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_debug.h"
00117 
00118 #define SD_COMMAND_TIMEOUT 5000
00119 
00120 #define SD_DBG             0
00121 
00122 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
00123     FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs), _is_initialized(0) {
00124     _cs = 1;
00125 
00126     // Set default to 100kHz for initialisation and 1MHz for data transfer
00127     _init_sck       = 125000;
00128     _transfer_sck   = 1000000;
00129 }
00130 
00131 #define R1_IDLE_STATE           (1 << 0)
00132 #define R1_ERASE_RESET          (1 << 1)
00133 #define R1_ILLEGAL_COMMAND      (1 << 2)
00134 #define R1_COM_CRC_ERROR        (1 << 3)
00135 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00136 #define R1_ADDRESS_ERROR        (1 << 5)
00137 #define R1_PARAMETER_ERROR      (1 << 6)
00138 
00139 // Types
00140 //  - v1.x Standard Capacity
00141 //  - v2.x Standard Capacity
00142 //  - v2.x High Capacity
00143 //  - Not recognised as an SD Card
00144 #define SDCARD_FAIL 0
00145 #define SDCARD_V1   1
00146 #define SDCARD_V2   2
00147 #define SDCARD_V2HC 3
00148 
00149 int SDFileSystem::initialise_card() {
00150     // Set to SCK for initialisation, and clock card with cs = 1
00151     
00152     _spi.format(8,3);    //DEBUG
00153     
00154     _spi.frequency(_init_sck);
00155     _cs = 1;
00156     for (int i = 0; i < 16; i++) {
00157         _spi.write(0xFF);
00158     }
00159 
00160     // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00161     if (_cmd(0, 0) != 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     int 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     _is_initialized = initialise_card();
00211     if (_is_initialized == 0) {
00212         debug("Fail to initialize card\n");
00213         return 1;
00214     }
00215     debug_if(SD_DBG, "init card = %d\n", _is_initialized);
00216     _sectors = _sd_sectors();
00217 
00218     // Set block length to 512 (CMD16)
00219     if (_cmd(16, 512) != 0) {
00220         debug("Set 512-byte block timed out\n");
00221         return 1;
00222     }
00223 
00224     // Set SCK for data transfer
00225     _spi.frequency(_transfer_sck);
00226     
00227     _spi.format(8,3);    //DEBUG
00228     
00229     return 0;
00230 }
00231 
00232 int SDFileSystem::disk_write(const uint8_t* buffer, uint32_t block_number, uint32_t count) {
00233     if (!_is_initialized) {
00234         return -1;
00235     }
00236     
00237     for (uint32_t b = block_number; b < block_number + count; b++) {
00238         // set write address for single block (CMD24)
00239         if (_cmd(24, b * cdv) != 0) {
00240             return 1;
00241         }
00242         
00243         // send the data block
00244         _write(buffer, 512);
00245         buffer += 512;
00246     }
00247     
00248     return 0;
00249 }
00250 
00251 int SDFileSystem::disk_read(uint8_t* buffer, uint32_t block_number, uint32_t count) {
00252     if (!_is_initialized) {
00253         return -1;
00254     }
00255     
00256     for (uint32_t b = block_number; b < block_number + count; b++) {
00257         // set read address for single block (CMD17)
00258         if (_cmd(17, b * cdv) != 0) {
00259             return 1;
00260         }
00261         
00262         // receive the data
00263         _read(buffer, 512);
00264         buffer += 512;
00265     }
00266 
00267     return 0;
00268 }
00269 
00270 int SDFileSystem::disk_status() {
00271     // FATFileSystem::disk_status() returns 0 when initialized
00272     if (_is_initialized) {
00273         return 0;
00274     } else {
00275         return 1;
00276     }
00277 }
00278 
00279 int SDFileSystem::disk_sync() { return 0; }
00280 uint32_t SDFileSystem::disk_sectors() { return _sectors; }
00281 
00282 
00283 // PRIVATE FUNCTIONS
00284 int SDFileSystem::_cmd(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             _cs = 1;
00300             _spi.write(0xFF);
00301             return response;
00302         }
00303     }
00304     _cs = 1;
00305     _spi.write(0xFF);
00306     return -1; // timeout
00307 }
00308 int SDFileSystem::_cmdx(int cmd, int arg) {
00309     _cs = 0;
00310 
00311     // send a command
00312     _spi.write(0x40 | cmd);
00313     _spi.write(arg >> 24);
00314     _spi.write(arg >> 16);
00315     _spi.write(arg >> 8);
00316     _spi.write(arg >> 0);
00317     _spi.write(0x95);
00318 
00319     // wait for the repsonse (response[7] == 0)
00320     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00321         int response = _spi.write(0xFF);
00322         if (!(response & 0x80)) {
00323             return response;
00324         }
00325     }
00326     _cs = 1;
00327     _spi.write(0xFF);
00328     return -1; // timeout
00329 }
00330 
00331 
00332 int SDFileSystem::_cmd58() {
00333     _cs = 0;
00334     int arg = 0;
00335 
00336     // send a command
00337     _spi.write(0x40 | 58);
00338     _spi.write(arg >> 24);
00339     _spi.write(arg >> 16);
00340     _spi.write(arg >> 8);
00341     _spi.write(arg >> 0);
00342     _spi.write(0x95);
00343 
