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Error reading from different sd card

 
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Audi80



Joined: 07 Sep 2007
Posts: 41

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Error reading from different sd card
PostPosted: Tue Jan 27, 2009 11:19 am     Reply with quote
Hi there, i´ve got a working MP3 player project with a 18F4620 that took a long to get it working, but now that its done i´ve several clones Very Happy and brought new sd cards, my problem is that i think that the new cards are faster than the old card i´ve used for debug. The old card is a kingston 1Gb the new card as Silicon Power 1Gb too, what could possibly be wrong?

My answer is if i can make the mmc_init routine to work with the new cards why dont i get response when i try to read from it??

here´s my initialization routine

Code:

int mmc_init(){
char p;
int i;
   SETUP_SPI(SPI_MASTER | SPI_L_TO_H | SPI_CLK_DIV_4 | SPI_SS_DISABLED);
   SSPSTAT |= 0x40;                       
   SSPCON &= 0xEF;                       
   SS=1;
   for(i=0;i<10;i++){
           SPI_WRITE(0xFF);
   }
   SS=0;
   SPI_WRITE(0x40);
   for(p=4;p>0;p--){
      SPI_WRITE(0x00);
   }
   SPI_WRITE(0x95); 

   if(mmc_response(0x01)==1) return 1;     

   i = 0;
   while((i < 255) && (mmc_response(0x00)==1)){
           SPI_WRITE(0x41);
      for(p=4;p>0;p--){
              SPI_WRITE(0x00);
      }
           SPI_WRITE(0xFF);     
           i++;
   }
   if(i >= 254) return 1;                 
   SS=1;
   SPI_WRITE(0xFF);
   SS=0;
   SPI_WRITE(0x50); 
   SPI_WRITE(0x00);
   SPI_WRITE(0x00);
   SPI_WRITE(0x02);
   SPI_WRITE(0x00);
   SPI_WRITE(0xFF);
   if((mmc_response(0x00))==1) return 1;
   SS=1;
   return 0;
}


I´ve get it in the net while googling...

Any help would be appreciated. Very Happy
asmallri



Joined: 12 Aug 2004
Posts: 1634
Location: Perth, Australia

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PostPosted: Tue Jan 27, 2009 1:55 pm     Reply with quote
Just because the Kingston card is older does not mean its slower. One of the slowest cards I have tested is a brand new SANdisk 8GB card.

I see a couple of problems.

The initial flushing of the SPI bus is meant to be done BEFORE you select the SD card.

You are not waiting long enough for the card to become ready. it can take 500ms. Inside your "i" for loop insert a 2ms delay.
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http://www.brushelectronics.com/software
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