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.h"
00118 #include "mbed_debug.h"
00119 
00120 #define SD_COMMAND_TIMEOUT 5000
00121 
00122 #define SD_DBG             0
00123 
00124 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
00125     FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
00126     _cs = 1;
00127 }
00128 
00129 #define R1_IDLE_STATE           (1 << 0)
00130 #define R1_ERASE_RESET          (1 << 1)
00131 #define R1_ILLEGAL_COMMAND      (1 << 2)
00132 #define R1_COM_CRC_ERROR        (1 << 3)
00133 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00134 #define R1_ADDRESS_ERROR        (1 << 5)
00135 #define R1_PARAMETER_ERROR      (1 << 6)
00136 
00137 // Types
00138 #define SDCARD_FAIL 0 //!< v1.x Standard Capacity
00139 #define SDCARD_V1   1 //!< v2.x Standard Capacity
00140 #define SDCARD_V2   2 //!< v2.x High Capacity
00141 #define SDCARD_V2HC 3 //!< Not recognised as an SD Card
00142 
00143 int SDFileSystem::initialise_card() 
00144 {
00145         int numtries = 3;
00146         int res = 0;
00147         
00148         debug("Initializing SD/MMC card ...\r\n");
00149         while (numtries > 0)
00150         {
00151             // Set to 100kHz for initialisation, and clock card with cs = 1
00152             _spi.frequency(100000);
00153             _cs = 1;
00154             for (int i = 0; i < 16; i++) {
00155         _spi.write(0xFF);
00156             }
00157     
00158             // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00159             res = _cmd(0, 0); // software reset
00160             if (res == R1_IDLE_STATE) break;
00161             
00162             
00163             // Retry ... wait another 500 ms
00164             debug("Retrying ...\r\n");
00165             wait(0.5);
00166         }
00167         if (res != R1_IDLE_STATE) 
00168         {
00169                     debug("No disk, or could not put SD card in to SPI idle state\r\n");
00170                     return SDCARD_FAIL;
00171         }
00172     
00173     
00174     // send CMD8 to determine whther it is ver 2.x
00175     int r = _cmd8();
00176     if (r == R1_IDLE_STATE) {
00177         return initialise_card_v2();
00178     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00179         return initialise_card_v1();
00180     } else {
00181         debug("Not in idle state after sending CMD8 (not an SD card?)\r\n");
00182         return SDCARD_FAIL;
00183     }
00184 }
00185 
00186 int SDFileSystem::initialise_card_v1() {
00187     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00188         _cmd(55, 0);
00189         if (_cmd(41, 0) == 0) {
00190             cdv = 512;
00191             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00192             return SDCARD_V1;
00193         }
00194     }
00195     
00196     debug("Timeout waiting for v1.x card\n");
00197     return SDCARD_FAIL;
00198 }
00199 
00200 int SDFileSystem::initialise_card_v2() {
00201     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00202         wait_ms(50);
00203         _cmd58();
00204         _cmd(55, 0);
00205         if (_cmd(41, 0x40000000) == 0) {
00206             _cmd58();
00207             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00208             cdv = 1;
00209             return SDCARD_V2;
00210         }
00211     }
00212     
00213     debug("Timeout waiting for v2.x card\r\n");
00214     return SDCARD_FAIL;
00215 }
00216 
00217 int SDFileSystem::disk_initialize() {
00218     int i = initialise_card();
00219     debug_if(SD_DBG, "init card = %d\n", i);
00220     _sectors = _sd_sectors();
00221     
00222     // Set block length to 512 (CMD16)
00223     if (_cmd(16, 512) != 0) {
00224         debug("Set 512-byte block timed out\r\n");
00225         return 1;
00226     }
00227     
00228     _spi.frequency(1000000); // Set to 1MHz for data transfer
00229     return 0;
