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 /* Introduction
00023  * ------------
00024  * SD and MMC cards support a number of interfaces, but common to them all
00025  * is one based on SPI. This is the one I'm implmenting because it means
00026  * it is much more portable even though not so performant, and we already
00027  * have the mbed SPI Interface!
00028  *
00029  * The main reference I'm using is Chapter 7, "SPI Mode" of:
00030  *  http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
00031  *
00032  * SPI Startup
00033  * -----------
00034  * The SD card powers up in SD mode. The SPI interface mode is selected by
00035  * asserting CS low and sending the reset command (CMD0). The card will
00036  * respond with a (R1) response.
00037  *
00038  * CMD8 is optionally sent to determine the voltage range supported, and
00039  * indirectly determine whether it is a version 1.x SD/non-SD card or
00040  * version 2.x. I'll just ignore this for now.
00041  *
00042  * ACMD41 is repeatedly issued to initialise the card, until "in idle"
00043  * (bit 0) of the R1 response goes to '0', indicating it is initialised.
00044  *
00045  * You should also indicate whether the host supports High Capicity cards,
00046  * and check whether the card is high capacity - i'll also ignore this
00047  *
00048  * SPI Protocol
00049  * ------------
00050  * The SD SPI protocol is based on transactions made up of 8-bit words, with
00051  * the host starting every bus transaction by asserting the CS signal low. The
00052  * card always responds to commands, data blocks and errors.
00053  *
00054  * The protocol supports a CRC, but by default it is off (except for the
00055  * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
00056  * I'll leave the CRC off I think!
00057  *
00058  * Standard capacity cards have variable data block sizes, whereas High
00059  * Capacity cards fix the size of data block to 512 bytes. I'll therefore
00060  * just always use the Standard Capacity cards with a block size of 512 bytes.
00061  * This is set with CMD16.
00062  *
00063  * You can read and write single blocks (CMD17, CMD25) or multiple blocks
00064  * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
00065  * the card gets a read command, it responds with a response token, and then
00066  * a data token or an error.
00067  *
00068  * SPI Command Format
00069  * ------------------
00070  * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
00071  *
00072  * +---------------+------------+------------+-----------+----------+--------------+
00073  * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
00074  * +---------------+------------+------------+-----------+----------+--------------+
00075  *
00076  * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
00077  *
00078  * All Application Specific commands shall be preceded with APP_CMD (CMD55).
00079  *
00080  * SPI Response Format
00081  * -------------------
00082  * The main response format (R1) is a status byte (normally zero). Key flags:
00083  *  idle - 1 if the card is in an idle state/initialising
00084  *  cmd  - 1 if an illegal command code was detected
00085  *
00086  *    +-------------------------------------------------+
00087  * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
00088  *    +-------------------------------------------------+
00089  *
00090  * R1b is the same, except it is followed by a busy signal (zeros) until
00091  * the first non-zero byte when it is ready again.
00092  *
00093  * Data Response Token
00094  * -------------------
00095  * Every data block written to the card is acknowledged by a byte
00096  * response token
00097  *
00098  * +----------------------+
00099  * | xxx | 0 | status | 1 |
00100  * +----------------------+
00101  *              010 - OK!
00102  *              101 - CRC Error
00103  *              110 - Write Error
00104  *
00105  * Single Block Read and Write
00106  * ---------------------------
00107  *
00108  * Block transfers have a byte header, followed by the data, followed
00109  * by a 16-bit CRC. In our case, the data will always be 512 bytes.
