Here are some projects I worked on. Newer ones may be on my GitHub account.


A home automation magic wand.


A daisy-chain of electronic shelf labels I made for decorating my office. I wrote a full length blog post about it.


elink: A panel made out of 20 small e-paper displays


A digital hydrometer. It floats on top of a solution and measures its density. It's used to track the fermentation process while brewing beer and wine. I wrote a short Twitter thread about how it works.

sugarboat board sugarboat inside container

Sugarboat inside a plastic container


An open hardware and open source soil moisture and ambient temperature/humidity sensor. It uses Bluetooth Low Energy (BLE) to broadcast its sensors' data. On rbaron/b-parasite.

b-parasite b-parasite in a plant vase


A quick way to add HTML forms to static websites. Just copy the generated <form> element to your website and receive email and Slack notifications on new submissions. A REST API is available for geeks. Access it on

A formbot Slack notification
An example Slack notification.


An open hardware LIR2450 coin cell battery charger. It lives on rbaron/lir2450-charger.

Front Back
Front and back of the printed circuit board.


An Android/iOS app that uses the device's camera for automatically grading multiple choice tests. Live on

SmartGrade scanning SmartGrade exam analysis
Here's the app scanning a single answer sheet and displaying some aggregated stats


A Nintendo NES emulator written in Go. Check it out on rbaron/awesomeones.

dk smb
Donkey Kong and Super Mario Bros. running on the emulator.


Hacking a cheap fitness tracker bracelet. I wrote about the process in this blog post. Source code on rbaron/fitless.

bracelet helloworld
"Hello, world" running on the fitness bracelet


A minimalistic Optical Mark Recognition Python/OpenCV script. It lives on rbaron/omr.

OMR Input OMR Output
On the left, a picture of an answered sheet, used as input. On the right, the output with the automatically recognized answers


An toy implementation of Shamir's secret sharing scheme in zero-dependencies C. Using this, a secret (for example, a password), can be split between n people, so that k people are needed to reconstruct it. It's on rbaron/secret..