SDFileSystem.cpp

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2006-2012 ARM Limited
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy
00005  * of this software and associated documentation files (the "Software"), to deal
00006  * in the Software without restriction, including without limitation the rights
00007  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00008  * copies of the Software, and to permit persons to whom the Software is
00009  * furnished to do so, subject to the following conditions:
00010  *
00011  * The above copyright notice and this permission notice shall be included in
00012  * all copies or substantial portions of the Software.
00013  *
00014  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00015  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00016  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00017  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00018  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00019  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
00020  * SOFTWARE.
00021  */
00022 
00023 /* Introduction
00024  * ------------
00025  * SD and MMC cards support a number of interfaces, but common to them all
00026  * is one based on SPI. This is the one I'm implmenting because it means
00027  * it is much more portable even though not so performant, and we already
00028  * have the mbed SPI Interface!
00029  *
00030  * The main reference I'm using is Chapter 7, "SPI Mode" of:
00031  *  http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
00032  *
00033  * SPI Startup
00034  * -----------
00035  * The SD card powers up in SD mode. The SPI interface mode is selected by
00036  * asserting CS low and sending the reset command (CMD0). The card will
00037  * respond with a (R1) response.
00038  *
00039  * CMD8 is optionally sent to determine the voltage range supported, and
00040  * indirectly determine whether it is a version 1.x SD/non-SD card or
00041  * version 2.x. I'll just ignore this for now.
00042  *
00043  * ACMD41 is repeatedly issued to initialise the card, until "in idle"
00044  * (bit 0) of the R1 response goes to '0', indicating it is initialised.
00045  *
00046  * You should also indicate whether the host supports High Capicity cards,
00047  * and check whether the card is high capacity - i'll also ignore this
00048  *
00049  * SPI Protocol
00050  * ------------
00051  * The SD SPI protocol is based on transactions made up of 8-bit words, with
00052  * the host starting every bus transaction by asserting the CS signal low. The
00053  * card always responds to commands, data blocks and errors.
00054  *
00055  * The protocol supports a CRC, but by default it is off (except for the
00056  * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
00057  * I'll leave the CRC off I think!
00058  *
00059  * Standard capacity cards have variable data block sizes, whereas High
00060  * Capacity cards fix the size of data block to 512 bytes. I'll therefore
00061  * just always use the Standard Capacity cards with a block size of 512 bytes.
00062  * This is set with CMD16.
00063  *
00064  * You can read and write single blocks (CMD17, CMD25) or multiple blocks
00065  * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
00066  * the card gets a read command, it responds with a response token, and then
00067  * a data token or an error.
00068  *
00069  * SPI Command Format
00070  * ------------------
00071  * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
00072  *
00073  * +---------------+------------+------------+-----------+----------+--------------+
00074  * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
00075  * +---------------+------------+------------+-----------+----------+--------------+
00076  *
00077  * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
00078  *
00079  * All Application Specific commands shall be preceded with APP_CMD (CMD55).
00080  *
00081  * SPI Response Format
00082  * -------------------
00083  * The main response format (R1) is a status byte (normally zero). Key flags:
00084  *  idle - 1 if the card is in an idle state/initialising
00085  *  cmd  - 1 if an illegal command code was detected
00086  *
00087  *    +-------------------------------------------------+
00088  * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
00089  *    +-------------------------------------------------+
00090  *
00091  * R1b is the same, except it is followed by a busy signal (zeros) until
00092  * the first non-zero byte when it is ready again.
00093  *
00094  * Data Response Token
00095  * -------------------
00096  * Every data block written to the card is acknowledged by a byte
00097  * response token
00098  *
00099  * +----------------------+
00100  * | xxx | 0 | status | 1 |
00101  * +----------------------+
00102  *              010 - OK!
00103  *              101 - CRC Error
00104  *              110 - Write Error
00105  *
00106  * Single Block Read and Write
00107  * ---------------------------
00108  *
00109  * Block transfers have a byte header, followed by the data, followed
00110  * by a 16-bit CRC. In our case, the data will always be 512 bytes.
