Ultrasmall Arduino

[Fabio Varesano's] new Arduino compatible board packs a full power punch in a ultra compact layout, measuring at 20.7×15.2 mm, the Femtoduino is probably the smallest 328 based Arduino compatible board around. Most of the staples are present, an QFN atmega328, an MIC5205 low dropout regulator good for a couple hundred milli amps, 16MHz ceramic resonator, reset, power indicator and pin 13 LEDs, but you will need to provide your own serial connection (FTDI, MAX232 etc) and another AVR programmer to get the Arduino boot loader onto the chip.

Since the board is small (smaller than a pro mini) it is not directly breadboard friendly. Even though the hole spacing is 0.05 inch, the size is large enough for “normal” wire to fit into fine, if you wish to use 0.1 inch spacing there is a handy break out board you can make where the Femtoduino just snaps in.

Everything needed to make one of your own is provided on the website, schematics, kicad files, bill of materials, Gerbers for both the board and the breakout board, though we would like to see this as a pre-made board soon, join us after the break for a video and see why.


  1. Jac Goudsmit says:

    I just caught myself drooling :-)

  2. CutThroughStuffGuy says:


  3. iToast says:

    Awesome but how much will it cost?

  4. Emanuele says:

    In Italy, Arduino is a fever.

    Mr.Banzi hes designed it, Varesano re-design it,
    our blog started a contest Febbruino (Arduino gratis>) and everyone love it!

  5. biozz says:

    finally i can stop deadbugging arduinos!

  6. mad_max says:

    @MikeJ if you ask nicely, a mod might delete it for you…

  7. 133MHz says:

    It reminds me of PlayStation 2 modchips. Now if somebody would port Matrix Infinity to the Atmega328… ;-)

  8. FightCube.com says:

    This is great, but not really good for prototyping since it is on 0.05″ spacing. As the creator states it was meant to be used in the final assembly of a project. So what it needs is a programming board made from pogo pins, and the perfect prototyping platform for this module would be a SMT grid on the bottom side similar to Surfboards but SO pitch or smaller.

    • Fungus says:

      FightCube.com says: “This is great, but not really good for prototyping”

      Wouldn’t you prototype with an Arduino Uno? This isn’t meant for prototyping, it’s for people who need the smallest/lightest possible Arduino-Uno compatible board.

  9. Cool! says:

    You lament that is not a protoboard piece, but there are already many many such ‘duinos you can buy… why ask for 1 more?

    As noted, this is a deployment board however it CAN adapt to a prototype .1 pin. So you get the best of both worlds, actually. I’m not sure what you are missing here..

    I’d like to see these in production, so they are cheap and available (soldering something this small is not my idea of fun…. but programming it would be!) :-)

  10. Dave Nuebury says:

    All I can say is.,………

  11. CutThroughStuffGuy says:

    This is great to take a concept that has been prototyped on a normal Arduino and put it into production. I plan on doing something similar with a whole host of products. Get it operational then put it in production on a smaller, less expensive platform but retain the exact same functionality and modularity. THIS to me is one of the major advantages of the Arduino platform.

  12. CutThroughStuffGuy says:

    What this solution needs are snap in pins or some other mechanical connection that are reliable enough (and small enough) to be machine built (so they are cheap) but once you snap them in, they stay connected and are reasonably as secure as soldering. That way, you can quickly turn these into a final production part. Snap the sensor and output array on – hook up power and embed away.

    Otherwise, you wind up having to hand solder these – and that’s no fun unless you work for $0.40 per hour in China and even then the fun part is debatable.

  13. @Cool! – Yes it’s NOT for prototyping because if it was it wouldn’t be so small. Using an adapter to turn it into a Arduino Mini is ridiculous, just prototype with the Arduino Mini, or any other number of bare bones solutions. If you use an adapter, you have to solder headers into the Femtoduino, and then when you are done prototyping you now have headers soldered into it which may not be desirable for your end application. This is meant for final integration on a small scale (think – wire it directly in… no headers), and can be somewhat aided by my previous suggestions.

  14. Jan D says:

    Even with the break out board it is among the smallest Arduino’s I have seen. Very nice!

  15. o says:

    Even though it’s an Arduino, in this form factor, it’s extremely useful.

  16. WestfW says:

    1.27mm spaced pins are a real pain, but the pins really are the limiting factor for such things.
    Maybe 0.07inch (“Shrink DIP”) spacing? You can get machined sockets in that size, allowing one to continue the rather questionable Arduino tradition of plugging wires into connectors not designed to hold wires…

  17. Shad says:


    Smaller, but it does not have all the pads…

  18. Koolguy007 says:

    Now can they make it smaller?

  19. it still is just an ATmega328 on a breakout board.

    • brome says:

      Completely agree. Build looks nice, it even has regulator like other arduinos, but for me difference between arduino and “controller on a breakout board” is that i can plug arduino in usb without much needs like external programmer. Not that i doesnt have that one – but what about those who doesnt? There are also things like Teensy 3.0 in similar formfactor if the size is what you look for in this project (and it is usb-enabled). Yes, we shouldn’t compare them but what the hell.

  20. Thanks hackaday editors for posting about my Femtoduino project.

    Thanks everybody for liking it and giving your suggestions. Much appreciated.

  21. moo says:

    How much? Because size does matter :)

  22. Volfram says:

    Not a huge Arduino fan, but I would definitely buy one or two of these to play with.(with breakout board, of course.)

  23. lwatcdr says:

    Wow I think this may be small enough for a mini-brute sized data logger for model rockets.

  24. Phil Burgess says:

    If the layout can be tweaked just a couple of millimeters narrower, this could fit inside a hollowed-out LEGO brick.

  25. colecoman1982 says:

    I wonder if they could shrink it down more by going with a multi-layer PCB; putting most of the components other than the processor on the back of the board; and wrapping some of the pads around onto the fourth side.

  26. @colecoman – Yeah technically it can be as small as a 32 pin QFN chip. Just deadbug one of those! However, you’ll be hella-pissed trying to solder connections to it.

  27. Alex Alnbino says:

    If anyone still wants to buy a femtoduino, you can buy one at http://www.femtoduino.com

  28. Leif Burrow says:

    I’m not sure I understand the logic behind building an adapter board to breadboard something like this. It’s just a 328 right? If you want to prototype it then all you need is DIP chip and a resonator (or crystal plus caps). Electrically what is the difference?

    Later, at final build time, if your final application calls for actually using a form factor this small, then you get a femtoduino. Although.. actually.. if you need that kind of miniturization you are probably better off designing and having a custom board made that includes both the 328 and all your other components that aren’t part of the Femtoduino. Otherwise you are just losing space wiring pads on one board to pads on another. Put it all one one board and both the pads and wires are unnecessary.

    The more I think about it, I can’t think of an application where a femtoduino makes any sense.

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