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 start-up procedure is complicated
00035  * by the requirement to support older SDCards in a backwards compatible
00036  * way with the new higher capacity variants SDHC and SDHC.
00037  *
00038  * The following figures from the specification with associated text describe
00039  * the SPI mode initialisation process:
00040  *  - Figure 7-1: SD Memory Card State Diagram (SPI mode)
00041  *  - Figure 7-2: SPI Mode Initialization Flow
00042  *
00043  * Firstly, a low initial clock should be selected (in the range of 100-
00044  * 400kHZ). After initialisation has been completed, the switch to a
00045  * higher clock speed can be made (e.g. 1MHz). Newer cards will support
00046  * higher speeds than the default _transfer_sck defined here.
00047  * 
00048  * After power up, we need to provide at least 1 msec delay and 74 clock cycles
00049  * before sending any command to an SD Card. Since we get 8 clock cycles with each byte, 
00050  * we can send 10 bytes for a total of 80 clock cycles. 
00051  * The SDCard spec also specifies that CS must be held high during this period.
00052  *
00053  * Next, note the following from the SDCard specification (note to
00054  * Figure 7-1):
00055  *
00056  *  In any of the cases CMD1 is not recommended because it may be difficult for the host
00057  *  to distinguish between MultiMediaCard and SD Memory Card
00058  *
00059  * Hence CMD1 is not used for the initialisation sequence.
00060  *
00061  * The SPI interface mode is selected by asserting CS low and sending the
00062  * reset command (CMD0). The card will respond with a (R1) response.
00063  * In practice many cards initially respond with 0xff or invalid data
00064  * which is ignored. Data is read until a valid response is received
00065  * or the number of re-reads has exceeded a maximim count. If a valid
00066  * response is not received then the CMD0 can be retried. This
00067  * has been found to successfully initialise cards where the SPI master
00068  * (on MCU) has been reset but the SDCard has not, so the first
00069  * CMD0 may be lost.
00070  *
00071  * CMD8 is optionally sent to determine the voltage range supported, and
00072  * indirectly determine whether it is a version 1.x SD/non-SD card or
00073  * version 2.x. I'll just ignore this for now.
00074  *
00075  * ACMD41 is repeatedly issued to initialise the card, until "in idle"
00076  * (bit 0) of the R1 response goes to '0', indicating it is initialised.
00077  *
00078  * You should also indicate whether the host supports High Capicity cards,
00079  * and check whether the card is high capacity - i'll also ignore this
00080  *
00081  * SPI Protocol
00082  * ------------
00083  * The SD SPI protocol is based on transactions made up of 8-bit words, with
00084  * the host starting every bus transaction by asserting the CS signal low. The
00085  * card always responds to commands, data blocks and errors.
00086  *
00087  * The protocol supports a CRC, but by default it is off (except for the
00088  * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
00089  * I'll leave the CRC off I think!
00090  *
00091  * Standard capacity cards have variable data block sizes, whereas High
00092  * Capacity cards fix the size of data block to 512 bytes. I'll therefore
00093  * just always use the Standard Capacity cards with a block size of 512 bytes.
00094  * This is set with CMD16.
00095  *
00096  * You can read and write single blocks (CMD17, CMD25) or multiple blocks
00097  * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
00098  * the card gets a read command, it responds with a response token, and then
00099  * a data token or an error.
00100  *
00101  * SPI Command Format
00102  * ------------------
00103  * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
00104  *
00105  * +---------------+------------+------------+-----------+----------+--------------+
00106  * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
00107  * +---------------+------------+------------+-----------+----------+--------------+
00108  *
00109  * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
00110  *
00111  * All Application Specific commands shall be preceded with APP_CMD (CMD55).
00112  *
00113  * SPI Response Format
00114  * -------------------
00115  * The main response format (R1) is a status byte (normally zero). Key flags:
00116  *  idle - 1 if the card is in an idle state/initialising
00117  *  cmd  - 1 if an illegal command code was detected
00118  *
00119  *    +-------------------------------------------------+
00120  * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
00121  *    +-------------------------------------------------+
00122  *
00123  * R1b is the same, except it is followed by a busy signal (zeros) until
00124  * the first non-zero byte when it is ready again.
