This is great: gdsports/midiuartusbh: MIDI DIN to MIDI USB Host Converter allows your USB MIDI instruments to act as traditional MIDI controllers. It uses a Adafruit Trinket M0 to act as the USB host and MIDI output.
I modified gdsports’ design very slightly:
- Instead of using a 74AHCT125 Logic level converter and driver, I used a FET-based SparkFun Logic Level Converter
- Instead of a 5-pin DIN socket, I used a 3.5 mm stereo socket.
And it works!