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Problem with MMC initialization

 
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ROBOTICAR



Joined: 28 Aug 2007
Posts: 45

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Problem with MMC initialization
PostPosted: Wed Nov 12, 2008 7:46 am     Reply with quote
I want to write MMC library . But I have a problem at the beginning . In this code the first level or reset MMC (GO_IDLE_STATE) is successful and MMC return 0x01.but in next level or SEND_OP_COND MMC return 0xFF instead 0x00. Where is the problem? My Compiler is 4.057 and proteus 6.9 here is the like of code and proteus file .

http://rapidshare.com/files/163053853/MMC_TEST.rar.html

Code:

#include "mmc1.h"

////////////////////////////////////////////////////////////////////////////////
#define GO_IDLE_STATE 0
#define SEND_OP_COND 1
#define CS PIN_C2
////////////////////////////////////////////////////////////////////////////////
char Command(unsigned int cmd, unsigned int arg)
{ 

     // sends a command to the MMC
        unsigned char resp;
        unsigned char retry=0;
        output_high(CS);
        output_low(CS);
        spi_write(0xFF);
        spi_write(cmd | 0x40);                               
        spi_write(arg>>24);
        spi_write(arg>>16);
        spi_write(arg>>8);
        spi_write(arg);
        spi_write(0x95);   
        spi_write(0xFF);
        while((resp = spi_read(0xFF)) == 0xFF)
                if(retry++ > 8) break;   
        return resp;
}

void main()
{
   int i;
   char R1;
   setup_spi(SPI_MASTER | SPI_L_TO_H | SPI_CLK_DIV_16);
   /////////////////////////////////////////////////////////////////////////////
   output_high(CS);                     //   _   
   for(i=0;i<10;i++)                    //    |
      Spi_Write(0xFF);                  //    |     ...: CMD0 :...
   R1=Command(GO_IDLE_STATE,0);         //    |
   printf("CMD0=%x\r\n",R1);            //   _|
   /////////////////////////////////////////////////////////////////////////////
   R1=Command(SEND_OP_COND,0);          //    |     ...: CMD1 :...
   printf("CMD1=%x\r\n",R1);            //    |
   /////////////////////////////////////////////////////////////////////////////

}
ckielstra



Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands

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PostPosted: Wed Nov 12, 2008 6:37 pm     Reply with quote
Why not use the CCS provided MMC driver mmcsd.c?

Code:
        spi_write(arg>>24);
Your function definition defines arg as an 8-bit integer, the shift of 24 bits will fail...
Define as an int32 instead.

Code:
   setup_spi(SPI_MASTER | SPI_L_TO_H | SPI_CLK_DIV_16);
MMC cards work either in SPI mode 0 or 3. Here you have defined SPI mode 1. Try the following code instead:
Code:
#define SPI_MODE_0  (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1  (SPI_L_TO_H)
#define SPI_MODE_2  (SPI_H_TO_L)
#define SPI_MODE_3  (SPI_H_TO_L | SPI_XMIT_L_TO_H)

setup_spi(SPI_MASTER | SPI_MODE_0 | SPI_CLK_DIV_16);


Code:
        while((resp = spi_read(0xFF)) == 0xFF)
                if(retry++ > 8) break;   
The 8 retries probably are too short for some commands.
Another thing I don't like here is that you have an assignment ('=') inside the while test. This makes your code difficult to read and is difficult to step through with a debugger. Another way to write the same code is:
Code:
while(retry++ < 255)
{
  resp = spi_read(0xFF);
  if (resp != 0xFF)
    break;
}
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