00125  *
00126  * Data Response Token
00127  * -------------------
00128  * Every data block written to the card is acknowledged by a byte
00129  * response token
00130  *
00131  * +----------------------+
00132  * | xxx | 0 | status | 1 |
00133  * +----------------------+
00134  *              010 - OK!
00135  *              101 - CRC Error
00136  *              110 - Write Error
00137  *
00138  * Single Block Read and Write
00139  * ---------------------------
00140  *
00141  * Block transfers have a byte header, followed by the data, followed
00142  * by a 16-bit CRC. In our case, the data will always be 512 bytes.
00143  *
00144  * +------+---------+---------+- -  - -+---------+-----------+----------+
00145  * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
00146  * +------+---------+---------+- -  - -+---------+-----------+----------+
00147  *
00148  *
00149  *
00150  */
00151 #include "SDFileSystem.h"
00152 #include "mbed_debug.h"
00153 
00154 #define SD_COMMAND_TIMEOUT                      15/*5000*/
00155 #define SD_CMD0_GO_IDLE_STATE_RETRIES           3
00156 #define SD_CMD0_GO_IDLE_STATE                   0x00
00157 #define SD_DBG                                  0
00158 
00159 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
00160     FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs), _is_initialized(0) {
00161     _cs = 1;
00162 
00163     // Set default frquency, for initialisation and data transfer
00164     _init_sck = 400000;
00165     _transfer_sck = 1000000;
00166 }
00167 
00168 // R1 bits
00169 #define R1_IDLE_STATE           (1 << 0)
00170 #define R1_ERASE_RESET          (1 << 1)
00171 #define R1_ILLEGAL_COMMAND      (1 << 2)
00172 #define R1_COM_CRC_ERROR        (1 << 3)
00173 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00174 #define R1_ADDRESS_ERROR        (1 << 5)
00175 #define R1_PARAMETER_ERROR      (1 << 6)
00176 
00177 // Types
00178 //  - v1.x Standard Capacity
00179 //  - v2.x Standard Capacity
00180 //  - v2.x High Capacity
00181 //  - Not recognised as an SD Card
00182 #define SDCARD_FAIL 0
00183 #define SDCARD_V1   1
00184 #define SDCARD_V2   2
00185 #define SDCARD_V2HC 3
00186 
00187 /* SDFileSystem::_go_idle_state()
00188  *
00189  * ARGUMENTS
00190  *  None
00191  * DETAILS:
00192  *  Put the SDCard into the SPI Mode idle state by sending the CMD0
00193  *  (GO_IDLE_STATE) command. See the notes in the "SPI Startup" section
00194  *  of the comments at the head of this file.
00195  *
00196  * RETURN:
00197  *  -1              an error occured e.g. a valid response was not received.
00198  *  R1_IDLE_STATE   (0x1), the successful response from CMD0.
00199  */
00200 int SDFileSystem::_go_idle_state() {
00201     _spi.lock();
00202     
00203     int cmd_arg = 0;    /* CMD0 argument is just "stuff bits"*/
00204 
00205     /* Resetting the MCU SPI master may not reset the on-board SDCard, in which
00206      * case when MCU power-on occurs the SDCard will resume operations as
00207      * though there was no reset. In this scenario the first CMD0 will
00208      * not be interpretted as a command and get lost. For some cards retrying
00209      * the command overcomes this situation. */
00210     for (int num_retries = 0; num_retries < SD_CMD0_GO_IDLE_STATE_RETRIES; num_retries++) {
00211         
00212         // Set to SCK for initialisation, and clock card with CS high
00213         _cs = 1;
00214         // Initial delay 
00215         wait_us (1000);
00216         // Initial 74 cycles required for few cards, before selecting SPI mode
00217         for (int i = 0; i < 16; i++) {
00218             _spi.write(0xFF);
00219         }
00220         
00221         /* send a CMD0, with /CS asserted low */
00222         _cs = 0;
00223         wait_us (1000);
00224         _spi.write(0x40 | SD_CMD0_GO_IDLE_STATE);
00225         _spi.write(cmd_arg >> 24);
00226         _spi.write(cmd_arg >> 16);
00227         _spi.write(cmd_arg >> 8);
00228         _spi.write(cmd_arg >> 0);
00229         _spi.write(0x95);
00230 
00231         // wait for the response (response[7] == 0)
