Arduino Mega based Accordion midi controller using photointerruptors for bass (left-hand) section mapping and USB midi keyboard for treble (right-hand) section through USB host shield.
Thanks to Dmitry Yegorenkov https://github.com/accordion-mega/AccordionMega/wiki/Accordion-Mega-story I have packed up courage to start my mission to convert an acoustic accordion (Hohner Concerto III in my case) into a digital midi controller. The project took me the whole year 2014 (in my free time) to complete.
I have updated Dmitry's code to the new Arduino IDE and decided to combine with Yuuichi Akagawa's https://github.com/YuuichiAkagawa/USBH_MIDI/blob/master/examples/USB_MIDI_converter/USB_MIDI_converter.ino so that apart from being cost effective, it will have touch sensitivity on the right-hand keyboard and less time-consuming to build. Using an off-the-shelf midi keyboard, first Akai LPK25 and then Samson Graphite M32 to have more keys available, costs approx £50 more but saves you 34 or 41 opto-interrupters and their mapping! The bass section is relatively easier to map since all bass combinations use only 24 pallets.
Bass side pallets with opto-interruptors:
Bass side bellows side showing counterpart opto-interruptor circuits, Arduino-Mega and USB host shield.
First working project using Akai LPK25 controller keyboard:
Final working project using Samson Graphite M32 USB controller keyboard:
First Youtube video showing first prototype - warning! looks very primitive, made several people laugh :)
https://www.youtube.com/watch?v=Fmhv2PbcJrA
Myself playing using the final working project:
https://www.youtube.com/watch?v=ATPYN1C5aeo
Now my project has evolved into https://github.com/JasonBugeja/AccordionMegaBLE