Servo - September 2011

 byte = cmd | 0x40;
  SD_Write(byte);
 // send command packet (6 bytes)
byte = addr>>24;
  SD_Write(byte);
 // msb of the address
  byte = addr>>16;
  SD_Write(byte);
  byte = addr>>8;
  SD_Write(byte);
  SD_Write( addr);
 // lsb
SD_Write(CRC7);
 // Not used unless CRC mode on
// now wait for a response (allow for up
// to 8 bytes delay)
n = 9;
do {
  res = SD_Read();
 // check if ready
  if ( res != 0xFF)
 break;
} while ( —n > 0);

return (res);
 // return the result
}
void SD_InitSPI( void)
/**
* Configure the SD card SPI bus hardware
* settings and software. *
*** Using the SD SPI mode spec settings
* instead of the MCHP example.
*
*
*
*
*
*
*/
{
  nMEM_CS = 1;
 // De-select the SD card
PRECONDITION: none
INPUTS: none - The hardware is explicitly
set up
OUTPUTS: none
RETURNS: none.

if (sdcard.cardInit == 1) {
 return;

}
  // init spi module for a slow (init) clock
  // speed, 8 bit byte mode
  // Master, CKE=0; CKP=1, sample end,
  // prescale 1:64 (250KHz)
SPI1STATbits.SPIEN = 0;
 // disable SPI for configuration
  SPI1CON1 = 0x027c;
  SPI1CON2 = 0x0000;
 // No buffer, no frame mode
  SPI1STAT = 0x8000;
 // enable
}
uint8_t SD_InitMedia( void)
/**
*  Discover the type and version of the
*  installed SD card.  This routine will find
*  any SD or SDHC card and properly set it up.
*
*  PRECONDITION: none
*  INPUTS: none
*  OUTPUTS: none
*  RETURNS: 0 if successful, some other
*  error if not.
*/
{
  uint16_t n;
  uint8_t res = 0;
  // // If we get that far...

uint32_t timer;
uint8_t cmd;
uint8_t db[16];
  // when we get data back to look at
if (sdcard.cardInit == 1) {
 return(0);
  // done, don’t do it again.
}
// 1. start with the card not selected
SD_Disable();
// 2. send 80 clock cycles so card can
// init registers
for ( n=0; n<10; n++)
 SD_Clock();
// 3. now select the card
SD_Enable();

// 4. send a reset command and look for
// “IDLE”
res = SD_SendCmd( RESET, 0); SD_Disable();
if ( res != 1) {
 SD_Disable();
 return(LOG_FAIL);
 // card did not respond with “idle”
}
// 5. Check card voltage (type) for SD 1.0
// or SD 2.0
res = SD_SendCmd(SEND_IF_COND, 0x000001AA);
// didn’t respond or responded with an
// “illegal cmd”
if ( (res == 0xFF) || (res == 0x05)) {
 sdcard.cardVer = 1;
 // means it’s an SD 1.0 or MMC card
 // 6. send INIT until receive a 0 or
// 300ms passes
 timer = t_1ms + 300;
  while(timer > t_1ms) {
 res = SD_SendCmd(INIT,0);
 SD_Disable();
 // SendSDCmd() enables SD card
 if (!res) {
 break;
 // The card is ready
 }
}
if (res != 0) {
 return(LOG_FAIL);
 // failed to reset.

}
SD_Disable();
 // remember to disable the card
 }
else {  // need to pick up 4 bytes for v2
 card voltage description
 sdcard.cardVer = 2;
 // SD version 2.0 card
 for (n=0; n<4; n++) {
 db[n] = SD_Read();

}
// but we’ll ignore these bytes
SD_Disable();

// 6. send INIT or SEND_APP_OP
// repeatedly until receive a 0
cmd = SEND_APP_OP;
timer = t_1ms + 300;
// wait up to .3 seconds for life
// will still be in idle mode (0x01)
// after this
res = SD_SendCmd(APP_CMD, 0);
SD_Disable();
while (timer > t_1ms) {
 res = SD_SendCmd(cmd, 0x40000000);
SD_Disable();