mbed unsupported / SDFileSystem

SDFileSystem, included for backwards compatibility.

SDFileSystem.cpp@0:6afe57e15f1a, 2012-05-08 (annotated)

Committer:
root@mbed.org
Date:
Tue May 08 15:20:54 2012 +0100
Revision:
0:6afe57e15f1a
Initial commit

Who changed what in which revision?

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root@mbed.org 0:6afe57e15f1a 1 /* mbed Microcontroller Library - SDFileSystem
root@mbed.org 0:6afe57e15f1a 2 * Copyright (c) 2008-2009, sford
root@mbed.org 0:6afe57e15f1a 3 *
root@mbed.org 0:6afe57e15f1a 4 * Introduction
root@mbed.org 0:6afe57e15f1a 5 * ------------
root@mbed.org 0:6afe57e15f1a 6 * SD and MMC cards support a number of interfaces, but common to them all
root@mbed.org 0:6afe57e15f1a 7 * is one based on SPI. This is the one I'm implmenting because it means
root@mbed.org 0:6afe57e15f1a 8 * it is much more portable even though not so performant, and we already
root@mbed.org 0:6afe57e15f1a 9 * have the mbed SPI Interface!
root@mbed.org 0:6afe57e15f1a 10 *
root@mbed.org 0:6afe57e15f1a 11 * The main reference I'm using is Chapter 7, "SPI Mode" of:
root@mbed.org 0:6afe57e15f1a 12 * http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
root@mbed.org 0:6afe57e15f1a 13 *
root@mbed.org 0:6afe57e15f1a 14 * SPI Startup
root@mbed.org 0:6afe57e15f1a 15 * -----------
root@mbed.org 0:6afe57e15f1a 16 * The SD card powers up in SD mode. The SPI interface mode is selected by
root@mbed.org 0:6afe57e15f1a 17 * asserting CS low and sending the reset command (CMD0). The card will
root@mbed.org 0:6afe57e15f1a 18 * respond with a (R1) response.
root@mbed.org 0:6afe57e15f1a 19 *
root@mbed.org 0:6afe57e15f1a 20 * CMD8 is optionally sent to determine the voltage range supported, and
root@mbed.org 0:6afe57e15f1a 21 * indirectly determine whether it is a version 1.x SD/non-SD card or
root@mbed.org 0:6afe57e15f1a 22 * version 2.x. I'll just ignore this for now.
root@mbed.org 0:6afe57e15f1a 23 *
root@mbed.org 0:6afe57e15f1a 24 * ACMD41 is repeatedly issued to initialise the card, until "in idle"
root@mbed.org 0:6afe57e15f1a 25 * (bit 0) of the R1 response goes to '0', indicating it is initialised.
root@mbed.org 0:6afe57e15f1a 26 *
root@mbed.org 0:6afe57e15f1a 27 * You should also indicate whether the host supports High Capicity cards,
root@mbed.org 0:6afe57e15f1a 28 * and check whether the card is high capacity - i'll also ignore this
root@mbed.org 0:6afe57e15f1a 29 *
root@mbed.org 0:6afe57e15f1a 30 * SPI Protocol
root@mbed.org 0:6afe57e15f1a 31 * ------------
root@mbed.org 0:6afe57e15f1a 32 * The SD SPI protocol is based on transactions made up of 8-bit words, with
root@mbed.org 0:6afe57e15f1a 33 * the host starting every bus transaction by asserting the CS signal low. The
root@mbed.org 0:6afe57e15f1a 34 * card always responds to commands, data blocks and errors.
root@mbed.org 0:6afe57e15f1a 35 *
root@mbed.org 0:6afe57e15f1a 36 * The protocol supports a CRC, but by default it is off (except for the
root@mbed.org 0:6afe57e15f1a 37 * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
root@mbed.org 0:6afe57e15f1a 38 * I'll leave the CRC off I think!
