multiple definition of ...

[RaphyStark]

Hello,

I'm working with https://github.com/elegooofficial/ELEGOO-TumbllerV1.1-Self-Balancing-Car-Tutorial, which is the software of the Tumbler Self Balancing Car (a robot for fun but also education seeing that the source code is open source).
I'm struggling with the "include "PinChangeInt.h".
I want to be able to call this header file in each .cpp I need it.
Previously, it was called only once in the main.cpp, but it force the user to declare and define his variables and functions directly in the header files of his project.
If I want to declare my variables and functions in hpp files, and define them in cpp files, I'll have to include PinChangeInt in every cpp file who need it. This cause "multiple definition of (things in PinChangeInt.h)".

What can you advise me ??

Thank you !
Raphaël.