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int mmc_init();
int mmc_response(unsigned char response);
int mmc_read_block(unsigned long block_number);
int mmc_write_block(unsigned long block_number);
int mmc_get_status();


/************************** MMC Init **************************************/
/* Initialises the MMC into SPI mode and sets block size, returns 0 on success */

int mmc_init()
{
int i;

SETUP_SPI(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_4 | SPI_SS_DISABLED);

*0x94 |= 0x40; // set CKE = 1 - clock idle low
*0x14 &= 0xEF; // set CKP = 0 - data valid on rising edge

OUTPUT_HIGH(PIN_C2); // set SS = 1 (off)

for(i=0;i<10;i++) // initialise the MMC card into SPI mode by sending clks on
{
SPI_WRITE(0xFF);
}

OUTPUT_LOW(PIN_C2); // set SS = 0 (on) tells card to go to spi mode when it receives reset

SPI_WRITE(0x40); // send reset command
SPI_WRITE(0x00); // all the arguments are 0x00 for the reset command
SPI_WRITE(0x00);
SPI_WRITE(0x00);
SPI_WRITE(0x00);
SPI_WRITE(0x95); // precalculated checksum as we are still in MMC mode

puts("Sent go to SPI\n\r");

if(mmc_response(0x01)==1) return 1; // if = 1 then there was a timeout waiting for 0x01 from the mmc

puts("Got response from MMC\n\r");

i = 0;

while((i < 255) && (mmc_response(0x00)==1)) // must keep sending command if response
{
SPI_WRITE(0x41); // send mmc command one to bring out of idle state
SPI_WRITE(0x00); // all the arguments are 0x00 for command one
SPI_WRITE(0x00);
SPI_WRITE(0x00);
SPI_WRITE(0x00);
SPI_WRITE(0xFF); // checksum is no longer required but we always send 0xFF
i++;
}
if(i >= 254) return 1; // if >= 254 then there was a timeout waiting for 0x00 from the mmc

puts("Got out of idle response from MMC\n\r");

OUTPUT_HIGH(PIN_C2); // set SS = 1 (off)

SPI_WRITE(0xFF); // extra clocks to allow mmc to finish off what it is doing

OUTPUT_LOW(PIN_C2); // set SS = 0 (on)

SPI_WRITE(0x50); // send mmc command one to bring out of idle state
SPI_WRITE(0x00);
SPI_WRITE(0x00);
SPI_WRITE(0x02); // high block length bits - 512 bytes
SPI_WRITE(0x00); // low block length bits
SPI_WRITE(0xFF); // checksum is no longer required but we always send 0xFF

if((mmc_response(0x00))==1) return 1;
OUTPUT_HIGH(PIN_C2); // set SS = 1 (off)
puts("Got set block length response from MMC\n\r");
return 0;
}

/************************** MMC Get Status **************************************/
/* Get the status register of the MMC, for debugging purposes */

int mmc_get_status()
{

OUTPUT_LOW(PIN_C2); // set SS = 0 (on)

SPI_WRITE(0x58); // send mmc command one to bring out of idle state
SPI_WRITE(0x00);
SPI_WRITE(0x00);
SPI_WRITE(0x00); //
SPI_WRITE(0x00); // always zero as mulitples of 512
SPI_WRITE(0xFF); // checksum is no longer required but we always send 0xFF

OUTPUT_HIGH(PIN_C2); // set SS = 1 (off)
return 0;
}

/************************** MMC Write Block **************************************/

int mmc_write_block(unsigned long block_number)
{
unsigned long i;
unsigned long varh,varl;

varl=((block_number&0x003F)<<9);
varh=((block_number&0xFFC0)>>7);

puts("Write block\n\r"); // block size has been set in mmc_init()

OUTPUT_LOW(PIN_C2); // set SS = 0 (on)

SPI_WRITE(0x58); // send mmc write block
SPI_WRITE(HIGH(varh));
SPI_WRITE(LOW(varh));
SPI_WRITE(HIGH(varl));
SPI_WRITE(0x00); // always zero as mulitples of 512
SPI_WRITE(0xFF); // checksum is no longer required but we always send 0xFF

if((mmc_response(0x00))==1) return 1;
puts("Got response to write block\n\r");

SPI_WRITE(0xFE); // send data token

for(i=0;i<512;i++)
{

SPI_WRITE(i2c_eeprom_read(HIGH(i),LOW(i))); // send data

}

SPI_WRITE(0xFF); // dummy CRC
SPI_WRITE(0xFF);

if((SPI_READ(0xFF)&0x0F)!=0x05) return 1;

puts("Got data response to write block\n\r");

OUTPUT_HIGH(PIN_C2); // set SS = 1 (off)
return 0;
}

/************************** MMC Read Block **************************************/
/**** Reads a 512 Byte block from the MMC and outputs each byte to RS232 ****/

int mmc_read_block(unsigned long block_number)
{
unsigned long i;
unsigned long varh,varl;

varl=((block_number&0x003F)<<9);
varh=((block_number&0xFFC0)>>7);

OUTPUT_LOW(PIN_C2); // set SS = 0 (on)

SPI_WRITE(0x51); // send mmc read single block command
SPI_WRITE(HIGH(varh)); // arguments are address
SPI_WRITE(LOW(varh));
SPI_WRITE(HIGH(varl));
SPI_WRITE(0x00);
SPI_WRITE(0xFF); // checksum is no longer required but we always send 0xFF

if((mmc_response(0x00))==1) return 1; // if mmc_response returns 1 then we failed to get a 0x00 response (affirmative)

puts("Got response to read block command\n\r");

if((mmc_response(0xFE))==1) return 1; // wait for data token

puts("Got data token\n\r");

for(i=0;i<512;i++)
{
putc(SPI_READ(0xFF)); // we should now receive 512 bytes
}

SPI_READ(0xFF); // CRC bytes that are not needed
SPI_READ(0xFF);

OUTPUT_HIGH(PIN_C2); // set SS = 1 (off)
SPI_WRITE(0xFF); // give mmc the clocks it needs to finish off

puts("\n\rEnd of read block\n\r");

return 0;
}

/************************** MMC get response **************************************/
/**** Repeatedly reads the MMC until we get the response we want or timeout ****/

int mmc_response(unsigned char response)
{
unsigned long count = 0xFFFF; // 16bit repeat, it may be possible to shrink this to 8 bit but there is not much point

while(SPI_READ(0xFF) != response && --count > 0);

if(count==0) return 1; // loop was exited due to timeout
else return 0; // loop was exited before timeout
}
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