int readSECTOR( LBA a, char *p)
// a LBA (logic block address) of sector requested
// p ponter to sector buffer
// returns TRUE if succesful
{
int r, i;
// 1. send READ command
sendSDCmd(READ_SINGLE, (a <<9));
if ( r == 0) //check if command was received
{
// 2. wait for a response
for( i=0; i<R_TIMEOUT; i++)
{
r = readSPI();
if ( r == DATA_START)
break;
}
// 3. if it did not timeout, read 512 byte of data
if ( i != R_TIMEOUT)
{
i = 512
do {
*p++ = readSPI();
} while (---i>0);
// 4. ignore CRC
readSPI();
readSPI();
} // data arrived
} // command accepted
// a LBA of sector requested
// p pointer to sector buffer
// returns TRUE if successful
int writeSECTOR(LBA a, char *p)
{
unsigned r, i;
// 0. check Write Protect
if (getWP())
return FAIL;
// 1. send WRITE command
r = sendSDCmd(WRITE_SINGLE, (a << 9));
if (r == 0) // check if command was accepted
{
// 2. send data
writeSPI(DATA_START);
// send 512 bytes of data
for(i=0; i<512; i++)
writeSPI(*p++);
// 3. send dummy CRC
clockSPI();
clockSPI();
// 4. check if data accepted
r = readSPI();
if ((r & 0xf) == DATA_ACCEPT)
{
#ifdef WRITE_LED
digitalwrite(WRITE_LED, 0);
#endif
// 5. wait for write completion
for(i=0; i<W_TIMEOUT; i++)
{
r = readSPI();
if (r != 0 )
break;
}
#ifdef WRITE_LED
digitalwrite(WRITE_LED, 1);
#endif
} // accepted
else
{
r = FAIL;
}
} // command accepted
// 6. disable the card
disableSD();
return (r); // return TRUE if successful
} // writeSECTOR
int initMedia( void)
//returns 0 if succesful
// E_COMMAND_ACK failed to acknowledge reset command
// E_INIT_TIMEOUT failed to initialize
{
int i, r;
;
// 1. with the card NOT selected
disableSD();
// 2. send 80 clock cycles start up
for(i=0;i<80;i++)
clockSPI();
// 3. now select the card
enableSD();
// 4. send a single RESET commmand
r = sendSDCmd( RESET, 0);
disableSD();
if ( r != 1) // must return Idle
return E_COMMAND_ACK;
// 5. send repeatedly INIT until Idle terminates
for (i=0; i<I_TIMEOUT; i++)
{
r = sendSDCmd( INIT, 0); disableSD();
if ( !r)
break;
}
if ( i == I_TIMEOUT)
return E_INIT_TIMEOUT; // init timed out
// 6. increase speed
SPI3ACON = 0; // disable the SPI2 module
SPI3ABRG = 0; // Fpb/(2*(0+1)) = 20/2 = 10MHz
SPI3ACON = 0x8120; // re-enable the SPI2 module
return 0;
} //init media
// a LBA of sector requested
// p pointer to sector buffer
// returns TRUE if successful
int readSECTOR(LBA a, char *p)
{
int r, i;
#ifdef READ_LED
digitalwrite(READ_LED, 0);
#endif
// 1. send READ command
r = sendSDCmd(READ_SINGLE, (a << 9));
if (r == 0) // check if command was accepted
{
// 2. wait for a response
for(i=0; i<R_TIMEOUT; i++)
{
r = readSPI();
if (r == DATA_START)
break;
}
// 3. if it did not timeout, read 512 byte of data
if (i != R_TIMEOUT)
{
i = 512;
do{
*p++ = readSPI();
} while (--i>0);
// 4. ignore CRC
readSPI();
readSPI();
} // data arrived
} // command accepted
// 5. remember to disable the card
disableSD();
#ifdef READLED
digital(READ_LED, 1);
#endif
return (r == DATA_START); // return TRUE if successful
} // readSECTOR
