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_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, const char* name) :
00124     FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
00125     _cs.mode(PullUp);
00126     _cs.output();
00127     _cs = 1;
00128 }
00129 
00130 #define R1_IDLE_STATE           (1 << 0)
00131 #define R1_ERASE_RESET          (1 << 1)
00132 #define R1_ILLEGAL_COMMAND      (1 << 2)
00133 #define R1_COM_CRC_ERROR        (1 << 3)
00134 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00135 #define R1_ADDRESS_ERROR        (1 << 5)
00136 #define R1_PARAMETER_ERROR      (1 << 6)
00137 
00138 // Types
00139 #define SDCARD_FAIL 0 //!< v1.x Standard Capacity
00140 #define SDCARD_V1   1 //!< v2.x Standard Capacity
00141 #define SDCARD_V2   2 //!< v2.x High Capacity
00142 #define SDCARD_V2HC 3 //!< Not recognised as an SD Card
00143 
00144 int SDFileSystem::initialise_card() {
00145     // Set to 100kHz for initialisation, and clock card with cs = 1
00146     _spi.frequency(100000);
00147     
00148     _cs.mode(PullUp);
00149     _cs.output();
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 int SDFileSystem::initialise_card_v2() {
00188     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00189         wait_ms(50);
00190         _cmd58();
00191         _cmd(55, 0);
00192         if (_cmd(41, 0x40000000) == 0) {
00193             _cmd58();
00194             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00195             cdv = 1;
00196             return SDCARD_V2;
00197         }
00198     }
00199     
00200     debug("Timeout waiting for v2.x card\n");
00201     return SDCARD_FAIL;
00202 }
00203 
00204 int SDFileSystem::disk_initialize() {
00205     int i = initialise_card();
00206     debug_if(SD_DBG, "init card = %d\n", i);
00207     _sectors = _sd_sectors();
00208     
00209     // Set block length to 512 (CMD16)
00210     if (_cmd(16, 512) != 0) {
00211         debug("Set 512-byte block timed out\n");
00212         return 1;
00213     }
00214     
00215     _spi.frequency(1000000); // Set to 1MHz for data transfer
00216     return 0;
00217 }
00218 
00219 int SDFileSystem::disk_write(const uint8_t *buffer, uint64_t block_number) {
00220     // set write address for single block (CMD24)
00221     if (_cmd(24, block_number * cdv) != 0) {
00222         return 1;
00223     }
00224     
00225     // send the data block
00226     _write(buffer, 512);
00227     return 0;
00228 }
00229 
00230 int SDFileSystem::disk_read(uint8_t *buffer, uint64_t block_number) {
00231     // set read address for single block (CMD17)
00232     if (_cmd(17, block_number * cdv) != 0) {
00233         return 1;
00234     }
00235     
00236     // receive the data
00237     _read(buffer, 512);
00238     return 0;
00239 }
00240 
00241 int SDFileSystem::disk_status() { return 0; }
00242 int SDFileSystem::disk_sync() { return 0; }
00243 uint64_t SDFileSystem::disk_sectors() { return _sectors; }
00244 
00245 
00246 // PRIVATE FUNCTIONS
00247 int SDFileSystem::_cmd(int cmd, int arg) {
00248     _cs = 0;
00249     
00250     // send a command
00251     _spi.write(0x40 | cmd);
00252     _spi.write(arg >> 24);
00253     _spi.write(arg >> 16);
00254     _spi.write(arg >> 8);
00255     _spi.write(arg >> 0);
00256     _spi.write(0x95);
00257     
00258     // wait for the repsonse (response[7] == 0)
00259     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00260         int response = _spi.write(0xFF);
00261         if (!(response & 0x80)) {
00262             _cs = 1;
00263             _spi.write(0xFF);
00264             return response;
00265         }
00266     }
00267     _cs = 1;
00268     _spi.write(0xFF);
00269     return -1; // timeout
00270 }
00271 int SDFileSystem::_cmdx(int cmd, int arg) {
00272     _cs = 0;
00273     
00274     // send a command
00275     _spi.write(0x40 | cmd);
00276     _spi.write(arg >> 24);
00277     _spi.write(arg >> 16);
00278     _spi.write(arg >> 8);
00279     _spi.write(arg >> 0);
00280     _spi.write(0x95);
00281     
00282     // wait for the repsonse (response[7] == 0)
00283     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00284         int response = _spi.write(0xFF);
00285         if (!(response & 0x80)) {
00286             return response;
00287         }
00288     }
00289     _cs = 1;
00290     _spi.write(0xFF);
00291     return -1; // timeout
00292 }
00293 
00294 
00295 int SDFileSystem::_cmd58() {
00296     _cs = 0;
00297     int arg = 0;
00298     
00299     // send a command
00300     _spi.write(0x40 | 58);
00301     _spi.write(arg >> 24);
00302     _spi.write(arg >> 16);
00303     _spi.write(arg >> 8);
00304     _spi.write(arg >> 0);
00305     _spi.write(0x95);
00306     
00307     // wait for the repsonse (response[7] == 0)
00308     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00309         int response = _spi.write(0xFF);
00310         if (!(response & 0x80)) {
