midi2mqtt

This is a simple bridge between a MIDI device and MQTT. Right now it only supports noteon noteoff poly aftertouch and cc messages.

Getting started

Prerequisites

• Node.js >= 10.13.0 (including npm).
• MIDI device connected and showing up when running e.g. amidi -l
• All pre-requisites from the node-midi package, including the libasound2-dev package if on Linux

Install:

Run sudo npm install --unsafe-perm -g midi2mqtt. Note that you may need to first run sudo apt-get install libasound2-dev to satisfy dependancies of the Node.js midi library.

Start:

First run midi2mqtt --help to see how the program is used.

• You will likely need to specify the MIDI port (-p)
• You can also specify the MQTT topic prefix with -t, including slashes (e.g. -t "home/midi").

If you do not know the MIDI port names on your system, you can simply run midi2mqtt and look for the messages about avaialble MIDI input and output devices.

Simply press ctrl-c to exit the application on the command line.

Example command line:

midi2mqtt -t "house/midi" -u "mqtt://mqtt-server" -p "Midi Fighter 3D 20:0"

Topics and Payloads

Updates from MIDI device to MQTT (read-only)

Topics take the form <topic>/out/<channel>/<type>/<parameter> <value> where <topic> defaults to 'midi', <channel> is the MIDI channel (0-15), <type> is one of 'noteon', 'noteoff', etc., <parameter> depends on type, and <value> is the message payload which also depends on type.

Currently supported topics are as follows: /out//noteon/ /out//noteoff/ /out//poly_aftertouch/ /out//cc/

Commands from MQTT to MIDI device (write-only)

Topics take the form <topic>/in/<channel>/<type>/<parameter> <value> where <topic> defaults to 'midi', <channel> is the MIDI channel (0-15), <type> is one of 'noteon', 'noteoff', etc., <parameter> depends on type, and <value> is the message payload which also depends on type.

Currently supported topics are as follows: /in//noteon/ /in//noteoff/ /in//poly_aftertouch/ /in//cc/

Special-purpose topics

<topic>/connected

Read-only status of the program:

• 1 when program is up
• 0 when the program exits or MQTT disconnects

Starting at boot

You can easily start this program on boot using systemd.

First, as root, create /usr/lib/systemd/system/midi2mqtt.service with the following contents:

[Unit]
Description=Bridge from MIDI to MQTT
Wants=network-online.target
After=network-online.target

[Service]
Type=simple
ExecStart=/usr/local/bin/midi2mqtt -t "midi" -u "http://mqtt-server" -p "MIDI Device Name"
Restart=always
User=<user>
Group=<group>

# Give a reasonable amount of time for the server to start up/shut down
TimeoutSec=300

[Install]
WantedBy=multi-user.target

Note: Be sure to edit the midi2mqtt command line args to match your setup as well as change the User and Group to what the program should run as.

License

MIT © Andy Swing