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 }
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     _spi.frequency(_init_sck);
00152     _cs = 1;
00153     for (int i = 0; i < 16; i++) {
00154         _spi.write(0xFF);
00155     }
00156     
00157     // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00158     if (_cmd(0, 0) != R1_IDLE_STATE) {
00159         debug("No disk, or could not put SD card in to SPI idle state\n");
00160         return SDCARD_FAIL;
00161     }
00162     
00163     // send CMD8 to determine whther it is ver 2.x
00164     int r = _cmd8();
00165     if (r == R1_IDLE_STATE) {
00166         return initialise_card_v2();
00167     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00168         return initialise_card_v1();
00169     } else {
00170         debug("Not in idle state after sending CMD8 (not an SD card?)\n");
00171         return SDCARD_FAIL;
00172     }
00173 }
00174 
00175 int SDFileSystem::initialise_card_v1() {
00176     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00177         _cmd(55, 0);
00178         if (_cmd(41, 0) == 0) {
00179             cdv = 512;
00180             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00181             return SDCARD_V1;
00182         }
00183     }
00184     
00185     debug("Timeout waiting for v1.x card\n");
00186     return SDCARD_FAIL;
00187 }
00188 
00189 int SDFileSystem::initialise_card_v2() {
00190     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00191         wait_ms(50);
00192         _cmd58();
00193         _cmd(55, 0);
00194         if (_cmd(41, 0x40000000) == 0) {
00195             _cmd58();
00196             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00197             cdv = 1;
00198             return SDCARD_V2;
00199         }
00200     }
00201     
00202     debug("Timeout waiting for v2.x card\n");
00203     return SDCARD_FAIL;
00204 }
00205 
00206 int SDFileSystem::disk_initialize() {
00207     _is_initialized = initialise_card();
00208     if (_is_initialized == 0) {
00209         debug("Fail to initialize card\n");
00210         return 1;
00211     }
00212     debug_if(SD_DBG, "init card = %d\n", _is_initialized);
00213     _sectors = _sd_sectors();
00214     
00215     // Set block length to 512 (CMD16)
00216     if (_cmd(16, 512) != 0) {
00217         debug("Set 512-byte block timed out\n");
00218         return 1;
00219     }
00220 
00221     // Set SCK for data transfer
00222     _spi.frequency(_transfer_sck);
00223     return 0;
00224 }
00225 
00226 int SDFileSystem::disk_write(const uint8_t *buffer, uint64_t block_number) {
00227     if (!_is_initialized) {
00228         return -1;
00229     }
00230 
00231     // set write address for single block (CMD24)
00232     if (_cmd(24, block_number * cdv) != 0) {
00233         return 1;
00234     }
00235     
00236     // send the data block
00237     _write(buffer, 512);
00238     return 0;
00239 }
00240 
00241 int SDFileSystem::disk_read(uint8_t *buffer, uint64_t block_number) {
00242     if (!_is_initialized) {
00243         return -1;
00244     }
00245 
00246     // set read address for single block (CMD17)
00247     if (_cmd(17, block_number * cdv) != 0) {
00248         return 1;
00249     }
00250     
00251     // receive the data
00252     _read(buffer, 512);
00253     return 0;
00254 }
00255 
00256 int SDFileSystem::disk_status() {
00257     // FATFileSystem::disk_status() returns 0 when initialized
00258     if (_is_initialized) {
00259         return 0;
00260     } else {
00261         return 1;
00262     }
00263 }
00264 
00265 int SDFileSystem::disk_sync() { return 0; }
00266 uint64_t SDFileSystem::disk_sectors() { return _sectors; }
00267 
00268 
00269 // PRIVATE FUNCTIONS
00270 int SDFileSystem::_cmd(int cmd, int arg) {
00271     _cs = 0;
00272     
00273     // send a command
00274     _spi.write(0x40 | cmd);
00275     _spi.write(arg >> 24);
00276     _spi.write(arg >> 16);
00277     _spi.write(arg >> 8);
00278     _spi.write(arg >> 0);
00279     _spi.write(0x95);
00280     
00281     // wait for the repsonse (response[7] == 0)
00282     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00283         int response = _spi.write(0xFF);
00284         if (!(response & 0x80)) {
00285             _cs = 1;
00286             _spi.write(0xFF);
00287             return response;
00288         }
00289     }
00290     _cs = 1;
00291     _spi.write(0xFF);
00292     return -1; // timeout
00293 }
00294 int SDFileSystem::_cmdx(int cmd, int arg) {
00295     _cs = 0;
00296     
00297     // send a command
00298     _spi.write(0x40 | cmd);
00299     _spi.write(arg >> 24);
00300     _spi.write(arg >> 16);
00301     _spi.write(arg >> 8);
00302     _spi.write(arg >> 0);
00303     _spi.write(0x95);
00304     
00305     // wait for the repsonse (response[7] == 0)
00306     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00307         int response = _spi.write(0xFF);
00308         if (!(response & 0x80)) {
00309             return response;
00310         }
00311     }
00312     _cs = 1;
00313     _spi.write(0xFF);
00314     return -1; // timeout
00315 }
00316 
00317 
00318 int SDFileSystem::_cmd58() {
00319     _cs = 0;
00320     int arg = 0;
00321     
00322     // send a command
00323     _spi.write(0x40 | 58);