00311             int ocr = _spi.write(0xFF) << 24;
00312             ocr |= _spi.write(0xFF) << 16;
00313             ocr |= _spi.write(0xFF) << 8;
00314             ocr |= _spi.write(0xFF) << 0;
00315             _cs = 1;
00316             _spi.write(0xFF);
00317             return response;
00318         }
00319     }
00320     _cs = 1;
00321     _spi.write(0xFF);
00322     return -1; // timeout
00323 }
00324 
00325 int SDFileSystem::_cmd8() {
00326     _cs = 0;
00327     
00328     // send a command
00329     _spi.write(0x40 | 8); // CMD8
00330     _spi.write(0x00);     // reserved
00331     _spi.write(0x00);     // reserved
00332     _spi.write(0x01);     // 3.3v
00333     _spi.write(0xAA);     // check pattern
00334     _spi.write(0x87);     // crc
00335     
00336     // wait for the repsonse (response[7] == 0)
00337     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00338         char response[5];
00339         response[0] = _spi.write(0xFF);
00340         if (!(response[0] & 0x80)) {
00341             for (int j = 1; j < 5; j++) {
00342                 response[i] = _spi.write(0xFF);
00343             }
00344             _cs = 1;
00345             _spi.write(0xFF);
00346             return response[0];
00347         }
00348     }
00349     _cs = 1;
00350     _spi.write(0xFF);
00351     return -1; // timeout
00352 }
00353 
00354 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00355     _cs = 0;
00356     
00357     // read until start byte (0xFF)
00358     while (_spi.write(0xFF) != 0xFE);
00359     
00360     // read data
00361     for (int i = 0; i < length; i++) {
00362         buffer[i] = _spi.write(0xFF);
00363     }
00364     _spi.write(0xFF); // checksum
00365     _spi.write(0xFF);
00366     
00367     _cs = 1;
00368     _spi.write(0xFF);
00369     return 0;
00370 }
00371 
00372 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00373     _cs = 0;
00374     
00375     // indicate start of block
00376     _spi.write(0xFE);
00377     
00378     // write the data
00379     for (int i = 0; i < length; i++) {
00380         _spi.write(buffer[i]);
00381     }
00382     
00383     // write the checksum
00384     _spi.write(0xFF);
00385     _spi.write(0xFF);
00386     
00387     // check the response token
00388     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00389         _cs = 1;
00390         _spi.write(0xFF);
00391         return 1;
00392     }
00393     
00394     // wait for write to finish
00395     while (_spi.write(0xFF) == 0);
00396     
00397     _cs = 1;
00398     _spi.write(0xFF);
00399     return 0;
00400 }
00401 
00402 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00403     uint32_t bits = 0;
00404     uint32_t size = 1 + msb - lsb;
00405     for (int i = 0; i < size; i++) {
00406         uint32_t position = lsb + i;
00407         uint32_t byte = 15 - (position >> 3);
00408         uint32_t bit = position & 0x7;
00409         uint32_t value = (data[byte] >> bit) & 1;
00410         bits |= value << i;
00411     }
00412     return bits;
00413 }
00414 
00415 uint64_t SDFileSystem::_sd_sectors() {
00416     uint32_t c_size, c_size_mult, read_bl_len;
00417     uint32_t block_len, mult, blocknr, capacity;
00418     uint32_t hc_c_size;
00419     uint64_t blocks;
00420     
00421     // CMD9, Response R2 (R1 byte + 16-byte block read)
00422     if (_cmdx(9, 0) != 0) {
00423         debug("Didn't get a response from the disk\n");
00424         return 0;
00425     }
00426     
00427     uint8_t csd[16];
00428     if (_read(csd, 16) != 0) {
00429         debug("Couldn't read csd response from disk\n");
00430         return 0;
00431     }
00432     
00433     // csd_structure : csd[127:126]
00434     // c_size        : csd[73:62]
00435     // c_size_mult   : csd[49:47]
00436     // read_bl_len   : csd[83:80] - the *maximum* read block length
00437     
00438     int csd_structure = ext_bits(csd, 127, 126);
00439     
00440     switch (csd_structure) {
00441         case 0:
00442             cdv = 512;
00443             c_size = ext_bits(csd, 73, 62);
00444             c_size_mult = ext_bits(csd, 49, 47);
00445             read_bl_len = ext_bits(csd, 83, 80);
00446             
00447             block_len = 1 << read_bl_len;
00448             mult = 1 << (c_size_mult + 2);
00449             blocknr = (c_size + 1) * mult;
00450             capacity = blocknr * block_len;
00451             blocks = capacity / 512;
00452             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00453             break;
00454         
00455         case 1:
00456             cdv = 1;
00457             hc_c_size = ext_bits(csd, 63, 48);
00458             blocks = (hc_c_size+1)*1024;
00459             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);
00460             break;
00461         
00462         default:
00463             debug("CSD struct unsupported\r\n");
00464             return 0;
00465     };
00466     return blocks;
00467 }