The Fomu: An FPGA That Fits in Your USB Port

Alasdair Allan
2 min readDec 10, 2018


UPDATE: Originally called the “Tomu: FPGA,” the Fomu had a name change when the project went live on Crowd Supply. So just to try and keep things tidy we’ve gone ahead and changed the name of the board throughout the article.

Just under a year ago, Tim Ansell released the Tomu — a tiny Arm micro-controller board that fit inside your USB port. Built around a Cortex-M0+, the Tomu bill of materials of the board literally consisted of just 12 parts, including the PCB. Now Ansell is back, this time with an FPGA.

The Fomu. (📷: Tim Ansell)

The Fomu is based on a Lattice iCE40UP5K with 5k LUTs and DSP tiles, along with 128KB of RAM and 2MB of Flash. It also has a single RGB LED, and like the original Tomu, two capacitance touch buttons, plus it still fits inside your USB port.

The Fomu front (left), and back (right). (📷: Tim Ansell)

Designed in collaboration with Luke Valenty, who is currently building what I’d consider the next generation of maker FPGAs, the Fomu has a fully open source toolchain. Capable of running a soft RISC-V core, it is completely compatible with FμPy which is a MicroPython port to run on FPGA using Migen+MiSoC and LiteX, allowing FPGA gateware and soft CPU firmware development in Python.

A guide to using Python to conquer FPGA video systems. (📹 Crowd Supply)

In other words, if you’re interested in getting started with FPGA, this could well be a good entry point. The Fomu isn’t available yet and there isn’t any pricing information, but the project should hopefully soon be live on Crowd Supply.

UPDATE (12/9): The Fomu is now live on Crowd Supply, costing $39, with free shipping inside the United States, and an additional $5 for word wide.

An FPGA board that fits inside your USB port. (📹 Crowd Supply)