Today the LEDs I ordered finally arrived. A couple of days ago I stumbled upon a wiring technique called “charlieplexing”, which is explained quite thorough in this article. If my calculations are correct I’m going to need 12 pins on the Arduino to control the LEDs and another one for the DCF module, so I’ll be good with the regular 14 pins.
So, next I’ll start wiring up some LEDs for testing. As long as I don’t have the DCF module some dummy clock function will have to to.