To make the UNTZ wireless, we will need to replace the Arduino Leonardo from the UNTZtrument guide with a 32u4 or M0 based Feather Bluefruit LE (seen above). Because of this change, we will need to make a couple small modifications to the case, and add a battery.

Marking New Mounting Holes

The first thing we will need to do is to drill three new mounting holes for the Bluefruit Feather. To do this, I took the bottom plate from the UNTZ case and lined up the USB port of the Feather with the spot where the USB port of the Arduino Leonardo would normally sit. I then pressed on the Feather to make sure it wouldn't move, and used a felt tip marker to transfer the Feather mounting hole locations to the bottom plate.

Drilling New Mounting Holes

Next I used a 1/8" (~3 millimeter) drill bit to drill new mounting holes in the bottom plate of the case. The mounting holes on the Feather are 0.1" diameter, but I wanted to make sure there was extra wiggle room since I was drilling by hand.

Wiring Changes

Follow the original UNTZtrument guide for assembly instruction for the four or eight trellis panels that make up the UNTZ or HELLA UNTZ kits.

The SDA, SCL, GND, and power pin connections are in different locations on the Leonardo vs the Feather. Refer to the pinout diagram and the wiring diagram below for the locations of the pins on your Feather Bluefruit LE.

I used 26 AWG silicone cover stranded-core wire to connect the Feather to the Trellis grid, which made it easy to assemble the case. Solid core wire works as well, but it is not nearly as flexible. The increased flexibility makes the case easier to assemble.

Here are the connections that you will need to solder using your choice of wire:

• Trellis SDA -> Feather SDA
• Trellis SCL -> Feather SCL
• Trellis GND -> Feather GND
• Trellis 5V -> Feather 3V

You will also need to attach a battery to your Feather, and secure it to the bottom plate in the UNTZ case. I used gaffers tape to secure the battery, but duct tape or any other similar tape should work.

No futher hardware modifications to the UNTZ kit are needed for BLE MIDI support. Follow the UNTZtrument guide for additional assembly instructions. Next, we will look at the Arduino libraries needed for UNTZ Bluetooth LE MIDI communication.