00344     // wait for the repsonse (response[7] == 0)
00345     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00346         int response = _spi.write(0xFF);
00347         if (!(response & 0x80)) {
00348             int ocr = _spi.write(0xFF) << 24;
00349             ocr |= _spi.write(0xFF) << 16;
00350             ocr |= _spi.write(0xFF) << 8;
00351             ocr |= _spi.write(0xFF) << 0;
00352             _cs = 1;
00353             _spi.write(0xFF);
00354             return response;
00355         }
00356     }
00357     _cs = 1;
00358     _spi.write(0xFF);
00359     return -1; // timeout
00360 }
00361 
00362 int SDFileSystem::_cmd8() {
00363     _cs = 0;
00364 
00365     // send a command
00366     _spi.write(0x40 | 8); // CMD8
00367     _spi.write(0x00);     // reserved
00368     _spi.write(0x00);     // reserved
00369     _spi.write(0x01);     // 3.3v
00370     _spi.write(0xAA);     // check pattern
00371     _spi.write(0x87);     // crc
00372 
00373     // wait for the repsonse (response[7] == 0)
00374     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00375         char response[5];
00376         response[0] = _spi.write(0xFF);
00377         if (!(response[0] & 0x80)) {
00378             for (int j = 1; j < 5; j++) {
00379                 response[i] = _spi.write(0xFF);
00380             }
00381             _cs = 1;
00382             _spi.write(0xFF);
00383             return response[0];
00384         }
00385     }
00386     _cs = 1;
00387     _spi.write(0xFF);
00388     return -1; // timeout
00389 }
00390 
00391 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00392     _cs = 0;
00393 
00394     // read until start byte (0xFF)
00395     while (_spi.write(0xFF) != 0xFE);
00396 
00397     // read data
00398     for (uint32_t i = 0; i < length; i++) {
00399         buffer[i] = _spi.write(0xFF);
00400     }
00401     _spi.write(0xFF); // checksum
00402     _spi.write(0xFF);
00403 
00404     _cs = 1;
00405     _spi.write(0xFF);
00406     return 0;
00407 }
00408 
00409 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00410     _cs = 0;
00411 
00412     // indicate start of block
00413     _spi.write(0xFE);
00414 
00415     // write the data
00416     for (uint32_t i = 0; i < length; i++) {
00417         _spi.write(buffer[i]);
00418     }
00419 
00420     // write the checksum
00421     _spi.write(0xFF);
00422     _spi.write(0xFF);
00423 
00424     // check the response token
00425     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00426         _cs = 1;
00427         _spi.write(0xFF);
00428         return 1;
00429     }
00430 
00431     // wait for write to finish
00432     while (_spi.write(0xFF) == 0);
00433 
00434     _cs = 1;
00435     _spi.write(0xFF);
00436     return 0;
00437 }
00438 
00439 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00440     uint32_t bits = 0;
00441     uint32_t size = 1 + msb - lsb;
00442     for (uint32_t i = 0; i < size; i++) {
00443         uint32_t position = lsb + i;
00444         uint32_t byte = 15 - (position >> 3);
00445         uint32_t bit = position & 0x7;
00446         uint32_t value = (data[byte] >> bit) & 1;
00447         bits |= value << i;
00448     }
00449     return bits;
00450 }
00451 
00452 uint32_t SDFileSystem::_sd_sectors() {
00453     uint32_t c_size, c_size_mult, read_bl_len;
00454     uint32_t block_len, mult, blocknr, capacity;
00455     uint32_t hc_c_size;
00456     uint32_t blocks;
00457 
00458     // CMD9, Response R2 (R1 byte + 16-byte block read)
00459     if (_cmdx(9, 0) != 0) {
00460         debug("Didn't get a response from the disk\n");
00461         return 0;
00462     }
00463 
00464     uint8_t csd[16];
00465     if (_read(csd, 16) != 0) {
00466         debug("Couldn't read csd response from disk\n");
00467         return 0;
00468     }
00469 
00470     // csd_structure : csd[127:126]
00471     // c_size        : csd[73:62]
00472     // c_size_mult   : csd[49:47]
00473     // read_bl_len   : csd[83:80] - the *maximum* read block length
00474 
00475     int csd_structure = ext_bits(csd, 127, 126);
00476 
00477     switch (csd_structure) {
00478         case 0:
00479             cdv = 512;
00480             c_size = ext_bits(csd, 73, 62);
00481             c_size_mult = ext_bits(csd, 49, 47);
00482             read_bl_len = ext_bits(csd, 83, 80);
00483 
00484             block_len = 1 << read_bl_len;
00485             mult = 1 << (c_size_mult + 2);
00486             blocknr = (c_size + 1) * mult;
00487             capacity = blocknr * block_len;
00488             blocks = capacity / 512;
00489             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00490             break;
00491 
00492         case 1:
00493             cdv = 1;
00494             hc_c_size = ext_bits(csd, 63, 48);
00495             blocks = (hc_c_size+1)*1024;
00496             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);
00497             break;
00498 
00499         default:
00500             debug("CSD struct unsupported\r\n");
00501             return 0;
00502     };
00503     return blocks;
00504 }