SDFileSystem.cpp

00001 /* mbed SDFileSystem Library, for providing file access to SD cards
00002  * Copyright (c) 2008-2010, sford
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
00020  * THE 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  
00117 #include "SDFileSystem.h"
00118 
00119 #define SD_COMMAND_TIMEOUT 5000
00120 
00121 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
00122   FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
00123       _cs = 1; 
00124 }
00125 
00126 #define R1_IDLE_STATE           (1 << 0)
00127 #define R1_ERASE_RESET          (1 << 1)
00128 #define R1_ILLEGAL_COMMAND      (1 << 2)
00129 #define R1_COM_CRC_ERROR        (1 << 3)
00130 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00131 #define R1_ADDRESS_ERROR        (1 << 5)
00132 #define R1_PARAMETER_ERROR      (1 << 6)
00133 
00134 // Types
00135 //  - v1.x Standard Capacity
00136 //  - v2.x Standard Capacity
00137 //  - v2.x High Capacity
00138 //  - Not recognised as an SD Card
00139 
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         fprintf(stderr, "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         fprintf(stderr, "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             return SDCARD_V1;
00176         }
00177     }
00178 
00179     fprintf(stderr, "Timeout waiting for v1.x card\n");
00180     return SDCARD_FAIL;
00181 }
00182 
00183 int SDFileSystem::initialise_card_v2() {
00184     
00185     for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00186         _cmd(55, 0); 
00187         if(_cmd(41, 0) == 0) { 
00188             _cmd58();
00189             return SDCARD_V2;
00190         }
00191     }
00192 
00193     fprintf(stderr, "Timeout waiting for v2.x card\n");
00194     return SDCARD_FAIL;
00195 }
00196 
00197 int SDFileSystem::disk_initialize() {
00198 
00199     int i = initialise_card();
00200 //    printf("init card = %d\n", i);
00201 //    printf("OK\n");
00202 
00203     _sectors = _sd_sectors();
00204 
00205     // Set block length to 512 (CMD16)
00206     if(_cmd(16, 512) != 0) {
00207         fprintf(stderr, "Set 512-byte block timed out\n");
00208         return 1;
00209     }
00210         
00211     _spi.frequency(1000000); // Set to 1MHz for data transfer
00212     return 0;
00213 }
00214 
00215 int SDFileSystem::disk_write(const char *buffer, int block_number) {
00216     // set write address for single block (CMD24)
00217     if(_cmd(24, block_number * 512) != 0) {
00218         return 1;
00219     }
00220 
00221     // send the data block
00222     _write(buffer, 512);    
00223     return 0;    
00224 }
00225 
00226 int SDFileSystem::disk_read(char *buffer, int block_number) {        
00227     // set read address for single block (CMD17)
00228     if(_cmd(17, block_number * 512) != 0) {
00229         return 1;
00230     }
00231     
00232     // receive the data
00233     _read(buffer, 512);
00234     return 0;
00235 }
00236 
00237 int SDFileSystem::disk_status() { return 0; }
00238 int SDFileSystem::disk_sync() { return 0; }
00239 int SDFileSystem::disk_sectors() { return _sectors; }
00240 
00241 // PRIVATE FUNCTIONS
00242 
00243 int SDFileSystem::_cmd(int cmd, int arg) {
00244     _cs = 0; 
00245 
00246     // send a command
00247     _spi.write(0x40 | cmd);
00248     _spi.write(arg >> 24);
00249     _spi.write(arg >> 16);
00250     _spi.write(arg >> 8);
00251     _spi.write(arg >> 0);
00252     _spi.write(0x95);
00253 
00254     // wait for the repsonse (response[7] == 0)
00255     for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00256         int response = _spi.write(0xFF);
00257         if(!(response & 0x80)) {
00258             _cs = 1;
00259             _spi.write(0xFF);
00260             return response;
00261         }
00262     }
00263     _cs = 1;
00264     _spi.write(0xFF);
00265     return -1; // timeout
00266 }
00267 int SDFileSystem::_cmdx(int cmd, int arg) {
00268     _cs = 0; 
00269 
00270     // send a command
00271     _spi.write(0x40 | cmd);
00272     _spi.write(arg >> 24);
00273     _spi.write(arg >> 16);
00274     _spi.write(arg >> 8);
00275     _spi.write(arg >> 0);
00276     _spi.write(0x95);
00277 
00278     // wait for the repsonse (response[7] == 0)
00279     for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00280         int response = _spi.write(0xFF);
00281         if(!(response & 0x80)) {
00282             return response;
00283         }
00284     }
00285     _cs = 1;
00286     _spi.write(0xFF);
00287     return -1; // timeout
00288 }
00289 
00290 
00291 int SDFileSystem::_cmd58() {
00292     _cs = 0; 
00293     int arg = 0;
00294     
00295     // send a command
00296     _spi.write(0x40 | 58);
00297     _spi.write(arg >> 24);
00298     _spi.write(arg >> 16);
00299     _spi.write(arg >> 8);
00300     _spi.write(arg >> 0);
00301     _spi.write(0x95);
00302 
