Feeling a little stupid here, but none of the Pin names mentioned in the P1 datasheet are declared? https://docs.particle.io/datasheets/p1-datasheet/#complete-p1-module-pin-listing
error: 'MICRO_GPIO_5' was not declared in this scope
I guess that’s no biggie because all I need to do is to include … (please insert in the correct class name here)
@jenschr, these are the P1 module pin names but not the actual mapped pin names. The mapped pins and their names are show above in the Pinout Diagram. 
Duhh… Yeah.
I finally got it. It’s such a mess when you don’t print the actual Pin names on the PCB
I made the PCB 2-3 months ago and finally had time to test and play with it now. The good news - it all works as expected!