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SD Card example design using standalone?

Former Member

Hello folks,

Quick question:  Is it possible to do read/writes to an SD card using standalone (bare-metal) OS? 

I tried building a Zynq-based SDK project with a standalone BSP + xilfatfs.  However when I do so I get this error in SDK:

ERROR:EDK:3900 - issued from TCL procedure "::sw_xilfatfs_v1_00_a::xilfatfs_drc"
   line 15
   xilfatfs () - Sysace HW module not present or not accessible from this
   processor. FATfs cannot be used without this module

So my guess is, standalone OS doesn't have libraries for SD/MMC support...

I know the typical flow is to use U-boot/Linux, but my application will be *dumb* simple and U-boot/Linux would be unnecessary overhead. 

The application will simply move a file from SD card over to memory, and buffer the data via GPIOs to an external device.

Thanks,

Eddie

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    I'm currently working on SDCard access for my real-time operating system, which is based on FreeRTOS. Unfortunately there seems to be little to no support from Xilinx for doing this.

    The other problem is that there really isn't much useful information for handling SD cards using the SDIO protocol. (SPI mode there is a lot of documentation from hobbyists etc, as seen from the provided link).

    There are the SDHCI simplified specs, which are useful, but don't seem to provide all the information you need.

    Anyway, fortunately there are a few reference drivers you can look at for help.

    Obviously there's linux, which provides the most fully featured driver possible, and its pretty complex. As mentioned earlier I'd avoid this unless you have to.

    Also the raspberrypi is using an SDHCI controller, similar to that in Zynq.

    See:
    https://github.com/jameswalmsley/rpi-boot/blob/master/emmc.c

    They seem to have full read access to the card, and from that write access should be trivial.

    In anycase, I shall have my fully featured driver ready in 2/3 weeks from now (hopefully). So checkout:
    https://github.com/jameswalmsley/bitthunder/

    The source will be found under: drivers/mmc/host/sdhci.c

    Hope this helps someone.

    James

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  • 0

    I'm currently working on SDCard access for my real-time operating system, which is based on FreeRTOS. Unfortunately there seems to be little to no support from Xilinx for doing this.

    The other problem is that there really isn't much useful information for handling SD cards using the SDIO protocol. (SPI mode there is a lot of documentation from hobbyists etc, as seen from the provided link).

    There are the SDHCI simplified specs, which are useful, but don't seem to provide all the information you need.

    Anyway, fortunately there are a few reference drivers you can look at for help.

    Obviously there's linux, which provides the most fully featured driver possible, and its pretty complex. As mentioned earlier I'd avoid this unless you have to.

    Also the raspberrypi is using an SDHCI controller, similar to that in Zynq.

    See:
    https://github.com/jameswalmsley/rpi-boot/blob/master/emmc.c

    They seem to have full read access to the card, and from that write access should be trivial.

    In anycase, I shall have my fully featured driver ready in 2/3 weeks from now (hopefully). So checkout:
    https://github.com/jameswalmsley/bitthunder/

    The source will be found under: drivers/mmc/host/sdhci.c

    Hope this helps someone.

    James

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