The Feather M4 Express will show up as a USB MIDI device when connected to a computer. MIDI software instrument with capabilities to create external MIDI out instruments will need to be setup in order to get the solenoids to fire.
Mac OS – Audio MIDI Setup
The Feather M4 Express will should up in the MIDI studio window in the Audio MIDI setup application. Right-click Edit device to open the properties window. There you can change the device name and ports. Nothing needs to be changes here, just FYI.
Logic Pro X – External MIDI Track
In the track list, right-click and choose "New External MIDI Track". This allow you to assign the Feather M4 Express to a MIDI track. Using a MIDI track allows you can create musical MIDI notes.
MIDI Track Port
In the Inspector panel, under the Track section, select Feather M4 Express from the Port dropdown. This will assign any MIDI notes in the track to the Feather M4 Express.
MIDI notes can be played live using your computers keyboard. In the top menu, select Window > Show Keyboard. Use the interface to trigger music notes, change octaves, velocity, etc. This is a great way to test solenoids and play live.