mmc_spi.c

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//###########################################################
// File: mmc_spi.c
//
// Read-/Writeroutines for MMC MultiMedia cards and
// SD SecureDigital cards in SPI mode.
//
// This will work only for MMC cards with 512 bytes block length !
// This will work only for MMC cards with a partition table !
//
//
//#########################################################################
// Last change: 21.05.2004
//#########################################################################
// [e-mail]
// http://home.t-online.de/home/holger.klabunde/homepage.htm
//#########################################################################
// Compiler: AVR-GCC 3.2
//#########################################################################

#include <io.h>

#include "dos.h"

#ifdef MMC_CARD_SPI

//######################################################
unsigned char MMCCommand(unsigned char command, unsigned long adress)
//######################################################
{

 SPI_WRITE(0xFF); 			 //Dummy write
 SPI_WRITE(command);
 SPI_WRITE((unsigned char)(adress>>24)); //MSB of adress
 SPI_WRITE((unsigned char)(adress>>16));
 SPI_WRITE((unsigned char)(adress>>8));
 SPI_WRITE((unsigned char)adress);       //LSB of adress
 SPI_WRITE(0xFF); 			 //dummy checksum
 SPI_WRITE(0xFF); 			 //16 bit response
 SPI_WRITE(0xFF);

 return SPDR;      			 // only last 8 bits used
}

//######################################################
unsigned char MMCReadSector(unsigned long sector, unsigned char *buf)
//######################################################
{
 unsigned int i;
 unsigned char *p;
 unsigned long startadr;
 
 if(sector>=maxsect) return 1; //sectornumber too big

 p=buf; //using a pointer is much faster than indexing buf[i]
 
 MMC_CS_OFF();

//calculate startadress of the sector
 startadr=sector * (unsigned long)BYTE_PER_SEC;

 MMCCommand(MMC_READ_BLOCK,startadr);

 do
  {
   SPI_WRITE(0xFF);
  }while(SPDR!=0xFE); // wait for card response
  
 
 for(i=0; i<BYTE_PER_SEC; i++)
  {
   SPI_WRITE(0xFF); // shift out a byte into SPDR
   *p++=SPDR;       // store byte in buffer
  } 

 SPI_WRITE(0xFF); // 16 bit crc follows data
 SPI_WRITE(0xFF);

 MMC_CS_ON();

 return 0;
}

#ifdef DOS_WRITE
//######################################################
unsigned char MMCWriteSector(unsigned long sector, unsigned char *buf)
//######################################################
{
 unsigned int i;
 unsigned char *p, by;
 unsigned long startadr;

 if(sector>=maxsect) return 1; //sectornumber too big
 
 p=buf; //using a pointer is much faster than indexing buf[i]

 MMC_CS_OFF();

//calculate startadress
 startadr=sector * (unsigned long)BYTE_PER_SEC;

 MMCCommand(MMC_WRITE_BLOCK,startadr);

 SPI_WRITE(0xFF); // do we need this TWO dummy writes ?
 SPI_WRITE(0xFF);

 SPI_WRITE(0xFE); // start block token

 for(i=0; i<BYTE_PER_SEC; i++)
  {
   SPI_WRITE(*p++);
  }

 SPI_WRITE(0xFF); // 16 bit crc follows data
 SPI_WRITE(0xFF);

 SPI_WRITE(0xFF); // read response
 by=SPDR & 0x1F;
 if(by != 0x05)   // data block accepted ?
  {
   MMC_CS_ON();
   return 1;
  }

 do
  {
   SPI_WRITE(0xFF);
  }while(SPDR !=0xFF); // wait til busy is gone

 MMC_CS_ON();

 return 0;
}
#endif //DOS_WRITE

//######################################################
unsigned char MMCIdentify(void)
//######################################################
{
 unsigned char by;
 unsigned int i;
 unsigned int c_size, c_size_mult, read_bl_len;
 unsigned long drive_size;

//Init SPI with a very slow transfer rate first !

//SPCR SPI Controlregister
// SPIE=0; //No SPI Interrupt
// SPE=1;  //SPI Enable
// DORD=0; //Send MSB first
// MSTR=1; //I am the master !
// CPOL=0; //SCK low if IDLE
// CPHA=0; //SPI Mode 0
// SPR1=1; //SPI Clock = f/128 = 125kHz @16MHz Clock
// SPR0=1; //or f/64 if SPI2X = 1 in SPSR register
 SPCR=0x53;

//SPSR SPI Statusregister
// SPI2X=1; //Double speed for SPI = 250kHz @16MHz Clock
// SPSR=0x01;
 SPSR=0x00;

 for(i=0; i<10; i++) SPI_WRITE(0xFF); // give min 74 clock pulses before
                                      // sending commands
 
 MMC_CS_OFF();

//send CMD0 for RESET
 SPI_WRITE(MMC_RESET); //command code CMD0
 SPI_WRITE(0x00);
 SPI_WRITE(0x00);
 SPI_WRITE(0x00);
 SPI_WRITE(0x00);
 SPI_WRITE(0x95); // CMD0 needs a checksum !
 SPI_WRITE(0xFF); // get 16 bit response high
 SPI_WRITE(0xFF); // get 16 bit response low
 by=SPDR;         // only last 8 bits neccessary

//repeat CMD1 til result=0
 do
  {
   by=MMCCommand(MMC_INIT,0);
  }while(by!=0);

//read CID
// MMCCommand(MMC_READ_CID,0); // nothing really interesting here

//read CSD Card Specific Data
 MMCCommand(MMC_READ_CSD,0);
 SPI_WRITE(0xFF); // ignore response 0xFE

 for(i=0; i<16; i++) //CSD has 128 bits -> 16 bytes
  {
   SPI_WRITE(0xFF);
   by=SPDR;
//   ShowHex(by);
   iob[i]=by;
  }

 SPI_WRITE(0xFF); // 16 bit crc follows data
 SPI_WRITE(0xFF);

 c_size=iob[6] & 0x03; //bits 1..0
 c_size<<=10;
 c_size+=(unsigned int)iob[7]<<2;
 c_size+=iob[8]>>6;

 by= iob[5] & 0x0F;
 read_bl_len=1;
 read_bl_len<<=by;

 by=iob[9] & 0x03;
 by<<=1;
 by+=iob[10] >> 7;
 
 c_size_mult=1;
 c_size_mult<<=(2+by);

 drive_size=(unsigned long)(c_size+1) * (unsigned long)c_size_mult * (unsigned long)read_bl_len;
 maxsect= drive_size / BYTE_PER_SEC;

 MMC_CS_ON();

//switch to high speed SPI
// SPR1=0; //SPI Clock = f/4 = 4MHz @16MHz Clock
// SPR0=0; //or f/2 if SPI2X = 1 in SPSR register
 SPCR=0x50;

//SPSR SPI Statusregister
// SPI2X=1; //Double speed for SPI = 8MHz @16MHz Clock
 SPSR=0x01;

 return 0;
}


#endif //MMC_CARD_SPI