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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) {
00124     _cs = 1;
00125 }
00126 
00127 #define R1_IDLE_STATE           (1 << 0)
00128 #define R1_ERASE_RESET          (1 << 1)
00129 #define R1_ILLEGAL_COMMAND      (1 << 2)
00130 #define R1_COM_CRC_ERROR        (1 << 3)
00131 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00132 #define R1_ADDRESS_ERROR        (1 << 5)
00133 #define R1_PARAMETER_ERROR      (1 << 6)
00134 
00135 // Types
00136 //  - v1.x Standard Capacity
00137 //  - v2.x Standard Capacity
00138 //  - v2.x High Capacity
00139 //  - Not recognised as an SD Card
00140 #define SDCARD_FAIL 0
00141 #define SDCARD_V1   1
00142 #define SDCARD_V2   2
00143 #define SDCARD_V2HC 3
00144 
00145 int SDFileSystem::initialise_card() {
00146     // Set to 100kHz for initialisation, and clock card with cs = 1
00147     _spi.frequency(100000);
00148     _cs = 1;
00149     for (int i = 0; i < 16; i++) {
00150         _spi.write(0xFF);
00151     }
00152     
00153     // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00154     if (_cmd(0, 0) != R1_IDLE_STATE) {
00155         debug("No disk, or could not put SD card in to SPI idle state\n");
00156         return SDCARD_FAIL;
00157     }
00158     
00159     // send CMD8 to determine whther it is ver 2.x
00160     int r = _cmd8();
00161     if (r == R1_IDLE_STATE) {
00162         return initialise_card_v2();
00163     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00164         return initialise_card_v1();
00165     } else {
00166         debug("Not in idle state after sending CMD8 (not an SD card?)\n");
00167         return SDCARD_FAIL;
00168     }
00169 }
00170 
00171 int SDFileSystem::initialise_card_v1() {
00172     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00173         _cmd(55, 0);
00174         if (_cmd(41, 0) == 0) {
00175             cdv = 512;
00176             debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
00177             return SDCARD_V1;
00178         }
00179     }
00180     
00181     debug("Timeout waiting for v1.x card\n");
00182     return SDCARD_FAIL;
00183 }
00184 
00185 int SDFileSystem::initialise_card_v2() {
00186     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00187         wait_ms(50);
00188         _cmd58();
00189         _cmd(55, 0);
00190         if (_cmd(41, 0x40000000) == 0) {
00191             _cmd58();
00192             debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
00193             cdv = 1;
00194             return SDCARD_V2;
00195         }
00196     }
00197     
00198     debug("Timeout waiting for v2.x card\n");
00199     return SDCARD_FAIL;
00200 }
00201 
00202 int SDFileSystem::disk_initialize() {
00203     int i = initialise_card();
00204     debug_if(SD_DBG, "init card = %d\n", i);
00205     _sectors = _sd_sectors();
00206     
00207     // Set block length to 512 (CMD16)
00208     if (_cmd(16, 512) != 0) {
00209         debug("Set 512-byte block timed out\n");
00210         return 1;
00211     }
00212     
00213     _spi.frequency(1000000); // Set to 1MHz for data transfer
00214     return 0;
00215 }
00216 
00217 int SDFileSystem::disk_write(const uint8_t *buffer, uint64_t block_number) {
00218     // set write address for single block (CMD24)
00219     if (_cmd(24, block_number * cdv) != 0) {
00220         return 1;
00221     }
00222     
00223     // send the data block
00224     _write(buffer, 512);
00225     return 0;
00226 }
00227 
00228 int SDFileSystem::disk_read(uint8_t *buffer, uint64_t block_number) {
00229     // set read address for single block (CMD17)
00230     if (_cmd(17, block_number * cdv) != 0) {
00231         return 1;
00232     }
00233     
00234     // receive the data
00235     _read(buffer, 512);
00236     return 0;
00237 }
00238 
00239 int SDFileSystem::disk_status() { return 0; }
00240 int SDFileSystem::disk_sync() { return 0; }
00241 uint64_t SDFileSystem::disk_sectors() { return _sectors; }
00242 
00243 
00244 // PRIVATE FUNCTIONS
00245 int SDFileSystem::_cmd(int cmd, int arg) {
00246     _cs = 0;
00247     
00248     // send a command
00249     _spi.write(0x40 | cmd);
00250     _spi.write(arg >> 24);
00251     _spi.write(arg >> 16);
00252     _spi.write(arg >> 8);
00253     _spi.write(arg >> 0);
00254     _spi.write(0x95);
00255     
00256     // wait for the repsonse (response[7] == 0)
00257     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00258         int response = _spi.write(0xFF);
00259         if (!(response & 0x80)) {
00260             _cs = 1;
00261             _spi.write(0xFF);
00262             return response;
00263         }
00264     }
00265     _cs = 1;
00266     _spi.write(0xFF);
00267     return -1; // timeout
00268 }
00269 int SDFileSystem::_cmdx(int cmd, int arg) {
00270     _cs = 0;
00271     
00272     // send a command
00273     _spi.write(0x40 | cmd);
00274     _spi.write(arg >> 24);
00275     _spi.write(arg >> 16);
00276     _spi.write(arg >> 8);
00277     _spi.write(arg >> 0);
00278     _spi.write(0x95);
00279     
00280     // wait for the repsonse (response[7] == 0)
00281     for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
00282         int response = _spi.write(0xFF);
00283         if (!(response & 0x80)) {
00284             return response;
