The Circuit

The Proto Board

The FeatherWing Proto board is great for adding on a small audio output circuit, as well as connections for the STEMMA QT ports over I2C, joystick wiring, and the reset and enable switches.

The schematic below shows these connections as they relate to the Feather board, but you'll make them on the Proto board and rely on the FeatherWing Tripler to connect those points to the Feather.

The Proto Board

Following the schematic above, as well as these photos, solder the parts in place for the:

  • audio output RC circuit (resistor capacitor circuit for removing noise from the audio)
  • joystick wiring (note the use of pin D6 as common joystick switch ground)
  • headers for the enable and reset switches
  • STEMMA QT/Qwiic connector to SDA, SCL, 3v3, and GND.

The Feather Tripler

Add headers and M2.5 nylon standoffs to the Feather Tripler as shown here.

Insert the MIDI FeatherWing (with either DIN-5 or TRS plugs on it, your choice) to the Tripler, followed by the Proto FeatherWing and the Feather M4 Express.

Fasten the boards to the Tripler standoffs so they don't wiggle around when inserting cables later.

LED Arcade Button STEMMA QT Boards

To use the four LED Arcade Button boards on I2C they must each have a unique address.

You will cut the traces on three of the boards to set them.

Set them to:

  • 0x3A (default, don't cut any traces)
  • 0x3B -- cut trace A0
  • 0x3C -- cut trace A1
  • 0x3D -- cut traces A0 and A1

Then, wire them to each other in order from left to right using 100mm STEMMA QT cables.

Arcade Button Wiring

Plug two sets of quick connect cables into each arcade button -- one for the switch, the other pair for the LED.

The polarity doesn't matter for the switch tabs (these are the ones protruding from the gray plastic switch base), however, you must connect the - and + properly for the LED to work. These are marked both on the Arcade Button board LED ports and on the molding of the switch base.

To avoid confusion, I marked these wires in advance using heat shrink tubing. I also used heat shrink to order each set of four buttons yellow, red, green, blue, as shown here. This type of organization helps immensely with wiring things properly and later troubleshooting!

Reset and Enable Button Wiring

I decided not to wire the LEDs of these switches, instead wiring only the switches. Polarity doesn't matter.

Remember, the yellow momentary switch will be plugged into the Feather's Reset pin, and the green toggle switch into Enable.

This guide was first published on Jan 26, 2022. It was last updated on Jul 23, 2024.

This page (Build the Arcade Synth Circuit) was last updated on Mar 08, 2024.

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