Breakout Board for DOSonCHIP FAT16 FAT32 uSD Module

Replacement: None. There is no suggested replacement for this item. This page is for reference only.

This is a ready to go module that utilizes the DOSonCHIP FAT16/32 IC with accompanying micro-SD socket. Excellent evaluation board for the DOSonCHIP™ silicon or for file storage, simple datalogging, and high speed API datalogging! Uses a simple UART or SPI interface. Low 5mA current consumption.

DOSonCHIP is very powerful and supports larger SD cards (up to 32GB) but requires a more complex command structure. For simple data logging, we recommed OpenLog for beginners.

The DOSonCHIP embedded file system and SDHC/SD/MMC controller makes it easy to add up to 32GB of storage to your project without adding software complexity (OS Not Required). Add flash storage for data logging, configuration, audio recording, web serving, and more with this high speed, low power IC. DOSonCHIP is a drop-in solution with UART and SPI interfaces and included host-side ANSI C code—just fill in the appropriate definitions for your host communications port (or leverage the included bit-banged SPI code). The open source interface code provides comprehensive file system access functions that will be familiar to any C programmer. Commented sample code that demonstrates how to use all of the functionality of the DOSonCHIP is provided too. Adding high-capacity removable storage to an embedded project couldn't be easier!

We now have ICs with v2 firmware. Compatible with SDHC (up to 32GB!) and 60 times the speed of the original version.

If hardware flow control is not needed, tie CTS to ground.

microSD card sold separately below.

**Dimension: **1.0x1.45"


  • Integrated real-time clock for current date & time and file-stamping
  • Low power consumption
  • 2.7V to 3.3V operation with 5V tolerant I/O
  • Active current 5mA @ 3.3V (typical)
  • Shutdown current < 0.1µA
  • 0.8mm height—small enough to mount under many SD sockets
  • 24-pin QFN package
  • Simplified pinout matches card socket layout
  • Minimal external passives required for low total system cost
  • Host Interface
  • UART with autobaud detection
  • SPI bus
  • I2C/SMBus (not enabled in current firmware)
  • FAT32 & FAT16 compatible
  • 4 simultaneous files open


Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • unfortunately, not everything in this world is "plug & play"...enjoy the challenge...roll up your sleeves and get down to some serious coding issues....

  • Does anyone know a tutorial were the PyxiOS SD library gets implemented to control this little and hell bound beast?
    I only need to log simple timestamps and this thing has already stolen many days of my live.

    • Hi, I am sorry, but at this time there are no tutorials for this board that Sparkfun has written. We will add it to our list of future tutorials. And hopefully we can get one done in the future, but there is a whole bunch of items that need tutorials, so I can't promise anything. We have supplied all of the information that we have available for this board above.

      • So...a few months have passed by now... any chance there is a not so detailed tutorial coming soon? I only want UART communication and the challenge is still above my current ability. Does it help if a say "please"? Please?

        • The product is retired and we don't support retired products. Check the openlog, it's much easier to use.

  • Pyxis OS for the Arduino uses this module to run compiled apps from a uSD card. You can get the library free by downloading Pyxis OS from

    What is the support status of this product? No "contact /support" facilities obvious at their website, and their their latest news is dated FEB-20th, 2009!
    I echo all gripes below. I need to interface this breakout to an AT128 SPI. I've spent two days poking it with a scope and reading everything I can find on the web, including scrutinizing their driver code.
    I'm suspecting that the interface has changed since the initial release and initial documentation, and that it can no longer be driven directly from a terminal interface, but only from an API.
    Wearables aka DosOnChip please get in touch with me at( and then I'd be happy to reconsider/withdraw these comments.

  • It looks like the Documents section is missing the CD17B10 User Guide which outlines the commands used to communicate with the DOSonCHIP device.
    Is there any way you could post that?

  • yeah should've read the comments about this product.
    there's a lot of code to sort through to get things running correctly and the source code is there but not as well wrapped up as it could be...
    so i agree with the others on here, don't use this unless you wanna take the time to understand all the code, then write wrappers to take care of the little issues to make one file

  • Have to agree with @ticked -- this product is not simple to use or interface in its new v2 API interface. If they added backwards compatibility, that would be fine, but because they have fully embraced the API interface, with the only documentation the API example code, it's very difficult to understand without a lot of coding experience.
    If you're looking for something simple and a serial interface, try:
    If you're looking for something simple w/ an SPI interface, you may want to try interfacing the card directly, and using something like uFat2:

  • Unless you have some sort of computer engineering degree I would avoid this product. Absolutly no documentation what so ever. "Datalogging is now as easy as sending 'md CHAT' to make a directory!" hmmmmmmm

  • I need a simple datalogger then can record a timestamp and the id of a rfid tag using one of your rfid reader?s.
    Is it possible to do that using this board?
    what else do I need? tks

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