Undefined symbol error when adding Simple_timer to uart example in Keil

[claudea159]

When I add a PWM or simple timer to a uart example I get the error in Keil.

Simple timer: I added app_simple_timer.c to the library, I added the #include "app_simple_timer.h" and I added the path to the Project Options.

My code is very simple:

// Initialize timer
   uint32_t err_code1 = app_simple_timer_init();
    APP_ERROR_CHECK(err_code1);
	// start timer for PWM 
   err_code = app_simple_timer_start(APP_SIMPLE_TIMER_MODE_REPEATED, PWM_timer_handler, 50000, NULL);
    APP_ERROR_CHECK(err_code);

I have the same problem with the PWM_Library.

Thanks

[claudea159]

I compared the sdk_config (with the wizard) between the example and my project. The app_simple_timer is in the example and checked but not in my project sdk_config.  I believe, I am not adding the library correctly.