Cessna 172 Radio Stack V3.1
1. Arduino Mega 2560 directly attachable to the back of the PCB (only one Arduino Mega 2560 Pro (small arduino) needed, no need for Arduino shield).
2. Added input shift registers (74HC165) for the push buttons, the number of Arduino pins reduced a lot.
3. Added output shift registers (74HC595), all LEDs are now handled through 74HC959 shift registers, supplied externally with +5V, no current drawn from Arduino
4. Replaced the Transponder rotary switch with a smaller one.
https://flyingforfun.weebly.com/cessna-172-cockpit.html/#RadioPCB