From: Nathael Pajani Date: Mon, 8 May 2017 00:03:55 +0000 (+0200) Subject: Add a CRC CCITT function for use with SSD/MMC driver. X-Git-Url: http://git.techno-innov.fr/?a=commitdiff_plain;h=be48b4f8adf3f0d4c56898d906b2276adf8f5800;p=soft%2Flpc122x%2Fcore Add a CRC CCITT function for use with SSD/MMC driver. --- diff --git a/include/lib/crc_ccitt.h b/include/lib/crc_ccitt.h new file mode 100644 index 0000000..a61b733 --- /dev/null +++ b/include/lib/crc_ccitt.h @@ -0,0 +1,34 @@ +/**************************************************************************** + * lib/crc_ccitt.h + * + * Copyright 2017 Nathael Pajani + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see . + * + *************************************************************************** */ + +#include "lib/stdint.h" + +/***************************************************************************** */ +/* CRC CCITT computation, using the above static lookup table for performance. + * If called for the first time for a given set of chunks of data, provide the + * start value (usually 0x0000, 0xFFFF or 0x1D0F) as crc parameter. + * Provide the previous crc value returned for each successive call corresponding to + * a new chunk of data in a given set. + * buf is a pointer to the buffer holding the data, and len the length of the data in + * the buffer. + * Returns the updated crc if buf is not null, or the old value when buff is null. + */ +uint16_t crc_ccitt(uint16_t crc, uint8_t* buf, int len); + diff --git a/lib/crc_ccitt.c b/lib/crc_ccitt.c new file mode 100644 index 0000000..d441c87 --- /dev/null +++ b/lib/crc_ccitt.c @@ -0,0 +1,106 @@ +/**************************************************************************** + * lib/crc_ccitt.c + * + * Copyright 2017 Nathael Pajani + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see . + * + *************************************************************************** */ + +#include "lib/stddef.h" +#include "lib/stdint.h" + +static const uint16_t crc_ccitt_table[256] = { + 0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7, 0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef, + 0x1231, 0x0210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6, 0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de, + 0x2462, 0x3443, 0x0420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485, 0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d, + 0x3653, 0x2672, 0x1611, 0x0630, 0x76d7, 0x66f6, 0x5695, 0x46b4, 0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc, + 0x48c4, 0x58e5, 0x6886, 0x78a7, 0x0840, 0x1861, 0x2802, 0x3823, 0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b, + 0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0x0a50, 0x3a33, 0x2a12, 0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a, + 0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0x0c60, 0x1c41, 0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49, + 0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0x0e70, 0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78, + 0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f, 0x1080, 0x00a1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067, + 0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e, 0x02b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256, + 0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d, 0x34e2, 0x24c3, 0x14a0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405, + 0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c, 0x26d3, 0x36f2, 0x0691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634, + 0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab, 0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x08e1, 0x3882, 0x28a3, + 0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a, 0x4a75, 0x5a54, 0x6a37, 0x7a16, 0x0af1, 0x1ad0, 0x2ab3, 0x3a92, + 0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9, 0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0x0cc1, + 0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8, 0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0x0ed1, 0x1ef0, +}; + + +/***************************************************************************** */ +/* CRC CCITT computation, using the above static lookup table for performance. + * If called for the first time for a given set of chunks of data, provide the + * start value (usually 0x0000, 0xFFFF or 0x1D0F) as crc parameter. + * Provide the previous crc value returned for each successive call corresponding to + * a new chunk of data in a given set. + * buf is a pointer to the buffer holding the data, and len the length of the data in + * the buffer. + * Returns the updated crc if buf is not null, or the old value when buff is null. + */ +uint16_t crc_ccitt(uint16_t crc, uint8_t* buf, int len) +{ + int i = 0; + if (buf == NULL) { + return crc; + } + for (i = 0; i < len; i++) { + crc = (crc << 8) ^ crc_ccitt_table[ ((crc >> 8) ^ (uint16_t)buf[i]) & 0x00FF ]; + } + return crc; +} + + + + +/***************************************************************************** */ +/* The following program got used to generate the above table : */ +#if 0 +#include +#include + +#define CRC_POLY_CCITT 0x1021 +int main(void) +{ + int i = 0; + + printf("static const uint16_t crc_ccitt_table[256] = {"); + + for (i = 0; i < 256; i++) { + int j = 0; + uint16_t crc = 0; + uint16_t c = i << 8; + + for (j = 0; j < 8; j++) { + if ((crc ^ c) & 0x8000) { + crc = (crc << 1) ^ CRC_POLY_CCITT; + } else { + crc = crc << 1; + } + c = c << 1; + } + + if (i % 16 == 0) { + printf("\n\t"); + } + printf("0x%04x, ", crc); + } + printf("\n};\n"); + + return 0; +} +#endif +