extending the distance of an micro SD card reader

Discussion in 'Digital Circuit Design' started by rafi533, Aug 17, 2017.

  1. rafi533

    Thread Starter New Member

    Aug 17, 2017
    2
    0
    Hi,
    I have foxeer legened 1 1080p video camera
    [​IMG]
    and I need the micro SD card to be 90 cm away from the camera.

    I tried to take 2 SD card sniffers like this: (https://www.4project.co.il/imgs/13/product_1334_19165_0x0.jpg)
    [​IMG]
    and connecting them with 90 cm long #24 wires, and to insert 1 side into the camera microSD card slot, and in ther other side i inserted the microSD card itself - but it is not working (seems like the camera is not recognizing it).

    Any ideas? Solutions?

    thank you!
     
  2. RichardO

    Late Member

    May 4, 2013
    2,273
    895
    The SD card uses high speed signals. To get these signals over that distance will require buffers.

    I don't know if a simple solution exists. Maybe others will.
     
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  3. Sensacell

    Moderator

    Jun 19, 2012
    2,424
    802
    At 90 CM, the problem becomes non-trivial, the high speed digital signals get significantly degraded by reflections, losses and lack of solid ground at these frequencies.

    It "might" work if you use twisted pair cable, with every signal wire twisted with a ground wire.
    You may also need a termination network at the cable ends to suppress reflections.

    The next level up would be differential line drivers and receivers, again, a non-trivial design problem.

    Almost impossible without a fast oscilloscope and some high speed design chops.
     
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  4. Papabravo

    Expert

    Feb 24, 2006
    12,279
    2,723
    I take it from the signals on the breakout card, that the card is using the parallel interface as opposed to the SPI interface (which is available on full size cards). Using the SPI Interface would be possible with unidirectional line drivers and receivers. I'm not at all sure about using the parallel interface in this way or how you would turn the data lines around.

    Turns out you have to use the SPI interface unless you've signed the NDA. So yeah -- use unidirectional line drivers and receivers with twisted pairs. Make sure the devices have edges that are as square as possible and also make sure that you have a really stiff 3.3V Power Supply
     
    Last edited: Aug 17, 2017
    rafi533 likes this.
  5. dendad

    Distinguished Member

    Feb 20, 2016
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  6. rafi533

    Thread Starter New Member

    Aug 17, 2017
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