Spoon-Computer Capacitive User Interface

Capacitive touch sensing is an amazing technology that allows a microcontroller to sense someone’s touch on – or even near –an input. The Raspberry Pi Pico, however, requires ~1Mohm resistors that pull each IO to ground in order for it to perform capacitive sensing.

While this isn’t too hard, consider applying resistors for 10 or even 20 pins and the effort involved soon begins to add up. My solution was to build a helper board – the Pico Touch 2 – that takes care of this for you. It mounts 23 SMD resistors between the GPIO pins and GND, enabling you to simply hook up your capacitive input pads to the Pico Touch 2 pins.

It’s an interesting concept, but to illustrate what you can do with it I came up with two demo projects. First I recycled a number of old PCBs, using their formerly +5V copper layer as an input pad that covers most of its surface. I glued three of them onto a piece of MDF. The middle PCB made a great controller for the Dinosaur game as a virtual spacebar. The left and right pads trigger key combinations that switch browser tabs.

I also applied three sets of alligator clips to the RPi/Pico Touch 2 combo. Using the same code as the PCB setup, the spoons could perform Dinosaur game/tabbing once hooked up. These demos were programmed in CircuitPython, and a code swap meant that the spoons could also act as a very simple MIDI controller. It was fun to play, and something I may revisit on the JCo Audio channel.

The Pico Touch 2 is now for sale on Tindie, and I hope people are able to make their own excellent capacitive touch creations with it!