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SK-AM64: SD boot failure

Daisuke Maeda
Guru 20205 points

Part Number: SK-AM64

Our customer failed to boot with an SD card (low speed class) created with the pre-built image of Linux SDK 7.3.

software-dl.ti.com/.../tisdk-default-image-am64xx-evm.wic.xz

They succeeded to boot with a V10 certified SD card, referring to the post below.

e2e.ti.com/.../3717264
"The forth SD card (with latest technologies enabled, V10 certified) actually made this system to work."

What are the supported speed classes for SD card boot?

If the speed class of supported SD cards is limited, what is the cause of this limitation? Is it the device (AM65x), the board (SK-AM64) or the software (Linux kernel or U-Boot)?

Best regards,

Daisuke

  • 0
    TI__Guru** 101650 points

    Hello Daisuke,

    Before we go into speed classes, did you make sure that the SD card is 16GB or larger as per the Quick Start Guide?
    https://dev.ti.com/tirex/content/tirex-product-tree/am64x-devtools/docs/am64x_skevm_quick_start_guide.html

    I have had issues with using an 8GB card.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    Guru 20205 points

    Hi Nick-san,

    Thank you for your reply.

    Our customer had the issue using their 32GB card. They will check the details of the card.

    Best regards,

    Daisuke

  • 0 in reply to Daisuke Maeda
    TI__Guru** 101650 points

    Hello Daisuke,

    I am sending this to our hardware owner to comment on whether there are any SD card limitations from the device / board side.

    Regards,

    Nick

  • 0 in reply to Nick Saulnier
    TI__Guru 63125 points

    I'm not aware of any SOC hardware limitation that would prevent the system from booting when using a legacy (non-UHS-I) SD Card.

    I reviewed the AM64x SK EVM SD Card connectivity to the AM64x device and noticed pull-ups associated with the SD Card signals are marked DNI. I recommend installing these resistors since the AM64x pins are off by default which means the SD Card inputs could float to invalid logic levels until software initializes IOs associated with the SD Card signals.  I also recommend an external pull-down on MMC1_CLK to hold it low until software initializes IOs associated with the SD Card signals. I was not able to find a location to install the pull-down on MMC1_CLK so this may require a PCB modification.

    I will assign this thread to the EVM team for further comments.

    Regards,
    Paul 

  • 0 in reply to peaves
    TI__Genius 15920 points

    Hi Daisuke,

    Paul was referencing an old schematic.  The pull-ups associated with the SD Cards signals are populated on the AM64x SK EVM.  However, there is not a external pull-down on MMC1_CLK. 

    Can you add this pull-down on your board without creating any signal integrity issues and share if this resolves your issue?

    Regards,

    Melissa

  • 0 in reply to melissaw
    Guru 20205 points

    Hi Melissa-san, Paul-san and Nick-san,

    Thank you for your reply.

    SK-AM64 does not have a pad for the pull-down on MMC1_CLK, so the pull-down cannot be added.

    By the way, our customer has both SK-AM64 and TMDS64GPEVM, and the SD card that failed with SK-AM64 worked fine when used with TMDS64GPEVM.

    Best regards,

    Daisuke

  • 0 in reply to melissaw
    Guru 20205 points

    Melissa-san,

    > SK-AM64 does not have a pad for the pull-down on MMC1_CLK, so the pull-down cannot be added.

    Should our customer try to use a 10kΩ lead linear resistor for the pull-down on MMC1_CLK?

    Best regards,

    Daisuke