root@mbed.org 0:6afe57e15f1a 39 *
root@mbed.org 0:6afe57e15f1a 40 * Standard capacity cards have variable data block sizes, whereas High
root@mbed.org 0:6afe57e15f1a 41 * Capacity cards fix the size of data block to 512 bytes. I'll therefore
root@mbed.org 0:6afe57e15f1a 42 * just always use the Standard Capacity cards with a block size of 512 bytes.
root@mbed.org 0:6afe57e15f1a 43 * This is set with CMD16.
root@mbed.org 0:6afe57e15f1a 44 *
root@mbed.org 0:6afe57e15f1a 45 * You can read and write single blocks (CMD17, CMD25) or multiple blocks
root@mbed.org 0:6afe57e15f1a 46 * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
root@mbed.org 0:6afe57e15f1a 47 * the card gets a read command, it responds with a response token, and then
root@mbed.org 0:6afe57e15f1a 48 * a data token or an error.
root@mbed.org 0:6afe57e15f1a 49 *
root@mbed.org 0:6afe57e15f1a 50 * SPI Command Format
root@mbed.org 0:6afe57e15f1a 51 * ------------------
root@mbed.org 0:6afe57e15f1a 52 * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
root@mbed.org 0:6afe57e15f1a 53 *
root@mbed.org 0:6afe57e15f1a 54 * +---------------+------------+------------+-----------+----------+--------------+
root@mbed.org 0:6afe57e15f1a 55 * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
root@mbed.org 0:6afe57e15f1a 56 * +---------------+------------+------------+-----------+----------+--------------+
root@mbed.org 0:6afe57e15f1a 57 *
root@mbed.org 0:6afe57e15f1a 58 * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
root@mbed.org 0:6afe57e15f1a 59 *
root@mbed.org 0:6afe57e15f1a 60 * All Application Specific commands shall be preceded with APP_CMD (CMD55).
root@mbed.org 0:6afe57e15f1a 61 *
root@mbed.org 0:6afe57e15f1a 62 * SPI Response Format
root@mbed.org 0:6afe57e15f1a 63 * -------------------
root@mbed.org 0:6afe57e15f1a 64 * The main response format (R1) is a status byte (normally zero). Key flags:
root@mbed.org 0:6afe57e15f1a 65 * idle - 1 if the card is in an idle state/initialising
root@mbed.org 0:6afe57e15f1a 66 * cmd - 1 if an illegal command code was detected
root@mbed.org 0:6afe57e15f1a 67 *
root@mbed.org 0:6afe57e15f1a 68 * +-------------------------------------------------+
root@mbed.org 0:6afe57e15f1a 69 * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
root@mbed.org 0:6afe57e15f1a 70 * +-------------------------------------------------+
root@mbed.org 0:6afe57e15f1a 71 *
root@mbed.org 0:6afe57e15f1a 72 * R1b is the same, except it is followed by a busy signal (zeros) until
root@mbed.org 0:6afe57e15f1a 73 * the first non-zero byte when it is ready again.
root@mbed.org 0:6afe57e15f1a 74 *
root@mbed.org 0:6afe57e15f1a 75 * Data Response Token
root@mbed.org 0:6afe57e15f1a 76 * -------------------
root@mbed.org 0:6afe57e15f1a 77 * Every data block written to the card is acknowledged by a byte
root@mbed.org 0:6afe57e15f1a 78 * response token
root@mbed.org 0:6afe57e15f1a 79 *
root@mbed.org 0:6afe57e15f1a 80 * +----------------------+
root@mbed.org 0:6afe57e15f1a 81 * | xxx | 0 | status | 1 |
root@mbed.org 0:6afe57e15f1a 82 * +----------------------+
root@mbed.org 0:6afe57e15f1a 83 * 010 - OK!
root@mbed.org 0:6afe57e15f1a 84 * 101 - CRC Error
root@mbed.org 0:6afe57e15f1a 85 * 110 - Write Error
root@mbed.org 0:6afe57e15f1a 86 *
root@mbed.org 0:6afe57e15f1a 87 * Single Block Read and Write
root@mbed.org 0:6afe57e15f1a 88 * ---------------------------
root@mbed.org 0:6afe57e15f1a 89 *
root@mbed.org 0:6afe57e15f1a 90 * Block transfers have a byte header, followed by the data, followed
root@mbed.org 0:6afe57e15f1a 91 * by a 16-bit CRC. In our case, the data will always be 512 bytes.