00230 }
00231 
00232 int SDFileSystem::disk_write(const uint8_t *buffer, uint64_t block_number) {
00233     // set write address for single block (CMD24)
00234     if (_cmd(24, block_number * cdv) != 0) {
00235         return 1;
00236     }
00237     
00238     // send the data block
00239     _write(buffer, 512);
00240     return 0;
00241 }
00242 
00243 int SDFileSystem::disk_read(uint8_t *buffer, uint64_t block_number) {
00244     // set read address for single block (CMD17)
00245     if (_cmd(17, block_number * cdv) != 0) {
00246         return 1;
00247     }
00248     
00249     // receive the data
00250     _read(buffer, 512);
00251     return 0;
00252 }
00253 
00254 int SDFileSystem::disk_status() { return 0; }
00255 int SDFileSystem::disk_sync() { return 0; }
00256 uint64_t SDFileSystem::disk_sectors() { return _sectors; }
00257 
00258 
00259 // PRIVATE FUNCTIONS
00260 int SDFileSystem::_cmd(int cmd, int arg) {
00261     _cs = 0;
00262     
00263     // send a command
00264     _spi.write(0x40 | cmd);
00265     _spi.write(arg >> 24);
00266     _spi.write(arg >> 16);
00267     _spi.write(arg >> 8);
00268     _spi.write(arg >> 0);
00269     _spi.write(0x95);
00270     
00271     // wait for the repsonse (response[7] == 0)
00272     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00273         int response = _spi.write(0xFF);
00274         if (!(response & 0x80)) {
00275             _cs = 1;
00276             _spi.write(0xFF);
00277             return response;
00278         }
00279     }
00280     _cs = 1;
00281     _spi.write(0xFF);
00282     return -1; // timeout
00283 }
00284 int SDFileSystem::_cmdx(int cmd, int arg) {
00285     _cs = 0;
00286     
00287     // send a command
00288     _spi.write(0x40 | cmd);
00289     _spi.write(arg >> 24);
00290     _spi.write(arg >> 16);
00291     _spi.write(arg >> 8);
00292     _spi.write(arg >> 0);
00293     _spi.write(0x95);
00294     
00295     // wait for the repsonse (response[7] == 0)
00296     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00297         int response = _spi.write(0xFF);
00298         if (!(response & 0x80)) {
00299             return response;
00300         }
00301     }
00302     _cs = 1;
00303     _spi.write(0xFF);
00304     return -1; // timeout
00305 }
00306 
00307 
00308 int SDFileSystem::_cmd58() {
00309     _cs = 0;
00310     int arg = 0;
00311     
00312     // send a command
00313     _spi.write(0x40 | 58);
00314     _spi.write(arg >> 24);
00315     _spi.write(arg >> 16);
00316     _spi.write(arg >> 8);
00317     _spi.write(arg >> 0);
00318     _spi.write(0x95);
00319     
00320     // wait for the repsonse (response[7] == 0)
00321     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00322         int response = _spi.write(0xFF);
00323         if (!(response & 0x80)) {
00324             int ocr = _spi.write(0xFF) << 24;
00325             ocr |= _spi.write(0xFF) << 16;
00326             ocr |= _spi.write(0xFF) << 8;
00327             ocr |= _spi.write(0xFF) << 0;
00328             _cs = 1;
00329             _spi.write(0xFF);
00330             return response;
00331         }
00332     }
00333     _cs = 1;
00334     _spi.write(0xFF);
00335     return -1; // timeout
00336 }
00337 
00338 int SDFileSystem::_cmd8() {
00339     _cs = 0;
00340     
00341     // send a command
00342     _spi.write(0x40 | 8); // CMD8
00343     _spi.write(0x00);     // reserved
00344     _spi.write(0x00);     // reserved
00345     _spi.write(0x01);     // 3.3v
00346     _spi.write(0xAA);     // check pattern
00347     _spi.write(0x87);     // crc
00348     
00349     // wait for the repsonse (response[7] == 0)
00350     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00351         char response[5];
00352         response[0] = _spi.write(0xFF);
00353         if (!(response[0] & 0x80)) {
00354             for (int j = 1; j < 5; j++) {
