File content as of revision 1:68378811b1e2:

/*-----------------------------------------------------------------------*/
/* Low level disk I/O module skeleton for FatFs     (C)ChaN, 2007        */
/*-----------------------------------------------------------------------*/
/* This is a stub disk I/O module that acts as front end of the existing */
/* disk I/O modules and attach it to FatFs module with common interface. */
/*-----------------------------------------------------------------------*/

#include "diskio.h"
#include "mbed.h"


//******************************************************************************************************************
// MBED SPI/CS Select functions.... Modify for your layout.
//**************************************************************************************

SPI _spi(p5, p6, p7); // mosi, miso, sclk
DigitalOut _cs(p8);

//******************************************************************************************************************
// Low Level Sector Access Function Prototypes('C' Castrated versions of Simon Ford's C++ MBED SDFileSystem class
//******************************************************************************************************************
int _cmd(int cmd, int arg);
int _read(BYTE *buffer, int length);
int _write(BYTE *buffer, int length);
int ext_bits(BYTE *data, int msb, int lsb);
int _sd_sectors();
int _sectors;

#define SD_COMMAND_TIMEOUT 5000


//******************************************************************************************************************
// Sector Access functions for CHAN FatFs 
//******************************************************************************************************************

DRESULT disk_ioctl (
    BYTE drv,        /* Physical drive nmuber (0..) */
    BYTE ctrl,        /* Control code */
    void *buff        /* Buffer to send/receive control data */
)
{
    DRESULT res;

    switch(ctrl)
    {
        case CTRL_SYNC:
             res = RES_OK;
        break;
    
        case GET_SECTOR_SIZE:
              res = RES_OK;
            *(WORD *)buff = 512;
        break;
        
        case GET_SECTOR_COUNT:
            res = RES_OK;
           *(DWORD *)buff = (WORD)_sd_sectors();
        break;
        
        case GET_BLOCK_SIZE:
         res = RES_OK;
          *(DWORD *)buff = 1;
        break;
        
        default:
        res = RES_OK;
        break;
    }
    return res;
}

DSTATUS disk_initialize(BYTE Drive) {

    _spi.frequency(100000); // Set to 100kHz for initialisation
    
    // Initialise the card by clocking it a bit (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) != 0x01) { 
        fprintf(stderr, "Not in idle state\n");
        return STA_NOINIT;
    }
    
    // ACMD41 to give host capacity support (repeat until not busy)
    // ACMD41 is application specific command, so we send APP_CMD (CMD55) beforehand
    for(int i=0;; i++) {
        _cmd(55, 0); 
        int response = _cmd(41, 0);
        if(response == 0) { 
            break;
        } else if(i > SD_COMMAND_TIMEOUT) {
            fprintf(stderr, "Timeout waiting for card\n");
            return STA_NOINIT;
        }    
    }

    _sectors = _sd_sectors();

    // Set block length to 512 (CMD16)
    if(_cmd(16, 512) != 0) {
        fprintf(stderr, "Set block timeout\n");
        return STA_NOINIT;
    }
        
    _spi.frequency(10000000); // Set to 10MHz for data transfer
    return 0;
}

DRESULT disk_write(BYTE Drive,const BYTE * Buffer, DWORD SectorNumber, BYTE SectorCount)
{
    BYTE i;
    
    BYTE * MyBufOut = (BYTE *)Buffer;
    
    for(i=0;i<SectorCount;i++)
    {
        // set write address for single block (CMD24)
        if(_cmd(24, (SectorNumber + i) * 512 ) != 0) {
            return RES_ERROR;
        }

        // send the data block
        _write(MyBufOut, 512);    
        
        MyBufOut+=512;
    }
    return RES_OK;    
}

DRESULT disk_read(BYTE Drive, BYTE * Buffer,DWORD SectorNumber, BYTE SectorCount)
{        
    BYTE i;
    for(i=0;i<SectorCount;i++)
    {
        // set read address for single block (CMD17)
        if(_cmd(17, (SectorNumber+i) * 512) != 0)
        {
            return RES_ERROR;
        }
        // receive the data
        _read(Buffer, 512);
       
        Buffer+=512;
    }
     return RES_OK;
}


DWORD get_fattime(void)
{
    time_t CurrentTimeStamp;
    tm *CurrentLocalTime;
    DWORD FATFSTimeCode;
        
    CurrentTimeStamp = time(NULL);
    CurrentLocalTime = localtime(&CurrentTimeStamp);
        
        //Map the tm struct time into the FatFs time code    
    FATFSTimeCode =  ((CurrentLocalTime->tm_year-80)<<25) | 
                     ((CurrentLocalTime->tm_mon+1)<<21)   | 
                     ((CurrentLocalTime->tm_mday)<<16)    | 
                     ((CurrentLocalTime->tm_hour)<<11)    |
                     ((CurrentLocalTime->tm_min)<<5)     | 
                     ((CurrentLocalTime->tm_sec));

   return FATFSTimeCode;
}

DSTATUS disk_status(BYTE Drive)
{
    return 0;
}

//**************************************************************************************
// Low Level Sector Access Functions (Castrated versions of Simon Fords C++ MBED class
//**************************************************************************************

int _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;
            return response;
        }
    }
    _cs = 1;
    return -1; // timeout
}

int _read(BYTE *buffer, int 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;    
    return 0;
}

int _write(BYTE *buffer, int 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 repsonse token
    if((_spi.write(0xFF) & 0x1F) != 0x05) {
        _cs = 1; 
        return 1;
    }

    // wait for write to finish
    while(_spi.write(0xFF) == 0);

    _cs = 1; 
    return 0;
}

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

int _sd_sectors() {

    // CMD9, Response R2 (R1 byte + 16-byte block read)
    if(_cmd(9, 0) != 0) {
        fprintf(stderr, "Didn't get a response from the disk\n");
        return 0;
    }
    
    BYTE csd[16];    
    if(_read(csd, 16) != 0) {
        fprintf(stderr, "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] 

    int csd_structure = ext_bits(csd, 127, 126);
    int c_size = ext_bits(csd, 73, 62);
    int c_size_mult = ext_bits(csd, 49, 47);
    int read_bl_len = ext_bits(csd, 83, 80);
    
    if(csd_structure != 0) {
        fprintf(stderr, "This disk tastes funny! I only know about type 0 CSD structures");
        return 0;
    }
                            
    int blocks = (c_size + 1) * (1 << (c_size_mult + 2));
    int block_size = 1 << read_bl_len;

    if(block_size != 512) {
        fprintf(stderr, "This disk tastes funny! I only like 512 byte blocks (%d)\r\n",block_size);
        return 0;
    }
    
    return blocks;
}