I just created the app_led.c and app_led.h files and define a function under the new folder, then called the function in app_main.c. This will cause a compilation error.
BUT, if I define the same function under the existing folder (app_end_device_node.c), then called the function in app_main.c. This will be no error.
Is this because the .c.h file I created requires additional system configuration?
Please give me some accurate advice, I have spent too much time to solve this problem, thank you very much.