The Tomu by Sutajio Kosagi is quite a delightful board with a microscopic profile. At only 13mm long, this fully open-source development board is perfect for USB-oriented projects and noodling around with a Silabs Gecko EFM32HG309 ARM processor. The Tomu is quite spartan with only 12 core parts in its design, including two buttons and LEDs. Its ultra tiny profile is great for discrete applications like a U2F key, media buttons, or any particular project where a small profile is a must. The best part is that the Tomu has a native USB bootloader which means you can reprogram it directly without any specialized tools. Simply plug this sucker in, follow the quick start instructions, and start developing! Easy peasy.

If you know about Novena, a previous project of Sutajio Kosagi, then you are probably familiar with the philosophy behind any of their designs. If not, buckle in and imagine an anti-consumer consumer landscape where hackers frolic freely, modding systems left and right. This is open hardware and it has an air of transparency that lends itself towards facilitating the DIY in all of us! It’s absolutely addicting, inspiring, and fantastic! In continuation of this O.G. legacy, Kosagi provides all of the Tomu’s design files on their GitHub with concise documentation on how to build your own. In my opinion, this is the best feature of the Tomu and it empowers makers to be creative without limitations. In the spirit of hardware hacking and software development, Tomu takes the cake!

However, despite its strengths, Tomu does have some notable pitfalls. I found the prebuilt unit expensive for the applications advertised. At around $30 per unit, it’s worth weighing your options with other small factor development boards. For example, the Digispark USB board is slightly larger with significantly lower specs, but costs a mere $2-8 per unit (search eBay). This board can function as a simple password manager, a rubber ducky, and other fun shenanigans. If you’re not planning to build the Tomu from scratch and your project does not require some of the nicer features, then why pay for a forklift when maybe all you need is a dolly?

The stock 3D enclosure was also oddly cumbersome and flimsy. While it secures the Tomu, there is no way to attach a lanyard to it. I found it hard to slot the Tomu in and out of my computer, had narrow access to the buttons, and the board was also prone to disappearing on me. This was distracting and anxiety-inducing enough for me to want to redesign and 3D print a new enclosure to meet my needs.

Regardless of its quirks, the Tomu by Kosagi is still novel and worthy of exploration! As an avid fan of open hardware, I look forward to seeing more boards from the Tomu family. For the maker that loves being able to hack everything on a board, the Tomu is a great development board to play with.