00303     // wait for the repsonse (response[7] == 0)
00304     for(int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00305         int response = _spi.write(0xFF);
00306         if(!(response & 0x80)) {
00307             int ocr = _spi.write(0xFF) << 24;
00308             ocr |= _spi.write(0xFF) << 16;
00309             ocr |= _spi.write(0xFF) << 8;
00310             ocr |= _spi.write(0xFF) << 0;
00311 //            printf("OCR = 0x%08X\n", ocr);
00312             _cs = 1;
00313             _spi.write(0xFF);
00314             return response;
00315         }
00316     }
00317     _cs = 1;
00318     _spi.write(0xFF);
00319     return -1; // timeout
00320 }
00321 
00322 int SDFileSystem::_cmd8() {
00323     _cs = 0; 
00324     
00325     // send a command
00326     _spi.write(0x40 | 8); // CMD8
00327     _spi.write(0x00);     // reserved
00328     _spi.write(0x00);     // reserved
00329     _spi.write(0x01);     // 3.3v
00330     _spi.write(0xAA);     // check pattern
00331     _spi.write(0x87);     // crc
00332 
00333     // wait for the repsonse (response[7] == 0)
00334     for(int i=0; i<SD_COMMAND_TIMEOUT * 1000; i++) {
00335         char response[5];
00336         response[0] = _spi.write(0xFF);
00337         if(!(response[0] & 0x80)) {
00338                 for(int j=1; j<5; j++) {
00339                     response[i] = _spi.write(0xFF);
00340                 }
00341                 _cs = 1;
00342                 _spi.write(0xFF);
00343                 return response[0];
00344         }
00345     }
00346     _cs = 1;
00347     _spi.write(0xFF);
00348     return -1; // timeout
00349 }
00350 
00351 int SDFileSystem::_read(char *buffer, int length) {
00352     _cs = 0;
00353 
00354     // read until start byte (0xFF)
00355     while(_spi.write(0xFF) != 0xFE);
00356 
00357     // read data
00358     for(int i=0; i<length; i++) {
00359         buffer[i] = _spi.write(0xFF);
00360     }
00361     _spi.write(0xFF); // checksum
00362     _spi.write(0xFF);
00363 
00364     _cs = 1;    
00365     _spi.write(0xFF);
00366     return 0;
00367 }
00368 
00369 int SDFileSystem::_write(const char *buffer, int length) {
00370     _cs = 0;
00371     
00372     // indicate start of block
00373     _spi.write(0xFE);
00374     
00375     // write the data
00376     for(int i=0; i<length; i++) {
00377         _spi.write(buffer[i]);
00378     }
00379     
00380     // write the checksum
00381     _spi.write(0xFF); 
00382     _spi.write(0xFF);
00383 
00384     // check the repsonse token
00385     if((_spi.write(0xFF) & 0x1F) != 0x05) {
00386         _cs = 1;
00387         _spi.write(0xFF);        
00388         return 1;
00389     }
00390 
00391     // wait for write to finish
00392     while(_spi.write(0xFF) == 0);
00393 
00394     _cs = 1; 
00395     _spi.write(0xFF);
00396     return 0;
00397 }
00398 
00399 static int ext_bits(char *data, int msb, int lsb) {
00400     int bits = 0;
00401     int size = 1 + msb - lsb; 
00402     for(int i=0; i<size; i++) {
00403         int position = lsb + i;
00404         int byte = 15 - (position >> 3);
00405         int bit = position & 0x7;
00406         int value = (data[byte] >> bit) & 1;
00407         bits |= value << i;
00408     }
00409     return bits;
00410 }
00411 
00412 int SDFileSystem::_sd_sectors() {
00413 
00414     // CMD9, Response R2 (R1 byte + 16-byte block read)
00415     if(_cmdx(9, 0) != 0) {
00416         fprintf(stderr, "Didn't get a response from the disk\n");
00417         return 0;
00418     }
00419     
00420     char csd[16];    
00421     if(_read(csd, 16) != 0) {
00422         fprintf(stderr, "Couldn't read csd response from disk\n");
00423         return 0;
00424     }
00425 
00426     // csd_structure : csd[127:126]
00427     // c_size        : csd[73:62]
00428     // c_size_mult   : csd[49:47]
00429     // read_bl_len   : csd[83:80] - the *maximum* read block length
00430 
00431     int csd_structure = ext_bits(csd, 127, 126);
00432     int c_size = ext_bits(csd, 73, 62);
00433     int c_size_mult = ext_bits(csd, 49, 47);
00434     int read_bl_len = ext_bits(csd, 83, 80);
00435 
00436 //    printf("CSD_STRUCT = %d\n", csd_structure);
00437     
00438     if(csd_structure != 0) {
00439         fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures\n");
00440         return 0;
00441     }
00442              
00443     // memory capacity = BLOCKNR * BLOCK_LEN
00444     // where
00445     //  BLOCKNR = (C_SIZE+1) * MULT
00446     //  MULT = 2^(C_SIZE_MULT+2) (C_SIZE_MULT < 8)
00447     //  BLOCK_LEN = 2^READ_BL_LEN, (READ_BL_LEN < 12)         
00448                             
00449     int block_len = 1 << read_bl_len;
00450     int mult = 1 << (c_size_mult + 2);
00451     int blocknr = (c_size + 1) * mult;
00452     int capacity = blocknr * block_len;
00453         
00454     int blocks = capacity / 512;
00455         
00456     return blocks;
00457 }