Four jumper wires with white heatshrink on them, labelled VCC, SCL, SDA and GND

The Connector Zoo: I2C Ecosystems

I2C is a wonderful interface. With four wires and only two GPIOs, you can connect a whole lot of sensors and devices – in parallel, at that! You will see I2C used basically everywhere, in every phone, laptop, desktop, and any device with more than a few ICs inside of it – and most microcontrollers have I2C support baked into their hardware. As a result, there’s a myriad of interesting and useful devices you can use I2C with. Occasionally, maker-facing companies create plug-and-play interfaces for the I2C device breakouts they produce, with standardized pinouts and connectors.

Following a standard pinout is way better than inventing your own, and your experience with inconsistent pin header pinouts on generic I2C modules from China will surely reflect that. Wouldn’t it be wonderful if you could just plug a single I2C-carrying connector into an MPU9050, MLX90614 or HMC5883L breakout you bought for a few dollars, as opposed to the usual hurdle of looking at the module’s silkscreen, soldering pin headers onto it and carefully arranging female headers onto the correct pins?

As with any standard, when it comes to I2C-on-a-connector conventions, you would correctly guess that there’s more than one, and they all have their pros and cons. There aren’t quite fifteen, but there’s definitely six-and-a-half! They’re mostly inter-compatible, and making use of them means that you can access some pretty powerful peripherals easily. Let’s start with the two ecosystems that only have minor differences, and that you’ll encounter the most! Continue reading “The Connector Zoo: I2C Ecosystems”

Quick-Swap Socket For Stemma QT Experiments

[kmatch98] shares a quick hack with us over at – a 3D-printed socket for Adafruit Stemma QT-based I2C modules. Since Adafruit has standardized the dimensions for their Stemma QT boards, it’s possible to make a socket that would fit many different sensors at once, where the board just slides in.

This reminds us of sci-fi datadisks, or, thinking of something more grounded in reality, game console cartridges – except that here, the fun you’re having is from exploring all the different devices you can get to speak I2C. To make such a socket, you only need to 3D-print two plastic parts, put a JST-SH plug between them, and screw them together – if you want to modify these to your liking, .f3d sources are available. Now you no longer have to use fingernails or tin snips to take the JST-SH plug out of your modules!

[kmatch98] is no stranger to sharing his projects on with us, and we’ve covered some of his larger projects before, like this CircuitPython-powered cyber-duck cyberdeck, or the 3D-printable Maypole braider machine!