Designing and building the display:
About the Bluetooth data transfer:
Two PCBs (left half 8 x 10, right half 8 x 10) designed in KiCad (see files) and Milled into PCB material using my CNC milling machine. Standard green LEDs. The distance between two LEDs is 9mm.
Multiplex-configuration: All (+) per row connected and all (-) per column. The (-) are driven by Darlington-drivers, the (+) by PNP transistors.
PCB (see files) created in KiCad and milled.
Rows: Individual PNP transistors, one data-line to the arduino per row.
Columns: Two daisy-chained SerToPar Shift-registers control two darlington arrays.
Cheap BT speaker, the class-D amp got disconnected from the DAC and the signal is fed into an analog port of the arduino.
Clock: PCB from a Cheap wall clock, the coil-signal drives a transistor which pulls down a digital port of the arduino every two seconds.