SDFileSystem.cpp

00001 /* mbed Microcontroller Library - SDFileSystem
00002  * Copyright (c) 2008-2009, sford
00003  */
00004 
00005 // VERY DRAFT CODE! Needs serious rework/refactoring
00006 
00007 /* Introduction
00008  * ------------
00009  * SD and MMC cards support a number of interfaces, but common to them all
00010  * is one based on SPI. This is the one I'm implmenting because it means
00011  * it is much more portable even though not so performant, and we already
00012  * have the mbed SPI Interface!
00013  *
00014  * The main reference I'm using is Chapter 7, "SPI Mode" of:
00015  *  http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
00016  *
00017  * SPI Startup
00018  * -----------
00019  * The SD card powers up in SD mode. The SPI interface mode is selected by
00020  * asserting CS low and sending the reset command (CMD0). The card will
00021  * respond with a (R1) response.
00022  *
00023  * CMD8 is optionally sent to determine the voltage range supported, and
00024  * indirectly determine whether it is a version 1.x SD/non-SD card or
00025  * version 2.x. I'll just ignore this for now.
00026  *
00027  * ACMD41 is repeatedly issued to initialise the card, until "in idle"
00028  * (bit 0) of the R1 response goes to '0', indicating it is initialised.
00029  *
00030  * You should also indicate whether the host supports High Capicity cards,
00031  * and check whether the card is high capacity - i'll also ignore this
00032  *
00033  * SPI Protocol
00034  * ------------
00035  * The SD SPI protocol is based on transactions made up of 8-bit words, with
00036  * the host starting every bus transaction by asserting the CS signal low. The
00037  * card always responds to commands, data blocks and errors.
00038  *
00039  * The protocol supports a CRC, but by default it is off (except for the
00040  * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
00041  * I'll leave the CRC off I think!
00042  *
00043  * Standard capacity cards have variable data block sizes, whereas High
00044  * Capacity cards fix the size of data block to 512 bytes. I'll therefore
00045  * just always use the Standard Capacity cards with a block size of 512 bytes.
00046  * This is set with CMD16.
00047  *
00048  * You can read and write single blocks (CMD17, CMD25) or multiple blocks
00049  * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
00050  * the card gets a read command, it responds with a response token, and then
00051  * a data token or an error.
00052  *
00053  * SPI Command Format
00054  * ------------------
00055  * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
00056  *
00057  * +---------------+------------+------------+-----------+----------+--------------+
00058  * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
00059  * +---------------+------------+------------+-----------+----------+--------------+
00060  *
00061  * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
00062  *
00063  * All Application Specific commands shall be preceded with APP_CMD (CMD55).
00064  *
00065  * SPI Response Format
00066  * -------------------
00067  * The main response format (R1) is a status byte (normally zero). Key flags:
00068  *  idle - 1 if the card is in an idle state/initialising
00069  *  cmd  - 1 if an illegal command code was detected
00070  *
00071  *    +-------------------------------------------------+
00072  * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
00073  *    +-------------------------------------------------+
00074  *
00075  * R1b is the same, except it is followed by a busy signal (zeros) until
00076  * the first non-zero byte when it is ready again.
00077  *
00078  * Data Response Token
00079  * -------------------
00080  * Every data block written to the card is acknowledged by a byte
00081  * response token
00082  *
00083  * +----------------------+
00084  * | xxx | 0 | status | 1 |
00085  * +----------------------+
00086  *              010 - OK!
00087  *              101 - CRC Error
00088  *              110 - Write Error
00089  *
00090  * Single Block Read and Write
00091  * ---------------------------
00092  *
00093  * Block transfers have a byte header, followed by the data, followed
00094  * by a 16-bit CRC. In our case, the data will always be 512 bytes.
