32_t len); 85 86 /** 87 * @brief CRC32 value that is in big endian. 88 * 89 * @param uint32_t crc : init crc value, use 0 at the first use. 90 * 91 * @param uint8_t const *buf : buffer to start calculate crc. 92 * 93 * @param uint32_t len : buffer length in byte. 94 * 95 * @return None 96 */ 97 uint32_t crc32_be(uint32_t crc, uint8_t const *buf, uint32_t len); 98 99 /** 100 * @brief CRC16 value that is in little endian. 101 * 102 * @param uint16_t crc : init crc value, use 0 at the first use. 103 * 104 * @param uint8_t const *buf : buffer to start calculate crc. 105 * 106 * @param uint32_t len : buffer length in byte. 107 * 108 * @return None 109 */ 110 uint16_t crc16_le(uint16_t crc, uint8_t const *buf, uint32_t len); 111 112 /** 113 * @brief CRC16 value that is in big endian. 114 * 115 * @param uint16_t crc : init crc value, use 0 at the first use. 116 * 117 * @param uint8_t const *buf : buffer to start calculate crc. 118 * 119 * @param uint32_t len : buffer length in byte. 120 * 121 * @return None 122 */ 123 uint16_t crc16_be(uint16_t crc, uint8_t const *buf, uint32_t len); 124 125 /** 126 * @brief CRC8 value that is in little endian. 127 * 128 * @param uint8_t crc : init crc value, use 0 at the first use. 129 * 130 * @param uint8_t const *buf : buffer to start calculate crc. 131 * 132 * @param uint32_t len : buffer length in byte. 133 * 134 * @return None 135 */ 136 uint8_t crc8_le(uint8_t crc, uint8_t const *buf, uint32_t len); 137 138 /** 139 * @brief CRC8 value that is in big endian. 140 * 141 * @param uint32_t crc : init crc value, use 0 at the first use. 142 * 143 * @param uint8_t const *buf : buffer to start calculate crc. 144 * 145 * @param uint32_t len : buffer length in byte. 146 * 147 * @return None 148 */ 149 uint8_t crc8_be(uint8_t crc, uint8_t const *buf, uint32_t len); 150 151 /** 152 * @} 153 */ 154 155 #ifdef __cplusplus 156 } 157 #endif 158 159 160 #endif 161