root@mbed.org 0:6afe57e15f1a 92 *
root@mbed.org 0:6afe57e15f1a 93 * +------+---------+---------+- - - -+---------+-----------+----------+
root@mbed.org 0:6afe57e15f1a 94 * | 0xFE | data[0] | data[1] | | data[n] | crc[15:8] | crc[7:0] |
root@mbed.org 0:6afe57e15f1a 95 * +------+---------+---------+- - - -+---------+-----------+----------+
root@mbed.org 0:6afe57e15f1a 96 */
root@mbed.org 0:6afe57e15f1a 97
root@mbed.org 0:6afe57e15f1a 98 #include "SDFileSystem.h"
root@mbed.org 0:6afe57e15f1a 99
root@mbed.org 0:6afe57e15f1a 100 #define SD_COMMAND_TIMEOUT 5000
root@mbed.org 0:6afe57e15f1a 101
root@mbed.org 0:6afe57e15f1a 102 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
root@mbed.org 0:6afe57e15f1a 103 FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
root@mbed.org 0:6afe57e15f1a 104 _cs = 1;
root@mbed.org 0:6afe57e15f1a 105 }
root@mbed.org 0:6afe57e15f1a 106
root@mbed.org 0:6afe57e15f1a 107 int SDFileSystem::disk_initialize() {
root@mbed.org 0:6afe57e15f1a 108
root@mbed.org 0:6afe57e15f1a 109 _spi.frequency(100000); // Set to 100kHz for initialisation
root@mbed.org 0:6afe57e15f1a 110
root@mbed.org 0:6afe57e15f1a 111 // Initialise the card by clocking it a bit (cs = 1)
root@mbed.org 0:6afe57e15f1a 112 for(int i=0; i<16; i++) {
root@mbed.org 0:6afe57e15f1a 113 _spi.write(0xFF);
root@mbed.org 0:6afe57e15f1a 114 }
root@mbed.org 0:6afe57e15f1a 115
root@mbed.org 0:6afe57e15f1a 116 // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
root@mbed.org 0:6afe57e15f1a 117 if(_cmd(0, 0) != 0x01) {
root@mbed.org 0:6afe57e15f1a 118 fprintf(stderr, "Not in idle state\n");
root@mbed.org 0:6afe57e15f1a 119 return 1;
root@mbed.org 0:6afe57e15f1a 120 }
root@mbed.org 0:6afe57e15f1a 121
root@mbed.org 0:6afe57e15f1a 122 // ACMD41 to give host capacity support (repeat until not busy)
root@mbed.org 0:6afe57e15f1a 123 // ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
root@mbed.org 0:6afe57e15f1a 124 for(int i=0;; i++) {
root@mbed.org 0:6afe57e15f1a 125 _cmd(55, 0);
root@mbed.org 0:6afe57e15f1a 126 int response = _cmd(41, 0);
root@mbed.org 0:6afe57e15f1a 127 if(response == 0) {
root@mbed.org 0:6afe57e15f1a 128 break;
root@mbed.org 0:6afe57e15f1a 129 } else if(i > SD_COMMAND_TIMEOUT) {
root@mbed.org 0:6afe57e15f1a 130 fprintf(stderr, "Timeout waiting for card\n");
root@mbed.org 0:6afe57e15f1a 131 return 1;
root@mbed.org 0:6afe57e15f1a 132 }
root@mbed.org 0:6afe57e15f1a 133 }
root@mbed.org 0:6afe57e15f1a 134
root@mbed.org 0:6afe57e15f1a 135 _sectors = _sd_sectors();
root@mbed.org 0:6afe57e15f1a 136
root@mbed.org 0:6afe57e15f1a 137 // Set block length to 512 (CMD16)
root@mbed.org 0:6afe57e15f1a 138 if(_cmd(16, 512) != 0) {
