File content as of revision 0:9b6d6fa5c401:

#include "mbed.h"
 /* 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] |
 * +------+---------+---------+- -  - -+---------+-----------+----------+
 */


#define SD_COMMAND_TIMEOUT 5000

#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)

#define SDCARD_FAIL 0
#define SDCARD_V1   1
#define SDCARD_V2   2
#define SDCARD_V2HC 3
#define SD_DBG             0

SPI sd(PB_15, PB_14, PB_13); //miso,mosi, sclk
DigitalOut ssel (PB_12);

int cmd(int cmd, int arg);
int cmd8();
int cmd58();
int initialise_card();
int cdv;   
  

void main ()
{
    spi.format(16, 0);
    sd.frequency(2);
    while(1)
     sd.write(0xAA);
     
    initialise_card();
    
}


int cmd(int cmd, int arg) {
    ssel = 0;

    // send a command
    sd.write(0x40 | cmd);
    sd.write(arg >> 24);
    sd.write(arg >> 16);
    sd.write(arg >> 8);
    sd.write(arg >> 0);
    sd.write(0x95);

    // wait for the repsonse (response[7] == 0)
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        int response = sd.write(0xFF);
        if (!(response & 0x80)) {
            ssel= 1;
            sd.write(0xFF);
            return response;
        }
    }
    ssel = 1;
    sd.write(0xFF);
    return -1; // timeout
}


int 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 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 initialise_card() {
    // Set to SCK for initialisation, and clock card with cs = 1
    sd.frequency(100000);
    ssel = 1;
    for (int i = 0; i < 16; i++) {
        sd.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 cmd8() {
    ssel = 0;

    // send a command
    sd.write(0x40 | 8); // CMD8
    sd.write(0x00);     // reserved
    sd.write(0x00);     // reserved
    sd.write(0x01);     // 3.3v
    sd.write(0xAA);     // check pattern
    sd.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] = sd.write(0xFF);
        if (!(response[0] & 0x80)) {
            for (int j = 1; j < 5; j++) {
                response[i] = sd.write(0xFF);
            }
            ssel = 1;
            sd.write(0xFF);
            return response[0];
        }
    }
    ssel = 1;
    sd.write(0xFF);
    return -1; // timeout
}


int cmd58() {
    ssel = 0;
    int arg = 0;

    // send a command
    sd.write(0x40 | 58);
    sd.write(arg >> 24);
    sd.write(arg >> 16);
    sd.write(arg >> 8);
    sd.write(arg >> 0);
    sd.write(0x95);

    // wait for the repsonse (response[7] == 0)
    for (int i = 0; i < SD_COMMAND_TIMEOUT; i++) {
        int response = sd.write(0xFF);
        if (!(response & 0x80)) {
            int ocr = sd.write(0xFF) << 24;
            ocr |= sd.write(0xFF) << 16;
            ocr |= sd.write(0xFF) << 8;
            ocr |= sd.write(0xFF) << 0;
            ssel = 1;
            sd.write(0xFF);
            return response;
        }
    }
    ssel = 1;
    sd.write(0xFF);
    return -1; // timeout
}