Bare Conductive Pi Cap – photograph by Adafruit
Bare Conductive’s Pi Cap is an add-on board for the Raspberry Pi that plugs into the GPIO pins. It provides the following features:
- 12 conductive crocodile clip-compatible connection points
- High quality audio output via a 3.5mm jack
- A user-programmable RGB LED
- A tiny button
- 7 unused GPIO pins broken out
- A prototyping area
It is compatible with any of the 40-pin Raspberry Pis and comes with extensive programming libraries written in Python, C++ and NodeJS.
Bare Conductive were kind enough to send me one of their Pi Caps and I’ve spent a few hours trying it out. I have to say I’m very impressed. It’s an interesting mixture of hardware features, certainly. In fact, at first glance the 3.5mm jack in particular seems like an odd addition. However, a closer look at some of the example scripts provided gives you a glimpse at the ways you could use the jack in combination with the conductive inputs.
Installing the software is an easy process – a simple apt-get command and another setup command after that – and they provide great instructions online to get you going from first principals such as burning an operating system image onto an SD card to using the tutorial script provided. Speaking of which, the tutorial script is ingenious – it’s a text-based to some of the examples provided and you can see them working by touching the capacitive inputs. This gives you an ‘instant win’ in terms of seeing the hardware working. The example code is well thought-outand useful and it shouldn’t take much for a beginner programmer to unpick the code and bend it to their own uses.
The capacitive inputs work by touching the pads with your finger, or by connecting up conductive objects (bananas come to mind!) to the inputs. I used conductive ink to draw a line on the back of an envelope and connected a crocodile clip from the pad to the ink. That way, when I touched the ink the conductive input registered the touch. Just the job for simple experiments.
Breaking out the unused pins is, of course, a winner for any hacker of hardware, so this is good to see. 7 GPIOs should be enough to add LEDs, switches, even a buzzer and the prototyping area keeps everything neat. The addition of a tiny button on the side is a bit useless, but I guess good if you need it. The only negative thing I can say is that the button is on the inner side of the board so you need a pencil or something to reach it past the USB ports.
The 3.5mm jack for audio provides a high-quality line-out output from the Pi. As I’ve said before, this may seem a strange addition but they provide an example of using the touch inputs to play sound, so turning the Pi Cap into a musical instrument with decent quality audio is a real possibility.
The price, £28, is a bit steep for an add-on board for the Pi, however there are such a lot of features, and the board is so versatile in terms of what you can use for inputs that I think it’s well worth it.
Thoroughly recommended.
You can buy the Pi Cap from Bare Conductive or The Pi Hut for around £28.
