I've wired everything up with my Atmega328P on a breadboard, including:

• 9V power supply through regulator
• connection to LED panel
• shutter release trigger to 3.5mm jack
• rotary encoder

The encoder doesn't seem to work reliably, but I'm pretty sure it's a software problem. It's configured with INPUT_PULLUP in the code, and is connected to ground in the encoder itself, so it's probably not a voltage problem.

One thing missing so far is an interface to analog input. I may just wire that directly later. Just want to keep it simple for now.

I've put in an order to DirtyPCBs, but I named the files wrong in the ZIP. We'll see if that causes a problem.