File content as of revision 3:dbd7383533e6:

#ifdef OLD
/* mbed Microcontroller Library
 * Copyright (c) 2006-2012 ARM Limited
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
/* Introduction
 * ------------
 * SD and MMC cards support a number of interfaces, but common to them all
 * is one based on SPI. This is the one I'm implmenting because it means
 * it is much more portable even though not so performant, and we already
 * have the mbed SPI Interface!
 *
 * The main reference I'm using is Chapter 7, "SPI Mode" of:
 *  http://www.sdcard.org/developers/tech/sdcard/pls/Simplified_Physical_Layer_Spec.pdf
 *
 * SPI Startup
 * -----------
 * The SD card powers up in SD mode. The SPI interface mode is selected by
 * asserting CS low and sending the reset command (CMD0). The card will
 * respond with a (R1) response.
 *
 * CMD8 is optionally sent to determine the voltage range supported, and
 * indirectly determine whether it is a version 1.x SD/non-SD card or
 * version 2.x. I'll just ignore this for now.
 *
 * ACMD41 is repeatedly issued to initialise the card, until "in idle"
 * (bit 0) of the R1 response goes to '0', indicating it is initialised.
 *
 * You should also indicate whether the host supports High Capicity cards,
 * and check whether the card is high capacity - i'll also ignore this
 *
 * SPI Protocol
 * ------------
 * The SD SPI protocol is based on transactions made up of 8-bit words, with
 * the host starting every bus transaction by asserting the CS signal low. The
 * card always responds to commands, data blocks and errors.
 *
 * The protocol supports a CRC, but by default it is off (except for the
 * first reset CMD0, where the CRC can just be pre-calculated, and CMD8)
 * I'll leave the CRC off I think!
 *
 * Standard capacity cards have variable data block sizes, whereas High
 * Capacity cards fix the size of data block to 512 bytes. I'll therefore
 * just always use the Standard Capacity cards with a block size of 512 bytes.
 * This is set with CMD16.
 *
 * You can read and write single blocks (CMD17, CMD25) or multiple blocks
 * (CMD18, CMD25). For simplicity, I'll just use single block accesses. When
 * the card gets a read command, it responds with a response token, and then
 * a data token or an error.
 *
 * SPI Command Format
 * ------------------
 * Commands are 6-bytes long, containing the command, 32-bit argument, and CRC.
 *
 * +---------------+------------+------------+-----------+----------+--------------+
 * | 01 | cmd[5:0] | arg[31:24] | arg[23:16] | arg[15:8] | arg[7:0] | crc[6:0] | 1 |
 * +---------------+------------+------------+-----------+----------+--------------+
 *
 * As I'm not using CRC, I can fix that byte to what is needed for CMD0 (0x95)
 *
 * All Application Specific commands shall be preceded with APP_CMD (CMD55).
 *
 * SPI Response Format
 * -------------------
 * The main response format (R1) is a status byte (normally zero). Key flags:
 *  idle - 1 if the card is in an idle state/initialising
 *  cmd  - 1 if an illegal command code was detected
 *
 *    +-------------------------------------------------+
 * R1 | 0 | arg | addr | seq | crc | cmd | erase | idle |
 *    +-------------------------------------------------+
 *
 * R1b is the same, except it is followed by a busy signal (zeros) until
 * the first non-zero byte when it is ready again.
 *
 * Data Response Token
 * -------------------
 * Every data block written to the card is acknowledged by a byte
 * response token
 *
 * +----------------------+
 * | xxx | 0 | status | 1 |
 * +----------------------+
 *              010 - OK!
 *              101 - CRC Error
 *              110 - Write Error
 *
 * Single Block Read and Write
 * ---------------------------
 *
 * Block transfers have a byte header, followed by the data, followed
 * by a 16-bit CRC. In our case, the data will always be 512 bytes.
 *
 * +------+---------+---------+- -  - -+---------+-----------+----------+
 * | 0xFE | data[0] | data[1] |        | data[n] | crc[15:8] | crc[7:0] |
 * +------+---------+---------+- -  - -+---------+-----------+----------+
 */
#include "USBMSD_SD.h"
#include "mbed_debug.h"

#define SD_COMMAND_TIMEOUT 5000

#define SD_DBG             0

USBMSD_SD::USBMSD_SD(PinName mosi, PinName miso, PinName sclk, PinName cs) :
    _spi(mosi, miso, sclk), _cs(cs) {
    _cs = 1;
    
