This tool for Raspberry Pi monitors MIDI connections, and displays them in a OLED screen.
The grid shows MIDI outputs as rows, and MIDI inputs as columns, ordered in the same way, like a correlation matrix. A cross represents a connection. There are 4 ports max, as that's the max USB ports the RPi has.
Clone or download the repo as zip package, and run
sudo make install
In my case I'm using a SSD1306 128x64 display, and code is scaled for it.
Enable I2C,
sudo raspi-config
Go to Interface Options -> I2C, and turn on. Then connect your OLED screen using the I2C pins. You can read the pinout, and how to verify your device address here.
If your I2C address is different from 0x3C, run
sudo systemctl edit midimatrix
and it will open an editor, add this,
[Service]
ExecStart=/usr/bin/midimatrix --oled-i2c-address=03E
save, and restart the service
sudo systemctl daemon-reload
sudo systemctl restart midimatrix
You can wire a button to navigate, and make connections. Default pin is GPIO 26. Follow the steps above to customize the startup params.
Press to move forward, and hold to connect/disconnect ports.
midimatrix --help
You can just use the aconnect ALSA utility,
# List devices
aconnect -l
# Connect A to B
aconnect A B
# Disconnect B from A
aconnect -d A B
# Disconnect everything
aconnect -xOr install amidiauto or amidiminder, in which you can define rules to connect devices on startup and reconnect devices when available.