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 = 100000;
00128     //_transfer_sck = 1000000;
00129     _init_sck = 375000;
00130     _transfer_sck = 1000000;
00131 }
00132 
00133 #define R1_IDLE_STATE           (1 << 0)
00134 #define R1_ERASE_RESET          (1 << 1)
00135 #define R1_ILLEGAL_COMMAND      (1 << 2)
00136 #define R1_COM_CRC_ERROR        (1 << 3)
00137 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00138 #define R1_ADDRESS_ERROR        (1 << 5)
00139 #define R1_PARAMETER_ERROR      (1 << 6)
00140 
00141 // Types
00142 //  - v1.x Standard Capacity
00143 //  - v2.x Standard Capacity
00144 //  - v2.x High Capacity
00145 //  - Not recognised as an SD Card
00146 #define SDCARD_FAIL 0
00147 #define SDCARD_V1   1
00148 #define SDCARD_V2   2
00149 #define SDCARD_V2HC 3
00150 
00151 int SDFileSystem::initialise_card() {
00152     // Set to SCK for initialisation, and clock card with cs = 1
00153     _spi.frequency(_init_sck);
00154     _cs = 1;
00155     for (int i = 0; i < 16; i++) {
00156         _spi.write(0xFF);
00157     }
00158 
00159     // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00160     if (_cmd(0, 0) != R1_IDLE_STATE) {
00161         debug("No disk, or could not put SD card in to SPI idle state\n");
00162         return SDCARD_FAIL;
00163     }
00164 
00165     // send CMD8 to determine whther it is ver 2.x
00166     int r = _cmd8();
00167     if (r == R1_IDLE_STATE) {
00168         return initialise_card_v2();
00169     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00170         return initialise_card_v1();
00171     } else {
00172         debug("Not in idle state after sending CMD8 (not an SD card?)\n");
00173         return SDCARD_FAIL;
00174     }
00175 }
00176 
00177 int SDFileSystem::initialise_card_v1() {
00178     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00179         _cmd(55, 0);
00180         if (_cmd(41, 0) == 0) {
00181             cdv = 512;
00182             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00183             return SDCARD_V1;
00184         }
00185     }
00186 
00187     debug("Timeout waiting for v1.x card\n");
00188     return SDCARD_FAIL;
00189 }
00190 
00191 int SDFileSystem::initialise_card_v2() {
00192     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00193         wait_ms(50);
00194         _cmd58();
00195         _cmd(55, 0);
00196         if (_cmd(41, 0x40000000) == 0) {
00197             _cmd58();
00198             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00199             cdv = 1;
00200             return SDCARD_V2;
00201         }
00202     }
00203 
00204     debug("Timeout waiting for v2.x card\n");
00205     return SDCARD_FAIL;
00206 }
00207 
00208 int SDFileSystem::disk_initialize() {
00209     _is_initialized = initialise_card();
00210     if (_is_initialized == 0) {
00211         debug("Fail to initialize card\n");
00212         return 1;
00213     }
00214     debug_if(SD_DBG, "init card = %d\n", _is_initialized);
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     // Set SCK for data transfer
00224     _spi.frequency(_transfer_sck);
00225     return 0;
00226 }
00227 
00228 int SDFileSystem::disk_write(const uint8_t* buffer, uint32_t block_number, uint32_t count) {
00229     if (!_is_initialized) {
00230         return -1;
00231     }
00232     
00233     for (uint32_t b = block_number; b < block_number + count; b++) {
00234         // set write address for single block (CMD24)
00235         if (_cmd(24, b * cdv) != 0) {
00236             return 1;
00237         }
00238         
00239         // send the data block
00240         _write(buffer, 512);
00241         buffer += 512;
00242     }
00243     
00244     return 0;
00245 }
00246 
00247 int SDFileSystem::disk_read(uint8_t* buffer, uint32_t block_number, uint32_t count) {
00248     if (!_is_initialized) {
00249         return -1;
00250     }
00251     
00252     for (uint32_t b = block_number; b < block_number + count; b++) {
00253         // set read address for single block (CMD17)
00254         if (_cmd(17, b * cdv) != 0) {
00255             return 1;
00256         }
00257         
00258         // receive the data
00259         _read(buffer, 512);
00260         buffer += 512;
00261     }
00262 
00263     return 0;
00264 }
00265 
00266 int SDFileSystem::disk_status() {
00267     // FATFileSystem::disk_status() returns 0 when initialized
00268     if (_is_initialized) {
00269         return 0;
00270     } else {
00271         return 1;
00272     }
00273 }
00274 
00275 int SDFileSystem::disk_sync() { return 0; }
00276 uint32_t SDFileSystem::disk_sectors() { return _sectors; }
00277 
00278 
00279 // PRIVATE FUNCTIONS
00280 int SDFileSystem::_cmd(int cmd, int arg) {
00281     _cs = 0;
00282 
00283     // send a command
00284     _spi.write(0x40 | cmd);
00285     _spi.write(arg >> 24);
00286     _spi.write(arg >> 16);
00287     _spi.write(arg >> 8);
00288     _spi.write(arg >> 0);
00289     _spi.write(0x95);
00290 
00291     // wait for the repsonse (response[7] == 0)
00292     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00293         int response = _spi.write(0xFF);
00294         if (!(response & 0x80)) {
00295             _cs = 1;
00296             _spi.write(0xFF);
00297             return response;
00298         }
00299     }
00300     _cs = 1;
00301     _spi.write(0xFF);
00302     return -1; // timeout
00303 }
00304 int SDFileSystem::_cmdx(int cmd, int arg) {
00305     _cs = 0;
00306 
00307     // send a command
00308     _spi.write(0x40 | cmd);