    //no init
    _status = 0x01;
    
    connect();
}

#define R1_IDLE_STATE           (1 << 0)
#define R1_ERASE_RESET          (1 << 1)
#define R1_ILLEGAL_COMMAND      (1 << 2)
#define R1_COM_CRC_ERROR        (1 << 3)
#define R1_ERASE_SEQUENCE_ERROR (1 << 4)
#define R1_ADDRESS_ERROR        (1 << 5)
#define R1_PARAMETER_ERROR      (1 << 6)

// Types
//  - v1.x Standard Capacity
//  - v2.x Standard Capacity
//  - v2.x High Capacity
//  - Not recognised as an SD Card
#define SDCARD_FAIL 0
#define SDCARD_V1   1
#define SDCARD_V2   2
#define SDCARD_V2HC 3

int USBMSD_SD::initialise_card() {
    // Set to 100kHz for initialisation, and clock card with cs = 1
    _spi.frequency(100000);
    _cs = 1;
    for (int i = 0; i < 16; i++) {
        _spi.write(0xFF);
    }
    // send CMD0, should return with all zeros except IDLE STATE set (bit 0)
    if (_cmd(0, 0) != R1_IDLE_STATE) {
        debug("No disk, or could not put SD card in to SPI idle state\n");
        return SDCARD_FAIL;
    }
    
    // send CMD8 to determine whther it is ver 2.x
    int r = _cmd8();
    if (r == R1_IDLE_STATE) {
        return initialise_card_v2();
    } else if (r == (R1_IDLE_STATE | R1_ILLEGAL_COMMAND)) {
        return initialise_card_v1();
    } else {
        debug("Not in idle state after sending CMD8 (not an SD card?)\n");
        return SDCARD_FAIL;
    }
}

int USBMSD_SD::initialise_card_v1() {
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        _cmd(55, 0);
        if (_cmd(41, 0) == 0) {
            cdv = 512;
            debug_if(SD_DBG, "\n\rInit: SEDCARD_V1\n\r");
            return SDCARD_V1;
        }
    }
    
    debug("Timeout waiting for v1.x card\n");
    return SDCARD_FAIL;
}

int USBMSD_SD::initialise_card_v2() {
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        wait_ms(50);
        _cmd58();
        _cmd(55, 0);
        if (_cmd(41, 0x40000000) == 0) {
            _cmd58();
            debug_if(SD_DBG, "\n\rInit: SDCARD_V2\n\r");
            cdv = 1;
            return SDCARD_V2;
        }
    }
    
    debug("Timeout waiting for v2.x card\n");
    return SDCARD_FAIL;
}

int USBMSD_SD::disk_initialize() {
    int i = initialise_card();
    debug_if(SD_DBG, "init card = %d\n", i);
    _sectors = _sd_sectors();
    
    // Set block length to 512 (CMD16)
    if (_cmd(16, 512) != 0) {
        debug("Set 512-byte block timed out\n");
        return 1;
    }
    
    _spi.frequency(5000000); // Set to 5MHz for data transfer
    
    // OK
    _status = 0x00;
    
    return 0;
}

int USBMSD_SD::disk_write(const uint8_t *buffer, uint64_t block_number) {
    // set write address for single block (CMD24)
    if (_cmd(24, block_number * cdv) != 0) {
        return 1;
    }
    
    // send the data block
    _write(buffer, 512);
    return 0;
}

int USBMSD_SD::disk_read(uint8_t *buffer, uint64_t block_number) {
    // set read address for single block (CMD17)
    if (_cmd(17, block_number * cdv) != 0) {
        return 1;
    }
    
    // receive the data
    _read(buffer, 512);
    return 0;
}

int USBMSD_SD::disk_status() { return _status; }
int USBMSD_SD::disk_sync() { return 0; }
uint64_t USBMSD_SD::disk_sectors() { return _sectors; }


// PRIVATE FUNCTIONS
int USBMSD_SD::_cmd(int cmd, int arg) {
    _cs = 0;
    
    // send a command
    _spi.write(0x40 | cmd);
    _spi.write(arg >> 24);
    _spi.write(arg >> 16);
    _spi.write(arg >> 8);
    _spi.write(arg >> 0);
    _spi.write(0x95);
    