00324     _spi.write(arg >> 24);
00325     _spi.write(arg >> 16);
00326     _spi.write(arg >> 8);
00327     _spi.write(arg >> 0);
00328     _spi.write(0x95);
00329     
00330     // wait for the repsonse (response[7] == 0)
00331     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00332         int response = _spi.write(0xFF);
00333         if (!(response & 0x80)) {
00334             int ocr = _spi.write(0xFF) << 24;
00335             ocr |= _spi.write(0xFF) << 16;
00336             ocr |= _spi.write(0xFF) << 8;
00337             ocr |= _spi.write(0xFF) << 0;
00338             _cs = 1;
00339             _spi.write(0xFF);
00340             return response;
00341         }
00342     }
00343     _cs = 1;
00344     _spi.write(0xFF);
00345     return -1; // timeout
00346 }
00347 
00348 int SDFileSystem::_cmd8() {
00349     _cs = 0;
00350     
00351     // send a command
00352     _spi.write(0x40 | 8); // CMD8
00353     _spi.write(0x00);     // reserved
00354     _spi.write(0x00);     // reserved
00355     _spi.write(0x01);     // 3.3v
00356     _spi.write(0xAA);     // check pattern
00357     _spi.write(0x87);     // crc
00358     
00359     // wait for the repsonse (response[7] == 0)
00360     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00361         char response[5];
00362         response[0] = _spi.write(0xFF);
00363         if (!(response[0] & 0x80)) {
00364             for (int j = 1; j < 5; j++) {
00365                 response[i] = _spi.write(0xFF);
00366             }
00367             _cs = 1;
00368             _spi.write(0xFF);
00369             return response[0];
00370         }
00371     }
00372     _cs = 1;
00373     _spi.write(0xFF);
00374     return -1; // timeout
00375 }
00376 
00377 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00378     _cs = 0;
00379     
00380     // read until start byte (0xFF)
00381     while (_spi.write(0xFF) != 0xFE);
00382     
00383     // read data
00384     for (int i = 0; i < length; i++) {
00385         buffer[i] = _spi.write(0xFF);
00386     }
00387     _spi.write(0xFF); // checksum
00388     _spi.write(0xFF);
00389     
00390     _cs = 1;
00391     _spi.write(0xFF);
00392     return 0;
00393 }
00394 
00395 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00396     _cs = 0;
00397     
00398     // indicate start of block
00399     _spi.write(0xFE);
00400     
00401     // write the data
00402     for (int i = 0; i < length; i++) {
00403         _spi.write(buffer[i]);
00404     }
00405     
00406     // write the checksum
00407     _spi.write(0xFF);
00408     _spi.write(0xFF);
00409     
00410     // check the response token
00411     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00412         _cs = 1;
00413         _spi.write(0xFF);
00414         return 1;
00415     }
00416     
00417     // wait for write to finish
00418     while (_spi.write(0xFF) == 0);
00419     
00420     _cs = 1;
00421     _spi.write(0xFF);
00422     return 0;
00423 }
00424 
00425 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00426     uint32_t bits = 0;
00427     uint32_t size = 1 + msb - lsb;
00428     for (int i = 0; i < size; i++) {
00429         uint32_t position = lsb + i;
00430         uint32_t byte = 15 - (position >> 3);
00431         uint32_t bit = position & 0x7;
00432         uint32_t value = (data[byte] >> bit) & 1;
00433         bits |= value << i;
00434     }
00435     return bits;
00436 }
00437 
00438 uint64_t SDFileSystem::_sd_sectors() {
00439     uint32_t c_size, c_size_mult, read_bl_len;
00440     uint32_t block_len, mult, blocknr, capacity;
00441     uint32_t hc_c_size;
00442     uint64_t blocks;
00443     
00444     // CMD9, Response R2 (R1 byte + 16-byte block read)
00445     if (_cmdx(9, 0) != 0) {
00446         debug("Didn't get a response from the disk\n");
00447         return 0;
00448     }
00449     
00450     uint8_t csd[16];
00451     if (_read(csd, 16) != 0) {
00452         debug("Couldn't read csd response from disk\n");
00453         return 0;
00454     }
00455     
00456     // csd_structure : csd[127:126]
00457     // c_size        : csd[73:62]
00458     // c_size_mult   : csd[49:47]
00459     // read_bl_len   : csd[83:80] - the *maximum* read block length
00460     
00461     int csd_structure = ext_bits(csd, 127, 126);
00462     
00463     switch (csd_structure) {
00464         case 0:
00465             cdv = 512;
00466             c_size = ext_bits(csd, 73, 62);
00467             c_size_mult = ext_bits(csd, 49, 47);
00468             read_bl_len = ext_bits(csd, 83, 80);
00469             
00470             block_len = 1 << read_bl_len;
00471             mult = 1 << (c_size_mult + 2);
00472             blocknr = (c_size + 1) * mult;
00473             capacity = blocknr * block_len;
00474             blocks = capacity / 512;
00475             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00476             break;
00477         
00478         case 1:
00479             cdv = 1;
00480             hc_c_size = ext_bits(csd, 63, 48);
00481             blocks = (hc_c_size+1)*1024;
00482             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);
00483             break;
00484         
00485         default:
00486             debug("CSD struct unsupported\r\n");
00487             return 0;
00488     };
00489     return blocks;
00490 }