I received the boards 1 week ago and started programming the firmware today. For the 7 segment version of the meter I used a standard 0.1" header for the ICSP but since the OLED version is smaller, i used 0.05" SMD pads instead.

Originally I wanted to use Pogo Pins and build a small programming adapter that you could attach to the back that presses the spring loaded pins on to the pads. But since it took a bit longer for the boards to arrive I now simply soldered the wires directly to the board: -> cheap and hacky but works like a charm :)

the unpopulated boards with the programming header on the back

soldered wires to the programming header

As I said it works quite well but after some programming I lost the reset pad because I did not tack the cables down. This was not a problem since I could still attach the reset line to the pullup resistor but as I said this is a hacky solution.

In the end I also lost part of the the 5V pad. Again, I can reattach the cable o another component so the board still works fine.