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ZedBoard SD card extender

ejubenville

I am trying to use an off-the-shelf cable that extends the SD card on a ZedBoard, but it doesn't work.  The extender cable is 15" long, and works on other devices to extend their SD cards slots, but when used on the ZedBoard the board refuses to boot.  Nothing is displayed on the console, and the blue LED indicating a completed FPGA load doesn't come on.

Does anyone know any reason why the ZedBoard SD card couldn't be extended, or anything special I would have to do to make it work?

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    Did some debugging on the signals on the SD card extender.  Poor signal quality was observed at extended end socket on IO CMD pin 2 although CLK pin 5 had good edge integrity.  The passive 8pF probe probably changed/degraded measurement a little, but nonetheless CMD line had significant edge ringing.

    Reduced the length of flex ribbon assembly (with alternating grounds) to about 7u201D and the signal integrity improved.  ZedBoard was able to read the SD card properly.

    Knowing that the extender worked on a laptop PC without a problem, the unique characteristics of the ZedBoard SD card slot must certainly be a factor. 

    The fix is not fully validated over time or with anything but class 4 SD card.

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    Did some debugging on the signals on the SD card extender.  Poor signal quality was observed at extended end socket on IO CMD pin 2 although CLK pin 5 had good edge integrity.  The passive 8pF probe probably changed/degraded measurement a little, but nonetheless CMD line had significant edge ringing.

    Reduced the length of flex ribbon assembly (with alternating grounds) to about 7u201D and the signal integrity improved.  ZedBoard was able to read the SD card properly.

    Knowing that the extender worked on a laptop PC without a problem, the unique characteristics of the ZedBoard SD card slot must certainly be a factor. 

    The fix is not fully validated over time or with anything but class 4 SD card.

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