This concludes the hardware prototyping part. I'm genuinely surprised that the entire circuit works without any further modification, and that it could actually have been my final PCB.

All of the target functionalities were implemented and have been proven to work in previous logs :

• Have a controller that fits on the mounting holes of the ANNAX display
• Interface with the display using built-in dual IDC 40-pin connectors without modifications
• Flip and unflip dots at a pretty fast rate
• Illuminate the LED of the flipped dots
• Chain several displays and controllers together to expand fun area.

Minor modifications on the PCB would be to change the screw-terminal for the +24V input/output into a wire-to-board connector (maybe Molex ?), as it's currently quite a pain to connect/disconnect the cable when needed. And that's it ! The rest works.

A lot remains to be done though :

• Software : I need to write some kind of library for basic display functions (dot, line, rectangle, circle, text, icons, etc.) which would make my life easier when coding the final usage I want to do with the display, and make the webpage to control the display from any phone/tablet, making the whole thing IoT.

• Hardware : And in parallel, I need to revert to using the ESP32, and design a board for the ESP, some buttons and encoder, the level shifting required, and voltage/current regulation to complete the project

So it's far from being finished, but great steady progress were made over the past two months and I hope to keep it going this way.