I soldered the PCB and assembled all the parts. I still need to cut the screws to the right length, but apart from that the hardware is finished. The PCB is functional, but there are some things I would change next time. For instance:

• label the individual pins of the connectors
• label the "reset" and "flash" buttons
• use an 0805 diode package instead of an 0805 resistor package for diodes (on the PCB is no mark how the diode should be installed)

I will make an example code, which shows how to use the buttons and control the LEDs. The code should be on github in a week or so.

PS: If someone near to Austria wants a PCB, drop me a line, I don't need all of them.