00285         }
00286     }
00287     _cs = 1;
00288     _spi.write(0xFF);
00289     return -1; // timeout
00290 }
00291 
00292 
00293 int SDFileSystem::_cmd58() {
00294     _cs = 0;
00295     int arg = 0;
00296     
00297     // send a command
00298     _spi.write(0x40 | 58);
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             int ocr = _spi.write(0xFF) << 24;
00310             ocr |= _spi.write(0xFF) << 16;
00311             ocr |= _spi.write(0xFF) << 8;
00312             ocr |= _spi.write(0xFF) << 0;
00313             _cs = 1;
00314             _spi.write(0xFF);
00315             return response;
00316         }
00317     }
00318     _cs = 1;
00319     _spi.write(0xFF);
00320     return -1; // timeout
00321 }
00322 
00323 int SDFileSystem::_cmd8() {
00324     _cs = 0;
00325     
00326     // send a command
00327     _spi.write(0x40 | 8); // CMD8
00328     _spi.write(0x00);     // reserved
00329     _spi.write(0x00);     // reserved
00330     _spi.write(0x01);     // 3.3v
00331     _spi.write(0xAA);     // check pattern
00332     _spi.write(0x87);     // crc
00333     
00334     // wait for the repsonse (response[7] == 0)
00335     for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
00336         char response[5];
00337         response[0] = _spi.write(0xFF);
00338         if (!(response[0] & 0x80)) {
00339             for (int j = 1; j < 5; j++) {
00340                 response[i] = _spi.write(0xFF);
00341             }
00342             _cs = 1;
00343             _spi.write(0xFF);
00344             return response[0];
00345         }
00346     }
00347     _cs = 1;
00348     _spi.write(0xFF);
00349     return -1; // timeout
00350 }
00351 
00352 int SDFileSystem::_read(uint8_t *buffer, uint32_t length) {
00353     _cs = 0;
00354     
00355     // read until start byte (0xFF)
00356     while (_spi.write(0xFF) != 0xFE);
00357     
00358     // read data
00359     for (int i = 0; i < length; i++) {
00360         buffer[i] = _spi.write(0xFF);
00361     }
00362     _spi.write(0xFF); // checksum
00363     _spi.write(0xFF);
00364     
00365     _cs = 1;
00366     _spi.write(0xFF);
00367     return 0;
00368 }
00369 
00370 int SDFileSystem::_write(const uint8_t*buffer, uint32_t length) {
00371     _cs = 0;
00372     
00373     // indicate start of block
00374     _spi.write(0xFE);
00375     
00376     // write the data
00377     for (int i = 0; i < length; i++) {
00378         _spi.write(buffer[i]);
00379     }
00380     
00381     // write the checksum
00382     _spi.write(0xFF);
00383     _spi.write(0xFF);
00384     
00385     // check the response token
00386     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00387         _cs = 1;
00388         _spi.write(0xFF);
00389         return 1;
00390     }
00391     
00392     // wait for write to finish
00393     while (_spi.write(0xFF) == 0);
00394     
00395     _cs = 1;
00396     _spi.write(0xFF);
00397     return 0;
00398 }
00399 
00400 static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
00401     uint32_t bits = 0;
00402     uint32_t size = 1 + msb - lsb;
00403     for (int i = 0; i < size; i++) {
00404         uint32_t position = lsb + i;
00405         uint32_t byte = 15 - (position >> 3);
00406         uint32_t bit = position & 0x7;
00407         uint32_t value = (data[byte] >> bit) & 1;
00408         bits |= value << i;
00409     }
00410     return bits;
00411 }
00412 
00413 uint64_t SDFileSystem::_sd_sectors() {
00414     uint32_t c_size, c_size_mult, read_bl_len;
00415     uint32_t block_len, mult, blocknr, capacity;
00416     uint32_t hc_c_size;
00417     uint64_t blocks;
00418     
00419     // CMD9, Response R2 (R1 byte + 16-byte block read)
00420     if (_cmdx(9, 0) != 0) {
00421         debug("Didn't get a response from the disk\n");
00422         return 0;
00423     }
00424     
00425     uint8_t csd[16];
00426     if (_read(csd, 16) != 0) {
00427         debug("Couldn't read csd response from disk\n");
00428         return 0;
00429     }
00430     
00431     // csd_structure : csd[127:126]
00432     // c_size        : csd[73:62]
00433     // c_size_mult   : csd[49:47]
00434     // read_bl_len   : csd[83:80] - the *maximum* read block length
00435     
00436     int csd_structure = ext_bits(csd, 127, 126);
00437     
00438     switch (csd_structure) {
00439         case 0:
00440             cdv = 512;
00441             c_size = ext_bits(csd, 73, 62);
00442             c_size_mult = ext_bits(csd, 49, 47);
00443             read_bl_len = ext_bits(csd, 83, 80);
00444             
00445             block_len = 1 << read_bl_len;
00446             mult = 1 << (c_size_mult + 2);
00447             blocknr = (c_size + 1) * mult;
00448             capacity = blocknr * block_len;
00449             blocks = capacity / 512;
00450             debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
00451             break;
00452         
00453         case 1:
00454             cdv = 1;
00455             hc_c_size = ext_bits(csd, 63, 48);
00456             blocks = (hc_c_size+1)*1024;
00457             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);
00458             break;
00459         
00460         default:
00461             debug("CSD struct unsupported\r\n");
00462             return 0;
00463     };
00464     return blocks;
00465 }