    // wait for the repsonse (response[7] == 0)
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        int response = _spi.write(0xFF);
        if (!(response & 0x80)) {
            _cs = 1;
            _spi.write(0xFF);
            return response;
        }
    }
    _cs = 1;
    _spi.write(0xFF);
    return -1; // timeout
}
int USBMSD_SD::_cmdx(int cmd, int arg) {
    _cs = 0;
    
    // send a command
    _spi.write(0x40 | cmd);
    _spi.write(arg >> 24);
    _spi.write(arg >> 16);
    _spi.write(arg >> 8);
    _spi.write(arg >> 0);
    _spi.write(0x95);
    
    // wait for the repsonse (response[7] == 0)
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        int response = _spi.write(0xFF);
        if (!(response & 0x80)) {
            return response;
        }
    }
    _cs = 1;
    _spi.write(0xFF);
    return -1; // timeout
}


int USBMSD_SD::_cmd58() {
    _cs = 0;
    int arg = 0;
    
    // send a command
    _spi.write(0x40 | 58);
    _spi.write(arg >> 24);
    _spi.write(arg >> 16);
    _spi.write(arg >> 8);
    _spi.write(arg >> 0);
    _spi.write(0x95);
    
    // wait for the repsonse (response[7] == 0)
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        int response = _spi.write(0xFF);
        if (!(response & 0x80)) {
            int ocr = _spi.write(0xFF) << 24;
            ocr |= _spi.write(0xFF) << 16;
            ocr |= _spi.write(0xFF) << 8;
            ocr |= _spi.write(0xFF) << 0;
            _cs = 1;
            _spi.write(0xFF);
            return response;
        }
    }
    _cs = 1;
    _spi.write(0xFF);
    return -1; // timeout
}

int USBMSD_SD::_cmd8() {
    _cs = 0;
    
    // send a command
    _spi.write(0x40 | 8); // CMD8
    _spi.write(0x00);     // reserved
    _spi.write(0x00);     // reserved
    _spi.write(0x01);     // 3.3v
    _spi.write(0xAA);     // check pattern
    _spi.write(0x87);     // crc
    
    // wait for the repsonse (response[7] == 0)
    for (int i = 0; i < SD_COMMAND_TIMEOUT * 1000; i++) {
        char response[5];
        response[0] = _spi.write(0xFF);
        if (!(response[0] & 0x80)) {
            for (int j = 1; j < 5; j++) {
                response[i] = _spi.write(0xFF);
            }
            _cs = 1;
            _spi.write(0xFF);
            return response[0];
        }
    }
    _cs = 1;
    _spi.write(0xFF);
    return -1; // timeout
}

int USBMSD_SD::_read(uint8_t *buffer, uint32_t length) {
    _cs = 0;
    
    // read until start byte (0xFF)
    while (_spi.write(0xFF) != 0xFE);
    
    // read data
    for (int i = 0; i < length; i++) {
        buffer[i] = _spi.write(0xFF);
    }
    _spi.write(0xFF); // checksum
    _spi.write(0xFF);
    
    _cs = 1;
    _spi.write(0xFF);
    return 0;
}

int USBMSD_SD::_write(const uint8_t*buffer, uint32_t length) {
    _cs = 0;
    
    // indicate start of block
    _spi.write(0xFE);
    
    // write the data
    for (int i = 0; i < length; i++) {
        _spi.write(buffer[i]);
    }
    
    // write the checksum
    _spi.write(0xFF);
    _spi.write(0xFF);
    
    // check the response token
    if ((_spi.write(0xFF) & 0x1F) != 0x05) {
        _cs = 1;
        _spi.write(0xFF);
        return 1;
    }
    
    // wait for write to finish
    while (_spi.write(0xFF) == 0);
    
    _cs = 1;
    _spi.write(0xFF);
    return 0;
}

static uint32_t ext_bits(unsigned char *data, int msb, int lsb) {
    uint32_t bits = 0;
    uint32_t size = 1 + msb - lsb;
    for (int i = 0; i < size; i++) {
        uint32_t position = lsb + i;
        uint32_t byte = 15 - (position >> 3);
        uint32_t bit = position & 0x7;
        uint32_t value = (data[byte] >> bit) & 1;
        bits |= value << i;
    }
    return bits;
}

uint64_t USBMSD_SD::_sd_sectors() {
    uint32_t c_size, c_size_mult, read_bl_len;
    uint32_t block_len, mult, blocknr, capacity;
    uint32_t hc_c_size;
    uint64_t blocks;
    
