To add to my own question, I think this may be an issue with the compiler finding a duplicate header file called “common.h” in the framework folders. If I rename the project “common.h” to something else (e.g. “myHeader.h”) and update all references in src files, the code compiles fine. But I’m not sure why it is picking up the wrong header - should it not pick up headers from project “include” folder before any framework ones?
I thought perhaps it was related to this post: PIO library doesn't see header files in project's include folder but it makes no difference if I add “build_flags = -I include” to the platformio.ini.
My project folder structure looks like this:
I’m sure I’m missing something really obvious - any input gratefully received!