There are plenty of drones (and other gadgets) you can buy online that use proprietary control protocols. Of course, reverse-engineering one of these protocols is a hacker community classic. Today, ...
Use the 6-pin ICSP header on Arduino Nano (best reliability): ICSP Header Location on Nano: ┌─────────────────────────────┐ │ ┌──┬──┐ │ │ │ │ │ ← = Pin 1 ...