Tristate Multiplexing

Tristate multiplexing (or Charlieplexing) is a simple to use technique to expand the number of LEDs that you can light from a simple microcontroller. This post explores the concept, and looks at some interesting calculations we can do when thinking about them. I’ve been meaning to get around to writing something of a tutorial on […]

GPIO with sysfs on Raspberry Pi (Part 2)

In my last post on using sysfs for GPIO on Raspberry Pi, I showed you how you can use the sysfs file system to manipulate the state of the GPIO pins. This time, we’re going to explore how to do the same thing programmatically. I’m going to walk you through developing a C library to […]

GPIO with sysfs on a Raspberry Pi

The Raspberry Pi (in case you’ve been living under a rock for the last six-months) is a cheap ($25) ARM Linux computer, primarily designed to be used to help teach kids to learn programming & computer science. It’s also makes a pretty nice alternative to something like a BeagleBone, if you’re looking to play with […]


The MintyBoost is an open-source, small form-factor, USB charger which runs on AA batteries – and lets you charge your mobile phone, tablet or other USB device, without the need for mains power or a computer.  It was designed by one of the leading proponents of the open-source hardware movement, LadyAda – aka MIT Engineering […]