// 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/#mmcint 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 edgeOUTPUT_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 resetSPI_WRITE(0x40);                        // send reset commandSPI_WRITE(0x00);                        // all the arguments are 0x00 for the reset commandSPI_WRITE(0x00);SPI_WRITE(0x00);SPI_WRITE(0x00);SPI_WRITE(0x95);                        // precalculated checksum as we are still in MMC modeputs("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 mmcputs("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 mmcputs("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 doingOUTPUT_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 0xFFif((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 0xFFOUTPUT_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 0xFFif((mmc_response(0x00))==1) return 1;puts("Got response to write block\n\r");SPI_WRITE(0xFE);                        // send data tokenfor(i=0;i<512;i++){SPI_WRITE(i2c_eeprom_read(HIGH(i),LOW(i)));     // send data}SPI_WRITE(0xFF);                        // dummy CRCSPI_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 0xFFif((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 tokenputs("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 neededSPI_READ(0xFF);OUTPUT_HIGH(PIN_C2);            // set SS = 1 (off)SPI_WRITE(0xFF);                // give mmc the clocks it needs to finish offputs("\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}