Introduction

MIDI is a protocol that was invented to send Note-On/Off and Controller values between synthesizers connected by a serial-port interface. Because of its generality in the numbering of notes and controllers, MIDI has found many other uses besides synthesizers.

This program midi2gpiod was designed for a RaspberryPi. It watches a specified MIDI port and converts Note-On/Off messages to GPIO on/off commands using the libgpiod library. By default, the program watches for MIDI messages arriving from McLaren Labs' rtpmidi program. (See https://mclarenlabs.com/rtpmidi. This allows GPIO pins to be "played" by sending MIDI commands over a network.

But you could also "play" GPIO pins directly by attaching a MIDI keyboard directly to the USB port of the Raspberry Pi.

This program will probably also work on other devices that support the libgpiod library, but it has not been tested on them.

Requirements

To compile the program, the following must be installed.

• $ sudo apt-get install libasound2-dev
• $ sudo apt-get install libgpiod-dev

Usage

$ midi2gpiod

Watch for MIDI notes emanating from port rtpmidi:0 and turn GPIO pins 25,26,27 on and off when middle-C, D and E are played on the keyboard.

$ midi2gpiod -v -p midikbd:0

Watch for MIDI notes from a device named midikbd and convert to GPIO on/off commands. Log relevant MIDI messages received to stdout.

Run MIDI2GPIOD as a Service

This program can be configured to start whenever the Pi reboots by making it a service. The included file midi2gpiod.service is suitable for use with systemd.

To use: first copy midi2gpiod.service to /etc/systemd/system as user ROOT. Then, type these commands to register the service with systemd.

$ sudo systemctl daemon-reload

After this you will be able to start the service with

$ sudo systemctl start midi2gpiod.service

To make the service survive a reboot and automatically restart, use the "enable" command.

$ sudo systemctl enable midi2gpiod.service

You can see log messages in Syslog. Have a look here.

$ tail -f /var/log/syslog

Designed to work with IOTRELAY

Have you ever wanted to control 120 Volt AC lights or appliances via MIDI? This program combined with the IOTRELAY is the easiest way to do that.

See https://iotrelay.com.

An IOTRELAY unit is controlled by a single GPIO pin. It has four AC outlets:

• one is always ON
• two are normally OFF, but is turned ON by the GPIO pin going HIGH
• one is normally ON, but is turned OFF by the GPIO pin going HIGH