My connection are as follows:

• Midi Keyboard → Unit MIDI MIDI_IN
• Unit MIDI MIDI_OUT → USB MIDI adapter MIDI IN
• Unit MIDI Audio OUT → 3.5 mm mini speaker
• USB MIDI adapter USB → PC
• PC → M5Stack ATOM type C
• M5Stack ATOM groove → UNIT MIDI groove

Midi UNIT is running micropython and a midi synth module which I translated from arduino to micropython.

This is what I have tried:

1. When in bypass mode, the keyboard sends events that can be caught by a midi usb device and forwarded to a PC.
2. The PC can send serial commands (via a M5 atom grove port) to the midi device and these are synthesized and played to audio out.
3. When in separate mode, no midi events are synthesized and played on the audio out.

Questions

Is this a hardware limitation, or is it possible to configure midi in → audio out somehow to get sound without a controller connected to the groove port?

Alternately, is it possible to catch the midi input events through the groove port and then forward these back to MIDI Unit to be synthesized to AUDIO_OUT?