00110  *
00111  * +------+---------+---------+- -  - -+---------+-----------+----------+
00112  * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
00113  * +------+---------+---------+- -  - -+---------+-----------+----------+
00114  */
00115 #include "SDFileSystem.h"
00116 #include "mbed.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, PinName cd, const char* name) :
00124     FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs), _cd(cd){
00125     _cs = 1;
00126     _cd.mode(PullUp);
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 //  - v1.x Standard Capacity
00139 //  - v2.x Standard Capacity
00140 //  - v2.x High Capacity
00141 //  - Not recognised as an SD Card
00142 #define SDCARD_FAIL 0
00143 #define SDCARD_V1   1
00144 #define SDCARD_V2   2
00145 #define SDCARD_V2HC 3
00146 
00147 int SDFileSystem::initialise_card() {
00148     // Set to 100kHz for initialisation, and clock card with cs = 1
00149     _spi.frequency(100000);
00150     _cs = 1;
00151     for (int i = 0; i < 16; i++) {
00152         _spi.write(0xFF);
00153     }
00154     
00155     // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00156     if (_cmd(0, 0) != R1_IDLE_STATE) {
00157         debug("No disk, or could not put SD card in to SPI idle state\n");
00158         return SDCARD_FAIL;
00159     }
00160     
00161     // send CMD8 to determine whther it is ver 2.x
00162     int r = _cmd8();
00163     if (r == R1_IDLE_STATE) {
00164         return initialise_card_v2();
00165     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00166         return initialise_card_v1();
00167     } else {
00168         debug("Not in idle state after sending CMD8 (not an SD card?)\n");
00169         return SDCARD_FAIL;
00170     }
00171 }
00172 
00173 int SDFileSystem::initialise_card_v1() {
00174     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00175         _cmd(55, 0);
00176         if (_cmd(41, 0) == 0) {
00177             cdv = 512;
00178             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00179             return SDCARD_V1;
00180         }
00181     }
00182     
00183     debug("Timeout waiting for v1.x card\n");
00184     return SDCARD_FAIL;
00185 }
00186 
00187 bool SDFileSystem::SD_inserted()
00188 {
00189         if(_cd) {
00190             return(true);
00191         }
00192         else
00193         {return(false);}
00194 }
00195 int SDFileSystem::initialise_card_v2() {
00196     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00197         wait_ms(50);
00198         _cmd58();
00199         _cmd(55, 0);
00200         if (_cmd(41, 0x40000000) == 0) {
00201             _cmd58();
00202             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00203             cdv = 1;
00204             return SDCARD_V2;
00205         }
00206     }
00207     
00208     debug("Timeout waiting for v2.x card\n");
00209     return SDCARD_FAIL;
00210 }
00211 
00212 int SDFileSystem::disk_initialize() {
00213     int i = initialise_card();
00214     debug_if(SD_DBG, "init card = %d\n", i);
00215     _sectors = _sd_sectors();
00216     
00217     // Set block length to 512 (CMD16)
00218     if (_cmd(16, 512) != 0) {
00219         debug("Set 512-byte block timed out\n");
00220         return 1;
00221     }
00222     
00223     _spi.frequency(1000000); // Set to 1MHz for data transfer
00224     return 0;
00225 }
00226 
00227 int SDFileSystem::disk_write(const uint8_t *buffer, uint64_t block_number) {
00228     // set write address for single block (CMD24)
00229     if (_cmd(24, block_number * cdv) != 0) {
00230         return 1;
00231     }
00232     
00233     // send the data block
00234     _write(buffer, 512);
00235     return 0;
00236 }
00237 
00238 int SDFileSystem::disk_read(uint8_t *buffer, uint64_t block_number) {
00239     // set read address for single block (CMD17)
00240     if (_cmd(17, block_number * cdv) != 0) {
00241         return 1;
00242     }
00243     
00244     // receive the data
00245     _read(buffer, 512);
00246     return 0;
00247 }
00248 
00249 int SDFileSystem::disk_status() { return 0; }
00250 int SDFileSystem::disk_sync() { return 0; }
00251 uint64_t SDFileSystem::disk_sectors() { return _sectors; }
00252 
00253 
00254 // PRIVATE FUNCTIONS
00255 int SDFileSystem::_cmd(int cmd, int arg) {
00256     _cs = 0;
00257     
00258     // send a command
00259     _spi.write(0x40 | cmd);
00260     _spi.write(arg >> 24);
00261     _spi.write(arg >> 16);
00262     _spi.write(arg >> 8);
00263     _spi.write(arg >> 0);
00264     _spi.write(0x95);
00265     
00266     // wait for the repsonse (response[7] == 0)
00267     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00268         int response = _spi.write(0xFF);
00269         if (!(response & 0x80)) {
00270             _cs = 1;
00271             _spi.write(0xFF);
00272             return response;
00273         }
00274     }
00275     _cs = 1;
00276     _spi.write(0xFF);
00277     return -1; // timeout
00278 }
00279 int SDFileSystem::_cmdx(int cmd, int arg) {
00280     _cs = 0;
00281     
00282     // send a command
00283     _spi.write(0x40 | cmd);
00284     _spi.write(arg >> 24);
00285     _spi.write(arg >> 16);
00286     _spi.write(arg >> 8);
00287     _spi.write(arg >> 0);
00288     _spi.write(0x95);
00289     
00290     // wait for the repsonse (response[7] == 0)
00291     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00292         int response = _spi.write(0xFF);
00293         if (!(response & 0x80)) {
00294             return response;
00295         }
00296     }
00297     _cs = 1;