00095  *
00096  * +------+---------+---------+- -  - -+---------+-----------+----------+
00097  * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
00098  * +------+---------+---------+- -  - -+---------+-----------+----------+
00099  */
00100 
00101 #include "SDFileSystem.h"
00102 
00103 #define SD_COMMAND_TIMEOUT 500000
00104 
00105 SDFileSystem::SDFileSystem(PinName mosi, PinName miso, PinName sclk, PinName cs, const char* name) :
00106         FATFileSystem(name), _spi(mosi, miso, sclk), _cs(cs) {
00107     _cs = 1;
00108 }
00109 
00110 #define R1_IDLE_STATE           (1 << 0)
00111 #define R1_ERASE_RESET          (1 << 1)
00112 #define R1_ILLEGAL_COMMAND      (1 << 2)
00113 #define R1_COM_CRC_ERROR        (1 << 3)
00114 #define R1_ERASE_SEQUENCE_ERROR (1 << 4)
00115 #define R1_ADDRESS_ERROR        (1 << 5)
00116 #define R1_PARAMETER_ERROR      (1 << 6)
00117 
00118 // Types
00119 //  - v1.x Standard Capacity
00120 //  - v2.x Standard Capacity
00121 //  - v2.x High Capacity
00122 //  - Not recognised as an SD Card
00123 
00124 #define SDCARD_FAIL 0
00125 #define SDCARD_V1   1
00126 #define SDCARD_V2   2
00127 #define SDCARD_V2HC 3
00128 
00129 int SDFileSystem::initialise_card() {
00130     fprintf(stderr, "\r\ninitialise_card\r\n");
00131     // Set to 100kHz for initialisation, and clock card with cs = 1
00132     _spi.frequency(100000);
00133     _cs = 1;
00134     for (int i=0; i<16; i++) {
00135         _spi.write(0xFF);
00136     }
00137 
00138     // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
00139     if (_cmd(0, 0) != R1_IDLE_STATE) {
00140         fprintf(stderr, "No disk, or could not put SD card in to SPI idle state\n");
00141         return SDCARD_FAIL;
00142     }
00143 
00144     // send CMD8 to determine whther it is ver 2.x
00145     int r = _cmd8();
00146     if (r == R1_IDLE_STATE) {
00147         return initialise_card_v2();
00148     } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
00149         return initialise_card_v1();
00150     } else {
00151         fprintf(stderr, "Not in idle state after sending CMD8 (not an SD card?)\n");
00152         return SDCARD_FAIL;
00153     }
00154 }
00155 
00156 int SDFileSystem::initialise_card_v1() {
00157     for (int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00158         _cmd(55, 0);
00159         if (_cmd(41, 0) == 0) {
00160             return SDCARD_V1;
00161         }
00162     }
00163 
00164     fprintf(stderr, "Timeout waiting for v1.x card\n");
00165     return SDCARD_FAIL;
00166 }
00167 
00168 int SDFileSystem::initialise_card_v2() {
00169     fprintf(stderr, "\r\ninitialise_card_v2\r\n");
00170     for (int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00171         _cmd(55, 0);
00172 //        if(_cmd(41, 0) == 0) {
00173         if (_cmd41() == 0) {
00174             fprintf(stderr, "\r\ncmd41 returns idle - now initialised. Send cmd58\r\n");
00175             _cmd58();
00176             return SDCARD_V2;
00177         }
00178     }
00179 
00180     fprintf(stderr, "Timeout waiting for v2.x card\r\n");
00181     return SDCARD_FAIL;
00182 }
00183 
00184 int SDFileSystem::disk_initialize() {
00185 
00186     int i = initialise_card();
00187     printf("init card = %d\r\n", i);
00188 //    printf("OK\n");
00189 
00190     _sectors = _sd_sectors();
00191 
00192     // Set block length to 512 (CMD16)
00193     if (_cmd(16, 512) != 0) {
00194         fprintf(stderr, "Set 512-byte block timed out\r\n");
00195         return 1;
00196     }
00197 
00198     _spi.frequency(1000000); // Set to 1MHz for data transfer
00199     return 0;
00200 }
00201 
00202 int SDFileSystem::disk_write(const char *buffer, int block_number) {
00203     // set write address for single block (CMD24)
00204     if (_cmd(24, block_number * 512) != 0) {
00205         return 1;
00206     }
00207 
00208     // send the data block
00209     _write(buffer, 512);
00210     return 0;
00211 }
00212 
00213 int SDFileSystem::disk_read(char *buffer, int block_number) {
00214     // set read address for single block (CMD17)
00215     if (_cmd(17, block_number * 512) != 0) {
00216         return 1;
00217     }
00218 
00219     // receive the data
00220     _read(buffer, 512);
00221     return 0;
00222 }
00223 
00224 int SDFileSystem::disk_status() {
00225     return 0;
00226 }
00227 int SDFileSystem::disk_sync() {
00228     return 0;
00229 }
