Atto Is a Mini Arduino-Compatible USB Dev Board
BnBe's ATmega32U4-based dev board is not much larger than a microSD card and includes native USB support.
Arduino boards, like the Uno, are great for getting started, but what if you want something smaller… much smaller? For this purpose, it would be hard to beat the Atto, which bills itself as “an incredibly tiny, Arduino-compatible board with USB.” In fact, it’s actually littler than a USB-A dongle, resembling a microSD card scale-wise.
While only 0.5" x 0.8" (12.70mm x 20.32mm) in size, this board doesn’t compromise significantly on features. It packs an ATmega32U4 microcontroller, along with a micro USB port, allowing it to run Arduino Leonardo and Micro sketches and function as an HID device.
The Atto features 11 digital I/O pins, as well as four analog inputs (one shared with digital pin 6), and four of the digital pins can output PWM signals. The board has castellated holes, which saves precious space and enables it to be directly soldered to a PCB or perfboard as a module. One can also solder header pins to it for use on a breadboard.
This piece of hardware looks perfect for use in a custom computer interface, or really any project where you need USB functionality in a tiny package. It’s currently funding on Kickstarter, and can be had for about $9 (£7) plus shipping, with an estimated delivery date of June 2020.