Emulate an SD card

Someone managed to emulate an SD card with a
propeller in order to send data to a device with a screen,
how could it be a camera or a digital photo frame?
Thanks

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Fisio
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  • 4 Comments sorted by Votes Date Added
  • edited October 2009 Posts: 0Vote Up0Vote Down
    Guess you don't get an answer because it's simply not possible.

    What is done with the SD card drivers is using the SPI mode of SD-cards. That's because SPI mode is the only mode you are allowed to use without paying to the SD card consortium. And without paying you don't get the permission and you don't get the full specs of the SD interface.
    All consumer products which have the SD logo on it support the real SD mode which uses 4 data lines instead of one. This is what you'd have to emulate. And you'd have to emulate it at a clock frequency of 20MHz (if I remember that correctly) which is simply to fast for the propeller.
  • Didn't Rayman do a project like this a while back?

    I'm pretty sure his work-around was to talk to the SD card from a Propeller while the screen wasn't with both connected,
    but only he could tell us for sure.

    OBC

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  • edited October 2009 Posts: 0Vote Up0Vote Down
    I am not sure what kind of speed you need, but it would be possible to use a real SDcard and just swap control of it back and forth between the propeller and whatever device you are controlling.
    There is an article in Circuit Cellar about a year back on a project where the author did that.
    Your limitations are:
    You cannot go much beyond 2MB/Sec with the current drivers
    If you keep writing the same blocks on the SDcard, it will get slower and slower.
    You(obviously) with this scheme cannot read and write at the same time.

    Doug
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