Arduino-based Darkroom "F/stop" Enlarger Timer

Here is a darkroom enlarger timer I built. The open-source code came from an Italian photography web site. I made a few fixes and enhancements to the code. The f/stop functions allow adjusting print exposure in f/stop units rather than in time. The code and a discussion are on the Photrio web site: https://www.photrio.com/forum/threads/homebrew-f-stop-timer.158118/ The original design discussion may be found here: https://www.analogica.it/upgrade-timer-con-keypad-t6797.html and https://github.com/ciromattia/timerino