I’ve had an M13 for many years and have partially worn out the switches that control the looper. They work, but not every time. Glitches are often enough to make looping an impossibility. After a bit of research, I’ve found you can control all aspects of the looper via midi, using these CC commands

Record/Overdub 50 0 to 63 = Overdub 64 to 127 = Record
Play/Stop 28 0 to 63 = Stop 64 to 127 = Play
Half Speed 36 Toggles between Half Speed & Normal Speed
Reverse 85 Toggles Reverse On or Off
Undo/Redo 82 Activates Undo/Redo
Play Once 80 Activates Play Once function
Pre/Post 84 0 to 63 = Pre 64 to 127 = Post
Looper Control 86 0 to 63 = Exit 64 to 127 = Enter

The beauty is that issue these commands without entering into looper mode, so all 12 pedals still control effects. You need 2 switches each to duplicate rec/ovr and stop/play and you have to press stop before you can record a new loop, but that’s a tiny issue. I’m now working on a small pedal using arduino to transmit the relevant commands. As ever, the electronics is not the issue, it’s finding a suitable (and cheap) enclosure ;(

See the follow-up post with the relevant midi messages.