The testing characters in this unit works well; finding the perfect balance is still under progress, and a lot of optimization of the pins can be done. I have redesigned the character PCB, with smaller pads for easier soldering of the enameled copper wires.

I have made 3 different testing boards, designed as Arduino Uno Shields, for easy testing of the characters. Two of them have a small embedded Oled display for showing the corresponding letter and debugging. I even designed a 3d modeled cover for it ;)