root@mbed.org 0:6afe57e15f1a 139 fprintf(stderr, "Set block timeout\n");
root@mbed.org 0:6afe57e15f1a 140 return 1;
root@mbed.org 0:6afe57e15f1a 141 }
root@mbed.org 0:6afe57e15f1a 142
root@mbed.org 0:6afe57e15f1a 143 _spi.frequency(1000000); // Set to 1MHz for data transfer
root@mbed.org 0:6afe57e15f1a 144 return 0;
root@mbed.org 0:6afe57e15f1a 145 }
root@mbed.org 0:6afe57e15f1a 146
root@mbed.org 0:6afe57e15f1a 147 int SDFileSystem::disk_write(const char *buffer, int block_number) {
root@mbed.org 0:6afe57e15f1a 148 // set write address for single block (CMD24)
root@mbed.org 0:6afe57e15f1a 149 if(_cmd(24, block_number * 512) != 0) {
root@mbed.org 0:6afe57e15f1a 150 return 1;
root@mbed.org 0:6afe57e15f1a 151 }
root@mbed.org 0:6afe57e15f1a 152
root@mbed.org 0:6afe57e15f1a 153 // send the data block
root@mbed.org 0:6afe57e15f1a 154 _write(buffer, 512);
root@mbed.org 0:6afe57e15f1a 155 return 0;
root@mbed.org 0:6afe57e15f1a 156 }
root@mbed.org 0:6afe57e15f1a 157
root@mbed.org 0:6afe57e15f1a 158 int SDFileSystem::disk_read(char *buffer, int block_number) {
root@mbed.org 0:6afe57e15f1a 159 // set read address for single block (CMD17)
root@mbed.org 0:6afe57e15f1a 160 if(_cmd(17, block_number * 512) != 0) {
root@mbed.org 0:6afe57e15f1a 161 return 1;
root@mbed.org 0:6afe57e15f1a 162 }
root@mbed.org 0:6afe57e15f1a 163
root@mbed.org 0:6afe57e15f1a 164 // receive the data
root@mbed.org 0:6afe57e15f1a 165 _read(buffer, 512);
root@mbed.org 0:6afe57e15f1a 166 return 0;
root@mbed.org 0:6afe57e15f1a 167 }
root@mbed.org 0:6afe57e15f1a 168
root@mbed.org 0:6afe57e15f1a 169 int SDFileSystem::disk_status() { return 0; }
root@mbed.org 0:6afe57e15f1a 170 int SDFileSystem::disk_sync() { return 0; }
root@mbed.org 0:6afe57e15f1a 171 int SDFileSystem::disk_sectors() { return _sectors; }
root@mbed.org 0:6afe57e15f1a 172
root@mbed.org 0:6afe57e15f1a 173 // PRIVATE FUNCTIONS
root@mbed.org 0:6afe57e15f1a 174
root@mbed.org 0:6afe57e15f1a 175 int SDFileSystem::_cmd(int cmd, int arg) {
root@mbed.org 0:6afe57e15f1a 176 _cs = 0;
root@mbed.org 0:6afe57e15f1a 177
root@mbed.org 0:6afe57e15f1a 178 // send a command
root@mbed.org 0:6afe57e15f1a 179 _spi.write(0x40 | cmd);
root@mbed.org 0:6afe57e15f1a 180 _spi.write(arg >> 24);
root@mbed.org 0:6afe57e15f1a 181 _spi.write(arg >> 16);
root@mbed.org 0:6afe57e15f1a 182 _spi.write(arg >> 8);
root@mbed.org 0:6afe57e15f1a 183 _spi.write(arg >> 0);
root@mbed.org 0:6afe57e15f1a 184 _spi.write(0x95);
root@mbed.org 0:6afe57e15f1a 185
root@mbed.org 0:6afe57e15f1a 186 // wait for the repsonse (response[7] == 0)
root@mbed.org 0:6afe57e15f1a 187 for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
root@mbed.org 0:6afe57e15f1a 188 int response = _spi.write(0xFF);
