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AM3352: SD CARD: CARD DETECT PIN

Krishan Arora
Prodigy 40 points

Part Number: AM3352

Hello,

I am currently working on the SD card interface design using the MMC0 peripheral on the AM3352 processor.
According to the datasheet, a dedicated MMC0_SDCD pin is available for card detection. However, due to routing constraints and pin multiplexing optimization, I would like to confirm if we can route the SD card's physical Card Detect (CD) pin to any standard AM3352 GPIO instead of the dedicated MMC0_SDCD pin.
Please review and confirm if using an alternate GPIO for the card detect line is acceptable  or if there are specific hardware constraints requiring the native MMC0_SDCD pin.
 
Warm Regards,
Krishan Arora
  • 0
    TI__Guru**** 232585 points

    Krishan Arora,

    Thank you for the query.

    I am checking internally.

    Do you have the SD card interface with MMC0_SDCD pin configured for card detection.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 40 points

    Hi Sreenivasa,

    No, the MMC0_SDCD pin is NOT configured for SD card detection in our design.

    Due to strict pin multiplexing constraints, we are forced to repurpose the physical MMC0_SDCD pin to handle a completely different, critical system interrupt. Because of this, we intend to route the physical SD card socket's Card Detect (CD) signal to a standard, general-purpose GPIO on a different bank.

    Crucially, MMC0 (the SD card interface) is configured as one of the primary BOOT options in our design.

    Could you please review and confirm the following two points:

    1. ROM Bootloader Implications: Does the AM335x ROM code rely on the physical state of the native MMC0_SDCD pin to initiate the boot process from MMC0? If we bypass this native pin, will the RBL still attempt to initialize and boot from the SD card, or will it assume no card is present and skip to the next boot device?

    2. OS/Driver Implications: Assuming the board can successfully boot, are there any underlying hardware constraints in the MMC0 peripheral if we completely decouple it from the native CD pin? Can you confirm the standard AM335x MMC driver will seamlessly support card detection via a generic GPIO without hardware state machine errors?

  • 0 in reply to Krishan Arora
    TI__Guru**** 232585 points

    Hello Krishan Arora,

    Thank you for the inputs.

    Let me check with the team internally.

    The software expert is out of office this week and there could be delay in replying.

    Regards,

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Guru**** 232585 points

    Hello Krishan Arora,

    Please refer below inputs from the expert:

    The card detect can use the native CD pinmux or GPIO mode. Linux MMC driver supports both.

    (+) AM3358: SD Card detect pin- Hardware/software change requirements - Processors forum - Processors - TI E2E support forums

    Regards,

    Sreenivasa