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             return response;
00320         }
00321     }
00322     _cs = 1;
00323     _spi.write(0xFF);
00324     return -1; // timeout
00325 }
00326 
00327 
00328 int SDFileSystem::_cmd58() {
00329     _cs = 0;
00330     int arg = 0;
00331 
00332     // send a command
00333     _spi.write(0x40 | 58);
00334     _spi.write(arg >> 24);
00335     _spi.write(arg >> 16);
00336     _spi.write(arg >> 8);
00337     _spi.write(arg >> 0);
00338     _spi.write(0x95);
00339 
00340     // wait for the repsonse (response[7] == 0)
00341     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00342         int response = _spi.write(0xFF);
00343         if (!(response & 0x80)) {
00344             int ocr = _spi.write(0xFF) << 24;
00345             ocr |= _spi.write(0xFF) << 16;
00346             ocr |= _spi.write(0xFF) << 8;
00347             ocr |= _spi.write(0xFF) << 0;
00348             _cs = 1;
00349             _spi.write(0xFF);
00350             return response;
00351         }
00352     }
00353     _cs = 1;
00354     _spi.write(0xFF);
00355     return -1; // timeout
00356 }
00357 
00358 int SDFileSystem::_cmd8() {
00359     _cs = 0;
00360 
00361     // send a command
00362     _spi.write(0x40 | 8); // CMD8
00363     _spi.write(0x00);     // reserved
00364     _spi.write(0x00);     // reserved
00365     _spi.write(0x01);     // 3.3v
00366     _spi.write(0xAA);     // check pattern
00367     _spi.write(0x87);     // crc
00368 
00369     // wait for the repsonse (response[7] == 0)
00370     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00371         char response[5];
00372         response[0] = _spi.write(0xFF);
00373         if (!(response[0] & 0x80)) {
00374             for (int j = 1; j < 5; j++) {
00375                 response[i] = _spi.write(0xFF);
00376             }
00377             _cs = 1;
00378             _spi.write(0xFF);
00379             return response[0];
00380         }
00381     }
00382     _cs = 1;
00383     _spi.write(0xFF);
00384     return -1; // timeout
00385 }
00386 
00387 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00388     _cs = 0;
00389 
00390     // read until start byte (0xFF)
00391     while (_spi.write(0xFF) != 0xFE);
00392 
00393     // read data
00394     for (uint32_t i = 0; i < length; i++) {
00395         buffer[i] = _spi.write(0xFF);
00396     }
00397     _spi.write(0xFF); // checksum
00398     _spi.write(0xFF);
00399 
00400     _cs = 1;
00401     _spi.write(0xFF);
00402     return 0;
00403 }
00404 
00405 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00406     _cs = 0;
00407 
00408     // indicate start of block
00409     _spi.write(0xFE);
00410 
00411     // write the data
00412     for (uint32_t i = 0; i < length; i++) {
00413         _spi.write(buffer[i]);
00414     }
00415 
00416     // write the checksum
00417     _spi.write(0xFF);
00418     _spi.write(0xFF);
00419 
00420     // check the response token
00421     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00422         _cs = 1;
00423         _spi.write(0xFF);
00424         return 1;
00425     }
00426 
00427     // wait for write to finish
00428     while (_spi.write(0xFF) == 0);
00429 
00430     _cs = 1;
00431     _spi.write(0xFF);
00432     return 0;
00433 }
00434 
00435 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00436     uint32_t bits = 0;
00437     uint32_t size = 1 + msb - lsb;
00438     for (uint32_t i = 0; i < size; i++) {
00439         uint32_t position = lsb + i;
00440         uint32_t byte = 15 - (position >> 3);
00441         uint32_t bit = position & 0x7;
00442         uint32_t value = (data[byte] >> bit) & 1;
00443         bits |= value << i;
00444     }
00445     return bits;
00446 }
00447 
00448 uint32_t SDFileSystem::_sd_sectors() {
00449     uint32_t c_size, c_size_mult, read_bl_len;
00450     uint32_t block_len, mult, blocknr, capacity;
00451     uint32_t hc_c_size;
00452     uint32_t blocks;
00453 
00454     // CMD9, Response R2 (R1 byte + 16-byte block read)
00455     if (_cmdx(9, 0) != 0) {
00456         debug("Didn't get a response from the disk\n");
00457         return 0;
00458     }
00459 
00460     uint8_t csd[16];
00461     if (_read(csd, 16) != 0) {
00462         debug("Couldn't read csd response from disk\n");
00463         return 0;
00464     }
00465 
00466     // csd_structure : csd[127:126]
00467     // c_size        : csd[73:62]
00468     // c_size_mult   : csd[49:47]
00469     // read_bl_len   : csd[83:80] - the *maximum* read block length
00470 
00471     int csd_structure = ext_bits(csd, 127, 126);
00472 
00473     switch (csd_structure) {
00474         case 0:
00475             cdv = 512;
00476             c_size = ext_bits(csd, 73, 62);
00477             c_size_mult = ext_bits(csd, 49, 47);
00478             read_bl_len = ext_bits(csd, 83, 80);
00479 
00480             block_len = 1 << read_bl_len;
00481             mult = 1 << (c_size_mult + 2);
00482             blocknr = (c_size + 1) * mult;
00483             capacity = blocknr * block_len;
00484             blocks = capacity / 512;
00485             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00486             break;
00487 
00488         case 1:
00489             cdv = 1;
00490             hc_c_size = ext_bits(csd, 63, 48);
00491             blocks = (hc_c_size+1)*1024;
00492             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);
00493             break;
00494 
00495         default:
00496             debug("CSD struct unsupported\r\n");
00497             return 0;
00498     };
00499     return blocks;
00500 }