root@mbed.org 0:6afe57e15f1a 189 if(!(response & 0x80)) {
root@mbed.org 0:6afe57e15f1a 190 _cs = 1;
root@mbed.org 0:6afe57e15f1a 191 return response;
root@mbed.org 0:6afe57e15f1a 192 }
root@mbed.org 0:6afe57e15f1a 193 }
root@mbed.org 0:6afe57e15f1a 194 _cs = 1;
root@mbed.org 0:6afe57e15f1a 195 return -1; // timeout
root@mbed.org 0:6afe57e15f1a 196 }
root@mbed.org 0:6afe57e15f1a 197
root@mbed.org 0:6afe57e15f1a 198 int SDFileSystem::_read(char *buffer, int length) {
root@mbed.org 0:6afe57e15f1a 199 _cs = 0;
root@mbed.org 0:6afe57e15f1a 200
root@mbed.org 0:6afe57e15f1a 201 // read until start byte (0xFF)
root@mbed.org 0:6afe57e15f1a 202 while(_spi.write(0xFF) != 0xFE);
root@mbed.org 0:6afe57e15f1a 203
root@mbed.org 0:6afe57e15f1a 204 // read data
root@mbed.org 0:6afe57e15f1a 205 for(int i=0; i<length; i++) {
root@mbed.org 0:6afe57e15f1a 206 buffer[i] = _spi.write(0xFF);
root@mbed.org 0:6afe57e15f1a 207 }
root@mbed.org 0:6afe57e15f1a 208 _spi.write(0xFF); // checksum
root@mbed.org 0:6afe57e15f1a 209 _spi.write(0xFF);
root@mbed.org 0:6afe57e15f1a 210
root@mbed.org 0:6afe57e15f1a 211 _cs = 1;
root@mbed.org 0:6afe57e15f1a 212 return 0;
root@mbed.org 0:6afe57e15f1a 213 }
root@mbed.org 0:6afe57e15f1a 214
root@mbed.org 0:6afe57e15f1a 215 int SDFileSystem::_write(const char *buffer, int length) {
root@mbed.org 0:6afe57e15f1a 216 _cs = 0;
root@mbed.org 0:6afe57e15f1a 217
root@mbed.org 0:6afe57e15f1a 218 // indicate start of block
root@mbed.org 0:6afe57e15f1a 219 _spi.write(0xFE);
root@mbed.org 0:6afe57e15f1a 220
root@mbed.org 0:6afe57e15f1a 221 // write the data
root@mbed.org 0:6afe57e15f1a 222 for(int i=0; i<length; i++) {
root@mbed.org 0:6afe57e15f1a 223 _spi.write(buffer[i]);
root@mbed.org 0:6afe57e15f1a 224 }
root@mbed.org 0:6afe57e15f1a 225
root@mbed.org 0:6afe57e15f1a 226 // write the checksum
root@mbed.org 0:6afe57e15f1a 227 _spi.write(0xFF);
root@mbed.org 0:6afe57e15f1a 228 _spi.write(0xFF);
root@mbed.org 0:6afe57e15f1a 229
root@mbed.org 0:6afe57e15f1a 230 // check the repsonse token
root@mbed.org 0:6afe57e15f1a 231 if((_spi.write(0xFF) & 0x1F) != 0x05) {
root@mbed.org 0:6afe57e15f1a 232 _cs = 1;
root@mbed.org 0:6afe57e15f1a 233 return 1;
root@mbed.org 0:6afe57e15f1a 234 }
root@mbed.org 0:6afe57e15f1a 235
root@mbed.org 0:6afe57e15f1a 236 // wait for write to finish
root@mbed.org 0:6afe57e15f1a 237 while(_spi.write(0xFF) == 0);
root@mbed.org 0:6afe57e15f1a 238
root@mbed.org 0:6afe57e15f1a 239 _cs = 1;
root@mbed.org 0:6afe57e15f1a 240 return 0;
root@mbed.org 0:6afe57e15f1a 241 }
root@mbed.org 0:6afe57e15f1a 242
root@mbed.org 0:6afe57e15f1a 243 static int ext_bits(char *data, int msb, int lsb) {
root@mbed.org 0:6afe57e15f1a 244 int bits = 0;
root@mbed.org 0:6afe57e15f1a 245 int size = 1 + msb - lsb;
