Here’s the Arpeggiator made by Klaus Onnen. Pretty clean! 😀 Thanks to him for sending me these pictures, that is super nice.
Also I discovered this upgrade of my MIDI looper : http://slazzarotto.free.fr/midilooper.html
Everything is explained in French, but basically this upgrade is 4 notes polyphonic & brings note length recording, which is awesome. This one is made with a Arduino Mega though, because the Nano doesn’t have enough space to store all the notes available.