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125 lines
3.3 KiB
C
125 lines
3.3 KiB
C
/*
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io_sd_common.c
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By chishm (Michael Chisholm)
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Common SD card routines
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SD routines partially based on sd.s by Romman
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Copyright (c) 2006 Michael "Chishm" Chisholm
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Redistribution and use in source and binary forms, with or without modification,
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are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation and/or
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other materials provided with the distribution.
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3. The name of the author may not be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
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AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "io_sd_common.h"
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/*
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Improved CRC7 function provided by cory1492
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Calculates the CRC of an SD command, and includes the end bit in the byte
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*/
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u8 _SD_CRC7(u8* data, int cnt) {
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int i, a;
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u8 crc, temp;
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crc = 0;
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for (a = 0; a < cnt; a++)
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{
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temp = data[a];
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for (i = 0; i < 8; i++)
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{
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crc <<= 1;
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if ((temp & 0x80) ^ (crc & 0x80)) crc ^= 0x09;
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temp <<= 1;
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}
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}
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crc = (crc << 1) | 1;
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return(crc);
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}
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/*
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Calculates the CRC16 for a sector of data. Calculates it
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as 4 separate lots, merged into one buffer. This is used
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for 4 SD data lines, not for 1 data line alone.
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*/
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void _SD_CRC16 (u8* buff, int buffLength, u8* crc16buff) {
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u32 a, b, c, d;
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int count;
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u32 bitPattern = 0x80808080; // r7
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u32 crcConst = 0x1021; // r8
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u32 dataByte = 0; // r2
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a = 0; // r3
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b = 0; // r4
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c = 0; // r5
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d = 0; // r6
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buffLength = buffLength * 8;
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do {
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if (bitPattern & 0x80) dataByte = *buff++;
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a = a << 1;
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if ( a & 0x10000) a ^= crcConst;
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if (dataByte & (bitPattern >> 24)) a ^= crcConst;
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b = b << 1;
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if (b & 0x10000) b ^= crcConst;
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if (dataByte & (bitPattern >> 25)) b ^= crcConst;
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c = c << 1;
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if (c & 0x10000) c ^= crcConst;
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if (dataByte & (bitPattern >> 26)) c ^= crcConst;
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d = d << 1;
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if (d & 0x10000) d ^= crcConst;
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if (dataByte & (bitPattern >> 27)) d ^= crcConst;
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bitPattern = (bitPattern >> 4) | (bitPattern << 28);
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} while (buffLength-=4);
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count = 16; // r8
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do {
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bitPattern = bitPattern << 4;
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if (a & 0x8000) bitPattern |= 8;
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if (b & 0x8000) bitPattern |= 4;
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if (c & 0x8000) bitPattern |= 2;
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if (d & 0x8000) bitPattern |= 1;
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a = a << 1;
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b = b << 1;
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c = c << 1;
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d = d << 1;
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count--;
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if (!(count & 0x01)) {
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*crc16buff++ = (u8)(bitPattern & 0xff);
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}
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} while (count != 0);
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return;
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}
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