Finding out the communication protocol for communicating with SD cards is not easy – the specification is not available for free, and relies on a proprietary 6-wire bus. However, SD cards can also be accessed via SPI…and this is what the following application note from Dallas Maxim covers:

It starts of by looking at the electrical interface and goes on to the actual communication protocol, covering special commands, speed limits and other interesting stuff.

If you ever need to use an SD card in a device you built yourself, start your research here…it will pay out!

Related posts:

  1. Smart Card Interface Fundamentals
  2. Accessing SD cards with a microcontroller
  3. Emulating Li-Ion batteries with a NiMH cell
  4. iButton overview
  5. New Analog/Digital converters from Dallas Maxim

4 Responses to “Accessing an SD card via SPI”

  1. You already wrote about this:
    Besides, the SD-card association provides a simplified physical layer interface document.

    It actually covers SDHC as well, but not SDIO (and I think not any of the DRM stuff).

    You still need to license it from them if you actually use this

  2. There is lots of this, try google “SD card interface library”. Example:

  3. Hello Guys,
    thank you all for your comments!

    Best regards
    Tam Hanna

  4. thank u

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