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Problem using SD card

Former Member

Hi there,

I need some advice.  I am trying to use a SD card on a MicroZed board.  The board is loaded with a bare bones Zynq processor system all configured as per the board support package defaults.  I have booted linux on this board from that card before so know it is electrically all OK.  I am now just working on a basic SD card read and write using the Xilinx driver, no file system at this stage.  The code I am using is:

XSdPs_Config * sd0Cfg = XSdPs_LookupConfig(XPAR_PS7_SD_0_DEVICE_ID);//XPAR_PS7_SD_0_BASEADDR

int err = XSdPs_CfgInitialize(&sd0Inst, sd0Cfg, sd0Cfg->BaseAddress);

if(err == XST_SUCCESS)

{

err = XSdPs_SdCardInitialize(&sd0Inst);

if(err == XST_SUCCESS)

{

err = XSdPs_ReadPolled(&sd0Inst, 1, 1, buf);



}

}


The problem I have is that  XSdPs_SdCardInitialize fails UNLESS I step through it where it passes.  The problem happens somewhere in this code of  XSdPs_SdCardInitialize:

/*

* Send ACMD41 while card is still busy with power up

*/

while ((RespOCR & XSDPS_RESPOCR_READY) == 0) {

Status = XSdPs_CmdTransfer(InstancePtr, CMD55, 0, 0);

if (Status != XST_SUCCESS) {

Status = XST_FAILURE;

goto RETURN_PATH;

}



/*

* 0x40300000 - Host High Capacity support & 3.3V window

*/

Status = XSdPs_CmdTransfer(InstancePtr, ACMD41,

(XSDPS_ACMD41_HCS | XSDPS_ACMD41_3V3), 0);

if (Status != XST_SUCCESS) {

Status = XST_FAILURE;

goto RETURN_PATH;

}



/*

* Response with card capacity

*/

RespOCR = XSdPs_ReadReg(InstancePtr->Config.BaseAddress,

XSDPS_RESP0_OFFSET);



}

If I allow the processor to run to the first line of this code, then single step through it, then run again it succeeds!  It seems the only way it can fail is if one of the calls to XSdPs_CmdTransfer fails.  Not sure why they fail at full speed but OK on single stepping.

I have also tried changing the clock frequency to 25MHz and changing the pins slew rate to fast.  With the clock frequency the SD Init function seems to pass most times but the SD read function still fails every time.

Any advice would be greatly appreciated.  I will add any other information required if you ask.


Thanks

  • 0

    Hi ashesman,

    Any reason why you need SD card access without using an operating system?

    It seems that others have come across similar challenges in getting this to work under baremetal execution.  Have you already reviewed these other forum threads?

    http://microzed.org/content/standalone-sd-card-sdio

    http://microzed.org/content/sd-card-example-design-using-standalone

    Regards,

    -Kevin

  • 0 in reply to zedhed

    Hi Kevin,

    Yes, I have read the threads.  There is one note in there about changing the SDIO and GPIO pins around which I did not quite understand.

    I am using an operating system, but not one that just works with this SDIO controller.  I am using FreeRTOS and its supported fat file system.  I will replace the ram disk implementation with SD card.  But, for now I can not even read a block from the card.  Once I can read and write to the card then I will use the OS.

    A little frustrating that the standard BSP and Vivado block automation do not just work to configure the SDIO and driver to just work.  I am sure it can be fixed...

    Cheers

    Ashley

  • 0

    Update:  I tried using the Xilinx fat fs and it works perfectly.  It uses the SDIo driver functions so I can follow my way through the low level driver layer and find the answer in there.  It calls a few more functions during init than I did so will see what I can do...

  • 0

    For future reference, the file diskio.c in the xilinx fat file system has the answer in it.  You can use the following code to bare metal init and read from a SD card but it would make mmore sense to just use diskio.c and diskio.h to init and read etc.





    XSdPs sd0Inst;

    u8 buf[520];



    #define HIGH_SPEED_SUPPORT 0x01

    #define WIDTH_4_BIT_SUPPORT 0x4



    int SD0Init(void)

    {

    u8 SCR[8] __attribute__ ((aligned(32)));

    u8 ReadBuff[64] __attribute__ ((aligned(32)));



    XSdPs_Config *SdConfig;



    /*

    * Check if card is in the socket

    */

    u32 StatusReg = XSdPs_GetPresentStatusReg(XPAR_XSDPS_0_BASEADDR);

    if ((StatusReg & XSDPS_PSR_CARD_INSRT_MASK) == 0)

    {

    // No disk

    return 1;

    }

    else

    {

    if (StatusReg & XSDPS_PSR_WPS_PL_MASK)

    {

    // Not write protected

    }

    else

    {

    // Write protected

    }

    }



    u3000

    /*

    * Initialize the host controller

    */

    SdConfig = XSdPs_LookupConfig(XPAR_PS7_SD_0_DEVICE_ID);

    if (NULL == SdConfig)

    {

    return 1;

    }



    int Status = XSdPs_CfgInitialize(&sd0Inst, SdConfig, SdConfig->BaseAddress);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    Status = XSdPs_SdCardInitialize(&sd0Inst);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    Status = XSdPs_Change_ClkFreq(&sd0Inst, 25000000/*XPAR_PS7_SD_0_SDIO_CLK_FREQ_HZ*/);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    Status = XSdPs_Select_Card(&sd0Inst);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    Status = XSdPs_Get_BusWidth(&sd0Inst, SCR);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    Status = XSdPs_Get_BusSpeed(&sd0Inst, ReadBuff);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    if(ReadBuff[13] & HIGH_SPEED_SUPPORT)

    {

    Status = XSdPs_Change_BusSpeed(&sd0Inst);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }

    }



    Status = XSdPs_Pullup(&sd0Inst);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    if (SCR[1] & WIDTH_4_BIT_SUPPORT)

    {

    Status = XSdPs_Change_BusWidth(&sd0Inst);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }

    }



    Status = XSdPs_SetBlkSize(&sd0Inst, XSDPS_BLK_SIZE_512_MASK);

    if (Status != XST_SUCCESS)

    {

    return 1;

    }



    }



    void main_blinky( void )

    {

    print("Readyr
    ");



    int err = SD0Init();

    if(err == XST_SUCCESS)

    {

    print("SD Init Passedr
    ");

    err = XSdPs_ReadPolled(&sd0Inst, 1, 1, buf);

    if(err == XST_SUCCESS)

    {

    print("SD Card Read Passedr
    ");

    }

    else

    {

    print("SD Card Read Failedr
    ");

    }

    }

    else

    {

    print("SD Init Failed!");

    }


  • 0

    Hi Ashley,

    Thanks for responding back with what worked for you so that the community can benefit from this knowledge.

    Regards,

    -Kevin