root@mbed.org 0:6afe57e15f1a 246 for(int i=0; i<size; i++) {
root@mbed.org 0:6afe57e15f1a 247 int position = lsb + i;
root@mbed.org 0:6afe57e15f1a 248 int byte = 15 - (position >> 3);
root@mbed.org 0:6afe57e15f1a 249 int bit = position & 0x7;
root@mbed.org 0:6afe57e15f1a 250 int value = (data[byte] >> bit) & 1;
root@mbed.org 0:6afe57e15f1a 251 bits |= value << i;
root@mbed.org 0:6afe57e15f1a 252 }
root@mbed.org 0:6afe57e15f1a 253 return bits;
root@mbed.org 0:6afe57e15f1a 254 }
root@mbed.org 0:6afe57e15f1a 255
root@mbed.org 0:6afe57e15f1a 256 int SDFileSystem::_sd_sectors() {
root@mbed.org 0:6afe57e15f1a 257
root@mbed.org 0:6afe57e15f1a 258 // CMD9, Response R2 (R1 byte + 16-byte block read)
root@mbed.org 0:6afe57e15f1a 259 if(_cmd(9, 0) != 0) {
root@mbed.org 0:6afe57e15f1a 260 fprintf(stderr, "Didn't get a response from the disk\n");
root@mbed.org 0:6afe57e15f1a 261 return 0;
root@mbed.org 0:6afe57e15f1a 262 }
root@mbed.org 0:6afe57e15f1a 263
root@mbed.org 0:6afe57e15f1a 264 char csd[16];
root@mbed.org 0:6afe57e15f1a 265 if(_read(csd, 16) != 0) {
root@mbed.org 0:6afe57e15f1a 266 fprintf(stderr, "Couldn't read csd response from disk\n");
root@mbed.org 0:6afe57e15f1a 267 return 0;
root@mbed.org 0:6afe57e15f1a 268 }
root@mbed.org 0:6afe57e15f1a 269
root@mbed.org 0:6afe57e15f1a 270 // csd_structure : csd[127:126]
root@mbed.org 0:6afe57e15f1a 271 // c_size : csd[73:62]
root@mbed.org 0:6afe57e15f1a 272 // c_size_mult : csd[49:47]
root@mbed.org 0:6afe57e15f1a 273 // read_bl_len : csd[83:80]
root@mbed.org 0:6afe57e15f1a 274
root@mbed.org 0:6afe57e15f1a 275 int csd_structure = ext_bits(csd, 127, 126);
root@mbed.org 0:6afe57e15f1a 276 int c_size = ext_bits(csd, 73, 62);
root@mbed.org 0:6afe57e15f1a 277 int c_size_mult = ext_bits(csd, 49, 47);
root@mbed.org 0:6afe57e15f1a 278 int read_bl_len = ext_bits(csd, 83, 80);
root@mbed.org 0:6afe57e15f1a 279
root@mbed.org 0:6afe57e15f1a 280 if(csd_structure != 0) {
root@mbed.org 0:6afe57e15f1a 281 fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
root@mbed.org 0:6afe57e15f1a 282 return 0;
root@mbed.org 0:6afe57e15f1a 283 }
root@mbed.org 0:6afe57e15f1a 284
root@mbed.org 0:6afe57e15f1a 285 int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
root@mbed.org 0:6afe57e15f1a 286 int block_size = 1 << read_bl_len;
root@mbed.org 0:6afe57e15f1a 287
root@mbed.org 0:6afe57e15f1a 288 if(block_size != 512) {
root@mbed.org 0:6afe57e15f1a 289 fprintf(stderr, "This disk tastes funny! I only like 512-byte blocks");
root@mbed.org 0:6afe57e15f1a 290 return 0;
root@mbed.org 0:6afe57e15f1a 291 }
root@mbed.org 0:6afe57e15f1a 292
root@mbed.org 0:6afe57e15f1a 293 return blocks;
root@mbed.org 0:6afe57e15f1a 294 }