00298     _spi.write(0xFF);
00299     return -1; // timeout
00300 }
00301 
00302 
00303 int SDFileSystem::_cmd58() {
00304     _cs = 0;
00305     int arg = 0;
00306     
00307     // send a command
00308     _spi.write(0x40 | 58);
00309     _spi.write(arg >> 24);
00310     _spi.write(arg >> 16);
00311     _spi.write(arg >> 8);
00312     _spi.write(arg >> 0);
00313     _spi.write(0x95);
00314     
00315     // wait for the repsonse (response[7] == 0)
00316     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00317         int response = _spi.write(0xFF);
00318         if (!(response & 0x80)) {
00319             int ocr = _spi.write(0xFF) << 24;
00320             ocr |= _spi.write(0xFF) << 16;
00321             ocr |= _spi.write(0xFF) << 8;
00322             ocr |= _spi.write(0xFF) << 0;
00323             _cs = 1;
00324             _spi.write(0xFF);
00325             return response;
00326         }
00327     }
00328     _cs = 1;
00329     _spi.write(0xFF);
00330     return -1; // timeout
00331 }
00332 
00333 int SDFileSystem::_cmd8() {
00334     _cs = 0;
00335     
00336     // send a command
00337     _spi.write(0x40 | 8); // CMD8
00338     _spi.write(0x00);     // reserved
00339     _spi.write(0x00);     // reserved
00340     _spi.write(0x01);     // 3.3v
00341     _spi.write(0xAA);     // check pattern
00342     _spi.write(0x87);     // crc
00343     
00344     // wait for the repsonse (response[7] == 0)
00345     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00346         char response[5];
00347         response[0] = _spi.write(0xFF);
00348         if (!(response[0] & 0x80)) {
00349             for (int j = 1; j < 5; j++) {
00350                 response[i] = _spi.write(0xFF);
00351             }
00352             _cs = 1;
00353             _spi.write(0xFF);
00354             return response[0];
00355         }
00356     }
00357     _cs = 1;
00358     _spi.write(0xFF);
00359     return -1; // timeout
00360 }
00361 
00362 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00363     _cs = 0;
00364     
00365     // read until start byte (0xFF)
00366     while (_spi.write(0xFF) != 0xFE);
00367     
00368     // read data
00369     for (int i = 0; i < length; i++) {
00370         buffer[i] = _spi.write(0xFF);
00371     }
00372     _spi.write(0xFF); // checksum
00373     _spi.write(0xFF);
00374     
00375     _cs = 1;
00376     _spi.write(0xFF);
00377     return 0;
00378 }
00379 
00380 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00381     _cs = 0;
00382     
00383     // indicate start of block
00384     _spi.write(0xFE);
00385     
00386     // write the data
00387     for (int i = 0; i < length; i++) {
00388         _spi.write(buffer[i]);
00389     }
00390     
00391     // write the checksum
00392     _spi.write(0xFF);
00393     _spi.write(0xFF);
00394     
00395     // check the response token
00396     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00397         _cs = 1;
00398         _spi.write(0xFF);
00399         return 1;
00400     }
00401     
00402     // wait for write to finish
00403     while (_spi.write(0xFF) == 0);
00404     
00405     _cs = 1;
00406     _spi.write(0xFF);
00407     return 0;
00408 }
00409 
00410 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00411     uint32_t bits = 0;
00412     uint32_t size = 1 + msb - lsb;
00413     for (int i = 0; i < size; i++) {
00414         uint32_t position = lsb + i;
00415         uint32_t byte = 15 - (position >> 3);
00416         uint32_t bit = position & 0x7;
00417         uint32_t value = (data[byte] >> bit) & 1;
00418         bits |= value << i;
00419     }
00420     return bits;
00421 }
00422 
00423 uint64_t SDFileSystem::_sd_sectors() {
00424     uint32_t c_size, c_size_mult, read_bl_len;
00425     uint32_t block_len, mult, blocknr, capacity;
00426     uint32_t hc_c_size;
00427     uint64_t blocks;
00428     
00429     // CMD9, Response R2 (R1 byte + 16-byte block read)
00430     if (_cmdx(9, 0) != 0) {
00431         debug("Didn't get a response from the disk\n");
00432         return 0;
00433     }
00434     
00435     uint8_t csd[16];
00436     if (_read(csd, 16) != 0) {
00437         debug("Couldn't read csd response from disk\n");
00438         return 0;
00439     }
00440     
00441     // csd_structure : csd[127:126]
00442     // c_size        : csd[73:62]
00443     // c_size_mult   : csd[49:47]
00444     // read_bl_len   : csd[83:80] - the *maximum* read block length
00445     
00446     int csd_structure = ext_bits(csd, 127, 126);
00447     
00448     switch (csd_structure) {
00449         case 0:
00450             cdv = 512;
00451             c_size = ext_bits(csd, 73, 62);
00452             c_size_mult = ext_bits(csd, 49, 47);
00453             read_bl_len = ext_bits(csd, 83, 80);
00454             
00455             block_len = 1 << read_bl_len;
00456             mult = 1 << (c_size_mult + 2);
00457             blocknr = (c_size + 1) * mult;
00458             capacity = blocknr * block_len;
00459             blocks = capacity / 512;
00460             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00461             break;
00462         
00463         case 1:
00464             cdv = 1;
00465             hc_c_size = ext_bits(csd, 63, 48);
00466             blocks = (hc_c_size+1)*1024;
00467             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);
00468             break;
00469         
00470         default:
00471             debug("CSD struct unsupported\r\n");
00472             return 0;
00473     };
00474     return blocks;
00475 }