00232         for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00233             int response = _spi.write(0xFF);
00234             /* Explicitly check for the R1_IDLE_STATE response rather that most significant bit
00235              * being 0 because invalid data can be returned. */
00236             if (response != R1_IDLE_STATE)
00237                 debug_if(SD_DBG, "CMD0 #%d (retry #%d) response: 0x%.2X\n",  i, num_retries, response);
00238             else {
00239                 _cs = 1;
00240                 _spi.write(0xFF);
00241                 _spi.unlock();
00242                 return response;
00243             }
00244             wait_us(1000);    
00245         }
00246     }
00247     _cs = 1;
00248     _spi.write(0xFF);
00249     _spi.unlock();
00250     return -1; // timeout
00251 }
00252 
00253 int SDFileSystem::initialise_card() {
00254     
00255     _spi.lock();
00256     _spi.format(8, 0);
00257     _spi.frequency(_init_sck);
00258     _spi.unlock();
00259     
00260     /* moved within _go_idle_state
00261     _cs = 1;
00262     // Initial delay 
00263     wait_us (1000);
00264     // Initial 74 cycles required for few cards, before selecting SPI mode
00265     for (int i = 0; i < 16; i++) {
00266         _spi.write(0xFF);
00267     }
00268     */
00269   
00270     /* Transition from SD Card mode to SPI mode by sending CMD0 GO_IDLE_STATE command */
00271     if (_go_idle_state() != R1_IDLE_STATE) {
00272         debug_if(SD_DBG, "No disk, or could not put SD card in to SPI idle state\n");
00273         return SDCARD_FAIL;
00274     }   
00275     /* send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00276     if (_cmd(0, 0) != R1_IDLE_STATE) {
00277         debug("No disk, or could not put SD card in to SPI idle state\n");
00278         return SDCARD_FAIL;
00279     }
00280     */
00281 
00282     // send CMD8 to determine whther it is ver 2.x
00283     int r = _cmd8();
00284     if (r == R1_IDLE_STATE) {
00285         return initialise_card_v2();
00286     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00287         return initialise_card_v1();
00288     } else {
00289         debug("Not in idle state after sending CMD8 (not an SD card?)\n");
00290         return SDCARD_FAIL;
00291     }
00292 }
00293 
00294 int SDFileSystem::initialise_card_v1() {
00295     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00296         _cmd(55, 0);
00297         if (_cmd(41, 0) == 0) {
00298             cdv = 512;
00299             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00300             return SDCARD_V1;
00301         }
00302     }
00303 
00304     debug("Timeout waiting for v1.x card\n");
00305     return SDCARD_FAIL;
00306 }
00307 
00308 int SDFileSystem::initialise_card_v2() {
00309     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00310         wait_ms(50);
00311         _cmd58();
00312         _cmd(55, 0);
00313         if (_cmd(41, 0x40000000) == 0) {
00314             _cmd58();
00315             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00316             cdv = 1;
00317             return SDCARD_V2;
00318         }
00319     }
00320 
00321     debug("Timeout waiting for v2.x card\n");
00322     return SDCARD_FAIL;
00323 }
00324 
00325 int SDFileSystem::disk_initialize() {
00326     _is_initialized = initialise_card();
00327     if (_is_initialized == 0) {
00328         debug("Fail to initialize card\n");
00329         return 1;
00330     }
00331     debug_if(SD_DBG, "init card = %d\n", _is_initialized);
00332     _sectors = _sd_sectors();
00333 
00334     // Set block length to 512 (CMD16)
00335     if (_cmd(16, 512) != 0) {
00336         debug("Set 512-byte block timed out\n");
00337         return 1;
00338     }
00339 
00340     // Set SCK for data transfer
00341     _spi.frequency(_transfer_sck);
00342     return 0;
00343 }
00344 
00345 int SDFileSystem::disk_write(const uint8_t* buffer, uint32_t block_number, uint32_t count) {
00346     if (!_is_initialized) {
00347         return -1;
00348     }