00230 int SDFileSystem::disk_sectors() {
00231     return _sectors;
00232 }
00233 
00234 // PRIVATE FUNCTIONS
00235 
00236 int SDFileSystem::_cmd(int cmd, int arg) {
00237     _cs = 0;
00238 
00239     // send a command
00240     _spi.write(0x40 | cmd);
00241     _spi.write(arg >> 24);
00242     _spi.write(arg >> 16);
00243     _spi.write(arg >> 8);
00244     _spi.write(arg >> 0);
00245     _spi.write(0x95);
00246 
00247     // wait for the repsonse (response[7] == 0)
00248     for (int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00249         int response = _spi.write(0xFF);
00250         if (!(response & 0x80)) {
00251             _cs = 1;
00252             _spi.write(0xFF);
00253             return response;
00254         }
00255     }
00256     _cs = 1;
00257     _spi.write(0xFF);
00258     return -1; // timeout
00259 }
00260 int SDFileSystem::_cmdx(int cmd, int arg) {
00261     _cs = 0;
00262 
00263     // send a command
00264     _spi.write(0x40 | cmd);
00265     _spi.write(arg >> 24);
00266     _spi.write(arg >> 16);
00267     _spi.write(arg >> 8);
00268     _spi.write(arg >> 0);
00269     _spi.write(0x95);
00270 
00271     // wait for the repsonse (response[7] == 0)
00272     for (int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00273         int response = _spi.write(0xFF);
00274         if (!(response & 0x80)) {
00275             return response;
00276         }
00277     }
00278     _cs = 1;
00279     _spi.write(0xFF);
00280     return -1; // timeout
00281 }
00282 
00283 int SDFileSystem::_cmd41() {
00284     fprintf(stderr, "Issuing cmd41\r\n");
00285 
00286     _cs = 0;
00287     int arg = 0;
00288 
00289     // send a command
00290     _spi.write(0x40 | 41);
00291     _spi.write(arg >> 24);
00292     _spi.write(arg >> 16);
00293     _spi.write(arg >> 8);
00294     _spi.write(arg >> 0);
00295     _spi.write(0x95);
00296 
00297     union
00298     {
00299      unsigned int v; // register value
00300      struct CSD_REGISTER f; // register fields
00301     } csd;
00302        
00303     int i;
00304     for (i=0; i<SD_COMMAND_TIMEOUT; i++) {
00305         int response = _spi.write(0xFF);
00306         fprintf(stderr, "cmd41 response=0x%08X\r\n", response);
00307         if (!(response & 0x80)) {
00308             csd.v = _spi.write(0xFF) << 24;
00309             csd.v |= _spi.write(0xFF) << 16;
00310             csd.v |= _spi.write(0xFF) << 8;
00311             csd.v |= _spi.write(0xFF) << 0;
00312 //            _spi.write(0xFF);
00313             
00314            fprintf(stderr, "cmd41 ocr=0x%08X\r\n", csd);
00315 
00316             int test = csd.v;
00317             if (test & (1UL << 31))
00318                 fprintf(stderr, "Bit 31 = ON - Therefore - Card Powered up csd=0x%08X\r\n", csd);
00319 
00320             // card_power_up_http://www.cs.cf.ac.uk/Dave/C/node13.html
00321 //            if (csd_reg->card_power_up_status == 1) {
00322             if (csd.f.card_power_up_status == 1) {            
00323                 fprintf(stderr, "Card Powered up\r\n");
00324 
00325                 if (csd.f.card_capacity_status == 1) {
00326                     fprintf(stderr, "High Capacity Card\r\n");
00327                 }
00328 
00329                 _cs = 1;
00330                 _spi.write(0xFF);
00331                 return 0;
00332             }
00333         }
00334     }
00335     _cs = 1;
00336     _spi.write(0xFF);
00337     fprintf(stderr, "cmd41 timeout - exit with -1 i=%d, csd=0x%08X\r\n", i, csd);
00338     return -1; // timeout
00339 }
00340 
00341 int SDFileSystem::_cmd58() {
00342     _cs = 0;
00343     int arg = 0;
00344 
00345     // send a command
00346     _spi.write(0x40 | 58);
00347     _spi.write(arg >> 24);
00348     _spi.write(arg >> 16);
00349     _spi.write(arg >> 8);
00350     _spi.write(arg >> 0);
00351     _spi.write(0x95);
00352 
00353     // wait for the repsonse (response[7] == 0)
00354     for (int i=0; i<SD_COMMAND_TIMEOUT; i++) {
00355         int response = _spi.write(0xFF);
00356         if (!(response & 0x80)) {
00357             int ocr = _spi.write(0xFF) << 24;
00358             ocr |= _spi.write(0xFF) << 16;
00359             ocr |= _spi.write(0xFF) << 8;
00360             ocr |= _spi.write(0xFF) << 0;
00361 //            printf("OCR = 0x%08X\n", ocr);
00362             _cs = 1;
00363             _spi.write(0xFF);
00364             return response;