00111  *
00112  * +------+---------+---------+- -  - -+---------+-----------+----------+
00113  * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
00114  * +------+---------+---------+- -  - -+---------+-----------+----------+
00115  */
00116 #include "SDFileSystem.h"
00117 #include "mbed_debug.h"
00118 
00119 #define SD_COMMAND_TIMEOUT 5000
00120 
00121 #define SD_DBG             0
00122 
00123 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
00124     FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
00125     _cs = 1;
00126 }
00127 
00128 #define R1_IDLE_STATE           (1 << 0)
00129 #define R1_ERASE_RESET          (1 << 1)
00130 #define R1_ILLEGAL_COMMAND      (1 << 2)
00131 #define R1_COM_CRC_ERROR        (1 << 3)
00132 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00133 #define R1_ADDRESS_ERROR        (1 << 5)
00134 #define R1_PARAMETER_ERROR      (1 << 6)
00135 
00136 // Types
00137 #define SDCARD_FAIL 0 //!< v1.x Standard Capacity
00138 #define SDCARD_V1   1 //!< v2.x Standard Capacity
00139 #define SDCARD_V2   2 //!< v2.x High Capacity
00140 #define SDCARD_V2HC 3 //!< Not recognised as an SD Card
00141 
00142 int SDFileSystem::initialise_card() {
00143     // Set to 100kHz for initialisation, and clock card with cs = 1
00144     _spi.frequency(100000);
00145     _cs = 1;
00146     for (int i = 0; i < 16; i++) {
00147         _spi.write(0xFF);
00148     }
00149     
00150     // Make three attempts at getting the card in IDLE STATE
00151     int r;
00152     for (int attempt = 0; attempt < 3; attempt++) {
00153         // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00154         r = _cmd(0, 0);
00155         if (r == R1_IDLE_STATE) {
00156             break;
00157         } else {
00158             wait(0.1);
00159         }
00160     }
00161     if (r != R1_IDLE_STATE) {
00162         debug("No disk, or could not put SD card in to SPI idle state\n");
00163         return SDCARD_FAIL;
00164     }
00165     
00166     // send CMD8 to determine whther it is ver 2.x
00167     r = _cmd8();
00168     if (r == R1_IDLE_STATE) {
00169         return initialise_card_v2();
00170     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00171         return initialise_card_v1();
00172     } else {
00173         debug("Not in idle state after sending CMD8 (not an SD card?)\n");
00174         return SDCARD_FAIL;
00175     }
00176 }
00177 
00178 int SDFileSystem::initialise_card_v1() {
00179     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00180         _cmd(55, 0);
00181         if (_cmd(41, 0) == 0) {
00182             cdv = 512;
00183             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00184             return SDCARD_V1;
00185         }
00186     }
00187     
00188     debug("Timeout waiting for v1.x card\n");
00189     return SDCARD_FAIL;
00190 }
00191 
00192 int SDFileSystem::initialise_card_v2() {
00193     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00194         wait_ms(50);
00195         _cmd58();
00196         _cmd(55, 0);
00197         if (_cmd(41, 0x40000000) == 0) {
00198             _cmd58();
00199             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00200             cdv = 1;
00201             return SDCARD_V2;
00202         }
00203     }
00204     
00205     debug("Timeout waiting for v2.x card\n");
00206     return SDCARD_FAIL;
00207 }
00208 
00209 int SDFileSystem::disk_initialize() {
00210     int i = initialise_card();
00211     debug_if(SD_DBG, "init card = %d\n", i);
00212     _sectors = _sd_sectors();
00213     
00214     // Set block length to 512 (CMD16)
00215     if (_cmd(16, 512) != 0) {
00216         debug("Set 512-byte block timed out\n");
00217         return 1;
00218     }
00219     
00220     _spi.frequency(1000000); // Set to 1MHz for data transfer
00221     return 0;
00222 }
00223 