00349     
00350     for (uint32_t b = block_number; b < block_number + count; b++) {
00351         // set write address for single block (CMD24)
00352         if (_cmd(24, b * cdv) != 0) {
00353             return 1;
00354         }
00355         
00356         // send the data block
00357         _write(buffer, 512);
00358         buffer += 512;
00359     }
00360     
00361     return 0;
00362 }
00363 
00364 int SDFileSystem::disk_read(uint8_t* buffer, uint32_t block_number, uint32_t count) {
00365     if (!_is_initialized) {
00366         return -1;
00367     }
00368     
00369     for (uint32_t b = block_number; b < block_number + count; b++) {
00370         // set read address for single block (CMD17)
00371         if (_cmd(17, b * cdv) != 0) {
00372             return 1;
00373         }
00374         
00375         // receive the data
00376         _read(buffer, 512);
00377         buffer += 512;
00378     }
00379 
00380     return 0;
00381 }
00382 
00383 int SDFileSystem::disk_status() {
00384     // FATFileSystem::disk_status() returns 0 when initialized
00385     if (_is_initialized) {
00386         return 0;
00387     } else {
00388         return 1;
00389     }
00390 }
00391 
00392 int SDFileSystem::disk_sync() { return 0; }
00393 uint32_t SDFileSystem::disk_sectors() { return _sectors; }
00394 
00395 
00396 // PRIVATE FUNCTIONS
00397 int SDFileSystem::_cmd(int cmd, int arg) {
00398     _cs = 0;
00399 
00400     // send a command
00401     _spi.write(0x40 | cmd);
00402     _spi.write(arg >> 24);
00403     _spi.write(arg >> 16);
00404     _spi.write(arg >> 8);
00405     _spi.write(arg >> 0);
00406     _spi.write(0x95);
00407 
00408     // wait for the repsonse (response[7] == 0)
00409     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00410         int response = _spi.write(0xFF);
00411         if (!(response & 0x80)) {
00412             _cs = 1;
00413             _spi.write(0xFF);
00414             return response;
00415         }
00416     }
00417     _cs = 1;
00418     _spi.write(0xFF);
00419     return -1; // timeout
00420 }
00421 int SDFileSystem::_cmdx(int cmd, int arg) {
00422     _cs = 0;
00423 
00424     // send a command
00425     _spi.write(0x40 | cmd);
00426     _spi.write(arg >> 24);
00427     _spi.write(arg >> 16);
00428     _spi.write(arg >> 8);
00429     _spi.write(arg >> 0);
00430     _spi.write(0x95);
00431 
00432     // wait for the repsonse (response[7] == 0)
00433     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00434         int response = _spi.write(0xFF);
00435         if (!(response & 0x80)) {
00436             return response;
00437         }
00438     }
00439     _cs = 1;
00440     _spi.write(0xFF);
00441     return -1; // timeout
00442 }
00443 
00444 
00445 int SDFileSystem::_cmd58() {
00446     _cs = 0;
00447     int arg = 0;
00448 
00449     // send a command
00450     _spi.write(0x40 | 58);
00451     _spi.write(arg >> 24);
00452     _spi.write(arg >> 16);
00453     _spi.write(arg >> 8);
00454     _spi.write(arg >> 0);
00455     _spi.write(0x95);
00456 
00457     // wait for the repsonse (response[7] == 0)
00458     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00459         int response = _spi.write(0xFF);
00460         if (!(response & 0x80)) {
00461             int ocr = _spi.write(0xFF) << 24;
00462             ocr |= _spi.write(0xFF) << 16;
00463             ocr |= _spi.write(0xFF) << 8;
00464             ocr |= _spi.write(0xFF) << 0;
00465             _cs = 1;
00466             _spi.write(0xFF);
00467             return response;
00468         }
00469     }
00470     _cs = 1;
00471     _spi.write(0xFF);
00472     return -1; // timeout
00473 }
00474 
00475 int SDFileSystem::_cmd8() {
00476     _cs = 0;
00477 
00478     // send a command
00479     _spi.write(0x40 | 8); // CMD8
00480     _spi.write(0x00);     // reserved
00481     _spi.write(0x00);     // reserved
00482     _spi.write(0x01);     // 3.3v
00483     _spi.write(0xAA);     // check pattern
00484     _spi.write(0x87);     // crc
00485 
00486     // wait for the repsonse (response[7] == 0)
