Because our project is an interconnected experience, I decided to use a Raspberry Pi 3 to power the electronic side of the tree because of its built in wifi and bluetooth capabilities and its processing power. The hope was to be able to connect to other experiences over wifi if necessary. The idea was to create something using capacitive touch as the interaction layer between the player and the tree, either using paint or foil strips in a way that was easily understood.
I started by building an example project from the Ultimate Raspberry Pi Handbook, “Turn a banana into a guitar”(1) as a way to get a quick prototype up and to learn how to use the pi. We used an Adafruit Capacitive touch Hat and soldered Female header pins to connect it to the pi, while adding additional male header pins to the GPIO extension part of the Hat to allow us to connect additional devices if needed. We also had to run a previous version of Raspbian for compatibility with the Capacitive touch Hat (as the way that the I2C bus is initiated in newer versions causes an incompatibility issue).
The connection points on the Hat were connected to strips of aluminum foil with alligator clips for testing purposes. My initial tests with this setup and the example code from the handbook felt very natural and responsive.
I also connected an external bluetooth speaker via an audio cable, because we wanted the sound that the tree makes to come through the tree. It’s connected over a cable, because when running python scripts with super user access (which is required when using the raspberry Pi GPIO pins) the default audio output is through the headphone jack.
I was also able to successfully add code to the example project that would turn on an LED connected to the GPIO pin extension of the capacitive touch hat.