9 Replies Latest reply on Mar 17, 2020 9:15 AM by javierns

    SD card not detected (Zedboard + FMCommS4)

    javierns

      Hi everyone,

      I am having some troubles trying to boot the Linux distribution for the FMCommS4 on a Zedboard from an SD card connected to the board via extension cable. It does not detect the SD card and therefore it does not boot.

      If I connect the SD card directly to the board it works OK, but if I use the cable extension it seems the board is not able to detect the SD card. I have made some measures with the oscilloscope trying to find out the origin the problem and I have came up with the following ideas:

      * When the SD card is directly connected to the board:

      - The clk pin of the SD interface start at a frequency of 200 kHz and the changes to 25 MHz.

      - The SD receive some cmd when clk is at 200 kHz

      - Data pins start to wiggle when clk freq. is 25 MHz

      * When there is NO SD card connected

      - The clk pin of the SD interface start at a frequency of 200 kHz for a while and after some time it stay fixed at a high level.

      - The SD receive some cmd

      - Data pins does not wiggle.

      * When the SD is connected to the board trough the extensión cable: same behaviour as when there is NO SD card.

       

      I have checked CD (Card Detected) and WP (Write Protection) pins and everything seems to work fine.

      On the hand, I wondered if this problem this problem was related to noise or EMI issues through the cable, so I tried to boot a raspberry pi using this extension cable and it works fine. This fact makes me think that the problem is not related to the extension cable but with the SD Card interface of the Zeboard.

       

      Does anyone can help me with this problem ?

      Thank you very much in advance !!!!

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