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Is it hard to interface a compact flash / secure digital card / etc. with the S — Parallax Forums

Is it hard to interface a compact flash / secure digital card / etc. with the S

dasdas Posts: 3
edited 2005-10-13 03:09 in General Discussion
Hi,
I was buying a 1GB secure digital card for my digital camera and thought, "·Hey, would it be possible to interface the SD card with the Stamp so that I could store· 1GB of code or data on it"?

Does anyone know if there is an interface guide / chip that a consumer can purchase to do this?

I was shopping for EEPROM's and they· usually come in small sizes (e.g. 64kb, 128kb) and cost about as much as a 512MB SD card.

Thanks,
Dean

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-10-12 18:22
    Hello,

    ·· This question seems to come up at least once per month.· If you search the forums for the word flash, you will find a bunch of other threads on this subject.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-10-12 18:51
    Is it possible? yes
    Is it easy? no

    There are many complications when interfacing with MMC (SD cards support MMC SPI interface), the biggest issue is that the smallest write block the things handle is 512 bytes, more data memory than a stamp (or even SX) can handle internally. This is my current project, the spec sheet I am using as a reference is http://www.sandisk.com/pdf/oem/manual-rs-mmcv1.0.pdf·and I find the specs a bit daunting, even though I am a·rather seasoned programmer. I have confidence I can make the thing work (Ill be using a FRAM memory to temporarily hold data until a 512 block is prepared), but I fully expect to experience many "gotcha's" before I get the thing to work properly. Right now Im still in the preliminary stage, I have the basic hardware components but need to buy some more before I can get a functioning hardware setup.

    There is a pre-rolled package you can get that provides an interface to them and formats the disk in a FAT compatible method so you can access the data on a PC as well, but its in the $100 price range. Search the forums as Chris suggested to find the name of the module, because I always forget the name of it. (after a quick search it's called ALFAT)

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    Post Edited (Paul Baker) : 10/12/2005 6:54:03 PM GMT
  • SPENCESPENCE Posts: 204
    edited 2005-10-12 20:32
    ALFAT/GHI/SPI/I2C/IDE Developments
    http://www.ghielectronics.com

    http://www.ghielectronics.com/ALFAT DEV.htm
    ABOUT $90 MAJOR PRICE DROP

    http://www.ghielectronics.com/ALFAT-SD.htm
    ABOUT $50


    73
    SPENCE
    K4KEP
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-10-12 20:36
    Thanks for the price update SPENCE, they have gone down in price since the last time I looked.

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  • Kevin WoodKevin Wood Posts: 1,266
    edited 2005-10-12 20:56
    I posted a link on the SX forum for a Hitachi document that gives some info on embedding a microdrive with an 8051 mcu. There is a brief interface schematic, and about 22 pages of 8051 assembly code. It looked like it would be a good source of info for somebody that might want to read the code and get some ideas for an SX48/52 project.
  • David BDavid B Posts: 592
    edited 2005-10-12 22:47
    I have managed to get some data written to an MMC card from an SX28, and yes, it is hard.

    Like Chris says, search around and you'll find lots of info, including my code in a response to an earlier similar question.

    I did find that once a write is initiated, there is no problem with feeding your 512 bytes of data in as slowly as you want; the MMC/SD clock has no lower speed limit. So there should be no need for any sort of temporary data store.

    David
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-10-13 03:09
    David B said...

    I did find that once a write is initiated, there is no problem with feeding your 512 bytes of data in as slowly as you want; the MMC/SD clock has no lower speed limit. So there should be no need for any sort of temporary data store.
    David you are correct that you can slow things down·when feeding data to it, but there are some caviats to it, which don't apply under normal circumstances but under certain·conditions there is the potential of data loss. But I wont go into the particulars since it will stray a little off topic unless someone is interested in the details.

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    ·1+1=10
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