00224 int SDFileSystem::disk_write(const uint8_t *buffer, uint64_t block_number) {
00225     // set write address for single block (CMD24)
00226     if (_cmd(24, block_number * cdv) != 0) {
00227         return 1;
00228     }
00229     
00230     // send the data block
00231     _write(buffer, 512);
00232     return 0;
00233 }
00234 
00235 int SDFileSystem::disk_read(uint8_t *buffer, uint64_t block_number) {
00236     // set read address for single block (CMD17)
00237     if (_cmd(17, block_number * cdv) != 0) {
00238         return 1;
00239     }
00240     
00241     // receive the data
00242     _read(buffer, 512);
00243     return 0;
00244 }
00245 
00246 int SDFileSystem::disk_status() { return 0; }
00247 int SDFileSystem::disk_sync() { return 0; }
00248 uint64_t SDFileSystem::disk_sectors() { return _sectors; }
00249 
00250 
00251 // PRIVATE FUNCTIONS
00252 int SDFileSystem::_cmd(int cmd, int arg) {
00253     _cs = 0;
00254     
00255     // send a command
00256     _spi.write(0x40 | cmd);
00257     _spi.write(arg >> 24);
00258     _spi.write(arg >> 16);
00259     _spi.write(arg >> 8);
00260     _spi.write(arg >> 0);
00261     _spi.write(0x95);
00262     
00263     // wait for the repsonse (response[7] == 0)
00264     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00265         int response = _spi.write(0xFF);
00266         if (!(response & 0x80)) {
00267             _cs = 1;
00268             _spi.write(0xFF);
00269             return response;
00270         }
00271     }
00272     _cs = 1;
00273     _spi.write(0xFF);
00274     return -1; // timeout
00275 }
00276 int SDFileSystem::_cmdx(int cmd, int arg) {
00277     _cs = 0;
00278     
00279     // send a command
00280     _spi.write(0x40 | cmd);
00281     _spi.write(arg >> 24);
00282     _spi.write(arg >> 16);
00283     _spi.write(arg >> 8);
00284     _spi.write(arg >> 0);
00285     _spi.write(0x95);
00286     
00287     // wait for the repsonse (response[7] == 0)
00288     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00289         int response = _spi.write(0xFF);
00290         if (!(response & 0x80)) {
00291             return response;
00292         }
00293     }
00294     _cs = 1;
00295     _spi.write(0xFF);
00296     return -1; // timeout
00297 }
00298 
00299 
00300 int SDFileSystem::_cmd58() {
00301     _cs = 0;
00302     int arg = 0;
00303     
00304     // send a command
00305     _spi.write(0x40 | 58);
00306     _spi.write(arg >> 24);
00307     _spi.write(arg >> 16);
00308     _spi.write(arg >> 8);
00309     _spi.write(arg >> 0);
00310     _spi.write(0x95);
00311     
00312     // wait for the repsonse (response[7] == 0)
00313     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00314         int response = _spi.write(0xFF);
00315         if (!(response & 0x80)) {
00316             int ocr = _spi.write(0xFF) << 24;
00317             ocr |= _spi.write(0xFF) << 16;
00318             ocr |= _spi.write(0xFF) << 8;
00319             ocr |= _spi.write(0xFF) << 0;
00320             _cs = 1;
00321             _spi.write(0xFF);
00322             return response;
00323         }
00324     }
00325     _cs = 1;
00326     _spi.write(0xFF);
00327     return -1; // timeout
00328 }
00329 
00330 int SDFileSystem::_cmd8() {
00331     _cs = 0;
00332     
00333     // send a command
00334     _spi.write(0x40 | 8); // CMD8
00335     _spi.write(0x00);     // reserved
00336     _spi.write(0x00);     // reserved
00337     _spi.write(0x01);     // 3.3v
00338     _spi.write(0xAA);     // check pattern
00339     _spi.write(0x87);     // crc
00340     
00341     // wait for the repsonse (response[7] == 0)
00342     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00343         char response[5];
00344         response[0] = _spi.write(0xFF);
00345         if (!(response[0] & 0x80)) {
00346             for (int j = 1; j < 5; j++) {
00347                 response[i] = _spi.write(0xFF);
00348             }