    // CMD9, Response R2 (R1 byte + 16-byte block read)
    if (_cmdx(9, 0) != 0) {
        debug("Didn't get a response from the disk\n");
        return 0;
    }
    
    uint8_t csd[16];
    if (_read(csd, 16) != 0) {
        debug("Couldn't read csd response from disk\n");
        return 0;
    }
    
    // csd_structure : csd[127:126]
    // c_size        : csd[73:62]
    // c_size_mult   : csd[49:47]
    // read_bl_len   : csd[83:80] - the *maximum* read block length
    
    int csd_structure = ext_bits(csd, 127, 126);
    
    switch (csd_structure) {
        case 0:
            cdv = 512;
            c_size = ext_bits(csd, 73, 62);
            c_size_mult = ext_bits(csd, 49, 47);
            read_bl_len = ext_bits(csd, 83, 80);
            
            block_len = 1 << read_bl_len;
            mult = 1 << (c_size_mult + 2);
            blocknr = (c_size + 1) * mult;
            capacity = blocknr * block_len;
            blocks = capacity / 512;
            debug_if(SD_DBG, "\n\rSDCard\n\rc_size: %d \n\rcapacity: %ld \n\rsectors: %lld\n\r", c_size, capacity, blocks);
            break;
        
        case 1:
            cdv = 1;
            hc_c_size = ext_bits(csd, 63, 48);
            blocks = (hc_c_size+1)*1024;
            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);
            break;
        
        default:
            debug("CSD struct unsupported\r\n");
            return 0;
    };
    return blocks;
}

#endif


#define NEW
#ifdef NEW

#ifdef FOO
You have to inherit from USBMSD and define ALL the following pure virtual functions:
virtual int disk_read(uint8_t * data, uint64_t block): function to read a block
virtual int disk_write(const uint8_t * data, uint64_t block): function to write a block
virtual int disk_initialize(): function to initialize the memory
virtual uint64_t disk_sectors(): return the number of blocks
virtual uint64_t disk_size(): return the memory size
virtual int disk_status(): return the status of the storage chip (0: OK, 1: not initialized, 2: no medium in the drive, 4: write protection)
All functions names are compatible with the fat filesystem library. So you can imagine using your own class with USBMSD and the fat filesystem library in the same program. Just be careful because there are two different parts which will access the sd card. You can do a master/slave system using disk_status().
Once these functions defined, you can call connect() (at the end of the constructor of your class for instance) of USBMSD to connect your mass storage device. connect() will first call disk_status() to test the status of the disk. If disk_status() returns 1 (disk not initialized), then disk_initialize() is called. After this step, connect() will collect information such as the number of blocks and the memory size.
#endif

#include "USBMSD_SD.h"
#include "mbed_debug.h"

#define SD_COMMAND_TIMEOUT 5000
#define SD_DBG             0
#define BLOCKS  16
#define FS  BLOCKS*512

LocalFileSystem local("local"); 

char    s[FS];
int     status = 1;

USBMSD_SD::USBMSD_SD(PinName mosi, PinName miso, PinName sclk, PinName cs) :
    _spi(mosi, miso, sclk), _cs(cs) {
    _cs = 1;
    
    printf("cons\n");
    connect();
}

int USBMSD_SD::disk_initialize() { 

    printf("ini\n");
    status--;
    return 0;
}

int USBMSD_SD::disk_write(const uint8_t *buffer, uint64_t block_number) {

//
// find the correct block and write
//
    int offset;
    int i;
    
    //printf("write\n");
    if (block_number > (BLOCKS -1)) return 1;
    offset = 512 * block_number;   
    for (i = 0; i < 512; i++) {
        s[offset + i] = buffer[i];  
    }
    return 0;
}

int USBMSD_SD::disk_read(uint8_t *buffer, uint64_t block_number) {

    int offset;
    int i;
    
    //printf("read\n");
    if (block_number > (BLOCKS -1)) return 1;
    offset = 512 * block_number;   
    for (i = 0; i < 512; i++) {
        buffer[i] = s[offset + i];  
    }
    return 0;
}

int USBMSD_SD::disk_status() { 
    printf("status\n");
    return status; 
}


int USBMSD_SD::disk_sync() { printf("sync\n"); return 0; }
uint64_t USBMSD_SD::disk_size() { printf("size\n"); return FS;}
uint64_t USBMSD_SD::disk_sectors() { printf("sectors\n"); return BLOCKS; }



#endif