00487     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00488         char response[5];
00489         response[0] = _spi.write(0xFF);
00490         if (!(response[0] & 0x80)) {
00491             for (int j = 1; j < 5; j++) {
00492                 response[i] = _spi.write(0xFF);
00493             }
00494             _cs = 1;
00495             _spi.write(0xFF);
00496             return response[0];
00497         }
00498     }
00499     _cs = 1;
00500     _spi.write(0xFF);
00501     return -1; // timeout
00502 }
00503 
00504 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00505     _cs = 0;
00506 
00507     // read until start byte (0xFF)
00508     while (_spi.write(0xFF) != 0xFE);
00509 
00510     // read data
00511     for (uint32_t i = 0; i < length; i++) {
00512         buffer[i] = _spi.write(0xFF);
00513     }
00514     _spi.write(0xFF); // checksum
00515     _spi.write(0xFF);
00516 
00517     _cs = 1;
00518     _spi.write(0xFF);
00519     return 0;
00520 }
00521 
00522 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00523     _cs = 0;
00524 
00525     // indicate start of block
00526     _spi.write(0xFE);
00527 
00528     // write the data
00529     for (uint32_t i = 0; i < length; i++) {
00530         _spi.write(buffer[i]);
00531     }
00532 
00533     // write the checksum
00534     _spi.write(0xFF);
00535     _spi.write(0xFF);
00536 
00537     // check the response token
00538     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00539         _cs = 1;
00540         _spi.write(0xFF);
00541         return 1;
00542     }
00543 
00544     // wait for write to finish
00545     while (_spi.write(0xFF) == 0);
00546 
00547     _cs = 1;
00548     _spi.write(0xFF);
00549     return 0;
00550 }
00551 
00552 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00553     uint32_t bits = 0;
00554     uint32_t size = 1 + msb - lsb;
00555     for (uint32_t i = 0; i < size; i++) {
00556         uint32_t position = lsb + i;
00557         uint32_t byte = 15 - (position >> 3);
00558         uint32_t bit = position & 0x7;
00559         uint32_t value = (data[byte] >> bit) & 1;
00560         bits |= value << i;
00561     }
00562     return bits;
00563 }
00564 
00565 uint32_t SDFileSystem::_sd_sectors() {
00566     uint32_t c_size, c_size_mult, read_bl_len;
00567     uint32_t block_len, mult, blocknr, capacity;
00568     uint32_t hc_c_size;
00569     uint32_t blocks;
00570 
00571     // CMD9, Response R2 (R1 byte + 16-byte block read)
00572     if (_cmdx(9, 0) != 0) {
00573         debug("Didn't get a response from the disk\n");
00574         return 0;
00575     }
00576 
00577     uint8_t csd[16];
00578     if (_read(csd, 16) != 0) {
00579         debug("Couldn't read csd response from disk\n");
00580         return 0;
00581     }
00582 
00583     // csd_structure : csd[127:126]
00584     // c_size        : csd[73:62]
00585     // c_size_mult   : csd[49:47]
00586     // read_bl_len   : csd[83:80] - the *maximum* read block length
00587 
00588     int csd_structure = ext_bits(csd, 127, 126);
00589 
00590     switch (csd_structure) {
00591         case 0:
00592             cdv = 512;
00593             c_size = ext_bits(csd, 73, 62);
00594             c_size_mult = ext_bits(csd, 49, 47);
00595             read_bl_len = ext_bits(csd, 83, 80);
00596 
00597             block_len = 1 << read_bl_len;
00598             mult = 1 << (c_size_mult + 2);
00599             blocknr = (c_size + 1) * mult;
00600             capacity = blocknr * block_len;
00601             blocks = capacity / 512;
00602             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00603             break;
00604 
00605         case 1:
00606             cdv = 1;
00607             hc_c_size = ext_bits(csd, 63, 48);
00608             blocks = (hc_c_size+1)*1024;
00609             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);
00610             break;
00611 
00612         default:
00613             debug("CSD struct unsupported\r\n");
00614             return 0;
00615     };
00616     return blocks;
00617 }