00349             _cs = 1;
00350             _spi.write(0xFF);
00351             return response[0];
00352         }
00353     }
00354     _cs = 1;
00355     _spi.write(0xFF);
00356     return -1; // timeout
00357 }
00358 
00359 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00360     _cs = 0;
00361     
00362     // read until start byte (0xFF)
00363     while (_spi.write(0xFF) != 0xFE);
00364     
00365     // read data
00366     for (int i = 0; i < length; i++) {
00367         buffer[i] = _spi.write(0xFF);
00368     }
00369     _spi.write(0xFF); // checksum
00370     _spi.write(0xFF);
00371     
00372     _cs = 1;
00373     _spi.write(0xFF);
00374     return 0;
00375 }
00376 
00377 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00378     _cs = 0;
00379     
00380     // indicate start of block
00381     _spi.write(0xFE);
00382     
00383     // write the data
00384     for (int i = 0; i < length; i++) {
00385         _spi.write(buffer[i]);
00386     }
00387     
00388     // write the checksum
00389     _spi.write(0xFF);
00390     _spi.write(0xFF);
00391     
00392     // check the response token
00393     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00394         _cs = 1;
00395         _spi.write(0xFF);
00396         return 1;
00397     }
00398     
00399     // wait for write to finish
00400     while (_spi.write(0xFF) == 0);
00401     
00402     _cs = 1;
00403     _spi.write(0xFF);
00404     return 0;
00405 }
00406 
00407 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00408     uint32_t bits = 0;
00409     uint32_t size = 1 + msb - lsb;
00410     for (int i = 0; i < size; i++) {
00411         uint32_t position = lsb + i;
00412         uint32_t byte = 15 - (position >> 3);
00413         uint32_t bit = position & 0x7;
00414         uint32_t value = (data[byte] >> bit) & 1;
00415         bits |= value << i;
00416     }
00417     return bits;
00418 }
00419 
00420 uint64_t SDFileSystem::_sd_sectors() {
00421     uint32_t c_size, c_size_mult, read_bl_len;
00422     uint32_t block_len, mult, blocknr, capacity;
00423     uint32_t hc_c_size;
00424     uint64_t blocks;
00425     
00426     // CMD9, Response R2 (R1 byte + 16-byte block read)
00427     if (_cmdx(9, 0) != 0) {
00428         debug("Didn't get a response from the disk\n");
00429         return 0;
00430     }
00431     
00432     uint8_t csd[16];
00433     if (_read(csd, 16) != 0) {
00434         debug("Couldn't read csd response from disk\n");
00435         return 0;
00436     }
00437     
00438     // csd_structure : csd[127:126]
00439     // c_size        : csd[73:62]
00440     // c_size_mult   : csd[49:47]
00441     // read_bl_len   : csd[83:80] - the *maximum* read block length
00442     
00443     int csd_structure = ext_bits(csd, 127, 126);
00444     
00445     switch (csd_structure) {
00446         case 0:
00447             cdv = 512;
00448             c_size = ext_bits(csd, 73, 62);
00449             c_size_mult = ext_bits(csd, 49, 47);
00450             read_bl_len = ext_bits(csd, 83, 80);
00451             
00452             block_len = 1 << read_bl_len;
00453             mult = 1 << (c_size_mult + 2);
00454             blocknr = (c_size + 1) * mult;
00455             capacity = blocknr * block_len;
00456             blocks = capacity / 512;
00457             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00458             break;
00459         
00460         case 1:
00461             cdv = 1;
00462             hc_c_size = ext_bits(csd, 63, 48);
00463             blocks = (hc_c_size+1)*1024;
00464             debug_if(SD_DBG, "\n\rSDHC Card \n\rhc_c_size: %d\n\rcapacity: %lld \n\rsectors: %lld\n\r", hc_c_size, blocks*512, blocks);
00465             break;
00466         
00467         default:
00468             debug("CSD struct unsupported\r\n");
00469             return 0;
00470     };
00471     return blocks;
00472 }