00365         }
00366     }
00367     _cs = 1;
00368     _spi.write(0xFF);
00369     return -1; // timeout
00370 }
00371 
00372 int SDFileSystem::_cmd8() {
00373     fprintf(stderr, "Issuing cmd8\r\n");
00374     _cs = 0;
00375 
00376     // send a command
00377     _spi.write(0x40 | 8); // CMD8
00378     _spi.write(0x00);     // reserved
00379     _spi.write(0x00);     // reserved
00380     _spi.write(0x01);     // 3.3v
00381     _spi.write(0xAA);     // check pattern
00382     _spi.write(0x87);     // crc
00383 
00384     // wait for the repsonse (response[7] == 0)
00385     for (int i=0; i<SD_COMMAND_TIMEOUT * 1000; i++) {
00386         char response[5];
00387         response[0] = _spi.write(0xFF);
00388         if (!(response[0] & 0x80)) {
00389             for (int j=1; j<5; j++) {
00390                 response[i] = _spi.write(0xFF);
00391                 fprintf(stderr, " %x,", response[i]);
00392             }
00393             fprintf(stderr, "\r\n");
00394             _cs = 1;
00395             _spi.write(0xFF);
00396             return response[0];
00397         }
00398     }
00399     _cs = 1;
00400     _spi.write(0xFF);
00401     return -1; // timeout
00402 }
00403 
00404 int SDFileSystem::_read(char *buffer, int length) {
00405     _cs = 0;
00406 
00407     // read until start byte (0xFF)
00408     while (_spi.write(0xFF) != 0xFE);
00409 
00410     // read data
00411     for (int i=0; i<length; i++) {
00412         buffer[i] = _spi.write(0xFF);
00413     }
00414     _spi.write(0xFF); // checksum
00415     _spi.write(0xFF);
00416 
00417     _cs = 1;
00418     _spi.write(0xFF);
00419     return 0;
00420 }
00421 
00422 int SDFileSystem::_write(const char *buffer, int length) {
00423     _cs = 0;
00424 
00425     // indicate start of block
00426     _spi.write(0xFE);
00427 
00428     // write the data
00429     for (int i=0; i<length; i++) {
00430         _spi.write(buffer[i]);
00431     }
00432 
00433     // write the checksum
00434     _spi.write(0xFF);
00435     _spi.write(0xFF);
00436 
00437     // check the repsonse token
00438     if ((_spi.write(0xFF) & 0x1F) != 0x05) {
00439         _cs = 1;
00440         _spi.write(0xFF);
00441         return 1;
00442     }
00443 
00444     // wait for write to finish
00445     while (_spi.write(0xFF) == 0);
00446 
00447     _cs = 1;
00448     _spi.write(0xFF);
00449     return 0;
00450 }
00451 
00452 static int ext_bits(char *data, int msb, int lsb) {
00453     int bits = 0;
00454     int size = 1 + msb - lsb;
00455     for (int i=0; i<size; i++) {
00456         int position = lsb + i;
00457         int byte = 15 - (position >> 3);
00458         int bit = position & 0x7;
00459         int value = (data[byte] >> bit) & 1;
00460         bits |= value << i;
00461     }
00462     return bits;
00463 }
00464 
00465 int SDFileSystem::_sd_sectors() {
00466 
00467     // CMD9, Response R2 (R1 byte + 16-byte block read)
00468     if (_cmdx(9, 0) != 0) {
00469         fprintf(stderr, "Didn't get a response from the disk\n");
00470         return 0;
00471     }
00472 
00473     char csd[16];
00474     if (_read(csd, 16) != 0) {
00475         fprintf(stderr, "Couldn't read csd response from disk\n");
00476         return 0;
00477     }
00478 
00479     // csd_structure : csd[127:126]
00480     // c_size        : csd[73:62]
00481     // c_size_mult   : csd[49:47]
00482     // read_bl_len   : csd[83:80] - the *maximum* read block length
00483 
00484     int csd_structure = ext_bits(csd, 127, 126);
00485     int c_size = ext_bits(csd, 73, 62);
00486     int c_size_mult = ext_bits(csd, 49, 47);
00487     int read_bl_len = ext_bits(csd, 83, 80);
00488 
00489 //    printf("CSD_STRUCT = %d\n", csd_structure);
00490 
00491     if (csd_structure != 0) {
00492         fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures\n");
00493         return 0;
00494     }
00495 
00496     // memory capacity = BLOCKNR * BLOCK_LEN
00497     // where
00498     //  BLOCKNR = (C_SIZE+1) * MULT
00499     //  MULT = 2^(C_SIZE_MULT+2) (C_SIZE_MULT < 8)
00500     //  BLOCK_LEN = 2^READ_BL_LEN, (READ_BL_LEN < 12)
00501 
00502     int block_len = 1 << read_bl_len;
00503     int mult = 1 << (c_size_mult + 2);
00504     int blocknr = (c_size + 1) * mult;
00505     int capacity = blocknr * block_len;
00506 
00507     int blocks = capacity / 512;
00508 
00509     return blocks;
00510 }