00355                 response[i] = _spi.write(0xFF);
00356             }
00357             _cs = 1;
00358             _spi.write(0xFF);
00359             return response[0];
00360         }
00361     }
00362     _cs = 1;
00363     _spi.write(0xFF);
00364     return -1; // timeout
00365 }
00366 
00367 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00368     _cs = 0;
00369     
00370     // read until start byte (0xFF)
00371     while (_spi.write(0xFF) != 0xFE);
00372     
00373     // read data
00374     for (int i = 0; i < length; i++) {
00375         buffer[i] = _spi.write(0xFF);
00376     }
00377     _spi.write(0xFF); // checksum
00378     _spi.write(0xFF);
00379     
00380     _cs = 1;
00381     _spi.write(0xFF);
00382     return 0;
00383 }
00384 
00385 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00386     _cs = 0;
00387     
00388     // indicate start of block
00389     _spi.write(0xFE);
00390     
00391     // write the data
00392     for (int i = 0; i < length; i++) {
00393         _spi.write(buffer[i]);
00394     }
00395     
00396     // write the checksum
00397     _spi.write(0xFF);
00398     _spi.write(0xFF);
00399     
00400     // check the response token
00401     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00402         _cs = 1;
00403         _spi.write(0xFF);
00404         return 1;
00405     }
00406     
00407     // wait for write to finish
00408     while (_spi.write(0xFF) == 0);
00409     
00410     _cs = 1;
00411     _spi.write(0xFF);
00412     return 0;
00413 }
00414 
00415 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00416     uint32_t bits = 0;
00417     uint32_t size = 1 + msb - lsb;
00418     for (int i = 0; i < size; i++) {
00419         uint32_t position = lsb + i;
00420         uint32_t byte = 15 - (position >> 3);
00421         uint32_t bit = position & 0x7;
00422         uint32_t value = (data[byte] >> bit) & 1;
00423         bits |= value << i;
00424     }
00425     return bits;
00426 }
00427 
00428 uint64_t SDFileSystem::_sd_sectors() {
00429     uint32_t c_size, c_size_mult, read_bl_len;
00430     uint32_t block_len, mult, blocknr, capacity;
00431     uint32_t hc_c_size;
00432     uint64_t blocks;
00433     
00434     // CMD9, Response R2 (R1 byte + 16-byte block read)
00435     if (_cmdx(9, 0) != 0) {
00436         debug("Didn't get a response from the disk\n");
00437         return 0;
00438     }
00439     
00440     uint8_t csd[16];
00441     if (_read(csd, 16) != 0) {
00442         debug("Couldn't read csd response from disk\n");
00443         return 0;
00444     }
00445     
00446     // csd_structure : csd[127:126]
00447     // c_size        : csd[73:62]
00448     // c_size_mult   : csd[49:47]
00449     // read_bl_len   : csd[83:80] - the *maximum* read block length
00450     
00451     int csd_structure = ext_bits(csd, 127, 126);
00452     
00453     switch (csd_structure) {
00454         case 0:
00455             cdv = 512;
00456             c_size = ext_bits(csd, 73, 62);
00457             c_size_mult = ext_bits(csd, 49, 47);
00458             read_bl_len = ext_bits(csd, 83, 80);
00459             
00460             block_len = 1 << read_bl_len;
00461             mult = 1 << (c_size_mult + 2);
00462             blocknr = (c_size + 1) * mult;
00463             capacity = blocknr * block_len;
00464             blocks = capacity / 512;
00465             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00466             break;
00467         
00468         case 1:
00469             cdv = 1;
00470             hc_c_size = ext_bits(csd, 63, 48);
00471             blocks = (hc_c_size+1)*1024;
00472             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);
00473             break;
00474         
00475         default:
00476             debug("CSD struct unsupported\r\n");
00477             return 0;
00478     };
00479     return blocks;
00480 }
00481