Thanks to everybody for your help and suggestions.
I will consider all of them and review the project.
I have a Wemos D1 motor shield
but it doesn't work.
When I try the examples in the library, I always have the same Error: WDT reset.
Same problem with and empty program, with just the #include "WEMOS_Motor.h"
So I wrote this program (extracting info from the lib):
Using IDE 1.6.6
Compile and run OK, but motors doesn't run.
Any idea and suggestions?