MIDI footswitch

This implements a USB MIDI footswitch on a Raspberry Pi Pico microcontroller. It is configured to control an AKAI MPC X/Live/Live II/One/Touch.

For pictures and details, see the corresponding blog post.

Features

• Presses are debounced
• Each button can be configured to send an additional command when held down. For example, the stop button will send the reset command when held for longer than 1/4 second.

Software

Compiling and uploading with Make

If you want to use this firmware without modification, you can download a compiled .uf2 file in release.zip in the Releases section on GitHub.

Prerequisites

• Raspberry Pi Pico SDK
• cmake
• OpenSCAD (if 3D printing the hardware)

Build

In the software directory, run cmake to generate Makefile

PICO_SDK_PATH=/path/to/sdk cmake

To build the code

make

To program the device:

• Hold down the button on the Pico board while plugging in the device.
• Copy the .uf2 file to the device.

Hardware

Four footswitches share a common connection to ground (pin 3). The other terminal of each is connected to GP0-GP3 (pins 1, 2, 4 and 5) respectively. The code can be adjusted for more or fewer switches.

BOM

• Hammond 1590XX enclosure
• 4 momentary push-to make footswitches
• Raspberry Pi Pico
• Panel-mount USB B socket micro USB cable
• 4 M2 × 5mm pan head self-tapping screws

Switch connections

3D-printed components

If you want to use these without modification, you can download generated STL files in release.zip in the Releases section on GitHub.

OpenSCAD models for a bezel to surround the socket, a bracket to hold the microcontroller, and a couple of tools to help line up the switches and feet are included in the hardware directory. To build the STL files, run make in the hardware directory.

The parts are as follows:

• foot-aligner.scad -- a corner bracket to facilitate aligning sticky feet consistently with the corner of the enclosure.
• pico-mount.scad -- a frame that is held in place by the footswitches, to which the Pico may be screwed with M2 × 5mm self-tapping screws.
• switch-spacer.scad -- helps with offsetting the lower nut on footswitches so that they protrude a consistent distance above the top. May require variation for your switches.
• usb-bezel.scad -- a bezel to allow fitting the USB B socket by drilling only round holes. May require adjustment for your socket.
• usb-drill-template.scad -- drill straight through this to get consistent, even holes for mounting the USB socket. May require adjustment for different sockets.