The Haji keyboard uses 8-bit shift registers, rather than the typical keyboard matrix cirucit. An advantage in using shift registers is that you can add any amount of keys, instead of being limited by the amount of I/O pins. It uses an STM32F1 chip to communicate to a computer using its native USB interface. I sourced components, designed and fabricated the pcb, soldered, built, and programmed a fully working prototype of a small macropad from scratch.
##PARTS NOTES: HOTSWAPPABLE SWITCHES
ICS: STM32F1 74HC165D,653
MODULES: UNIFIED C3