// Written by Ed Waugh 2004, www.edwaugh.co.uk
// for the original source, and hundreds more examples of PIC C code, see:
// http://www.microchipc.com/sourcecode/#mmc
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
}
