Edit August 15th, 2018: Parts ordered.
All parts are ordered and are expected to arrive in around two weeks from china. I hope to finish my board this weekend to send it to the fab as well, so I can start my first assembly.
The final design will look quite different from the mock-up...
The following pics show the test-placement of the components on a 25mm square:
Always funny to see the how big "dumb" passives can be compared to e.g. the Atmega328 in its 5x5mm case. Caps are 0805, LED is PLCC4... As I will need to place a few other passives I guess I need to switch to 0603 or 0402 for this project. Soldering only one 0603 or two 0402 LEDs would save additional space as well.
Of course placement is just to get a broad overview of how much space I've got to play with, not final placement.
The coin cell holder will take much of the PCB bottom side. Battery needs to be easily accessed, so I can't place components where the battery is slided in. Top 2 pics are CR1225, bottom pics are CR1632. As I#ll go with the CR16xx cells, bottom left seems most space-saving.
That's it for today. Weekend is here, need to have a few beers :)