Timer handler not called

Question

I know this was asked before, but none of the posts address my problem. There is a similar thread , but the issue on that one was that the softdevice was not being used. I'm using S210 softdevice and trying to make a current efficient delay using a timer, but my handler is never called: 
 // do nothing

static void delay(void * p_context)

{

// do nothing

}


 app_timer_id_t module_init(void)

{

	
 // Initialize and start a single shot timer, which is used as a delay

 APP_TIMER_INIT(RTC_PRESCALER, 1u, 1u, false);
 app_timer_id_t timer_id;
 uint32_t err_code = app_timer_create(&timer_id, APP_TIMER_MODE_SINGLE_SHOT, delay);
 APP_ERROR_CHECK(err_code);

	
	return (timer_id);
}

	

app_timer_id_t timer_id;
	
{
.
.
.

 timer_id = module_init(); 

 uint32_t err_code = app_timer_start(timer_id, 50u, NULL); 

 app_timer_stop(timer_id);
	
.
.
.
.
}

RK · Accepted Answer

What do you expect that code to do? 
 You start a timer, then you instantly stop it again. Or have you left out some code from the real project? 
 Did you think that app_timer_start() is a blocking call which only returns when the timer fires, because it's not, it instantly returns and continues running the code and the timer firing happens in an interrupt handler entirely asynchronously, calling your handler at that point. 
 If you are trying to delay you want something more like this (untested) 
 static void *delay( void *p_context )
{
 *((bool*)p_context)=true;
}

{
 ...

 bool has_fired = false;
 uint32_t err_code = app_timer_start( timer_id, (void*)(&has_fired);
 while( !has_fired)
 __wfe();
 ...
}
 
 So the delay() routine sets the flag that the timer has finished and any interrupt or event in the system (including the timer IRQ) will wake up the __wfe() call to check it. After the timer successfully fires you'll drop out of the while loop and continue. 
 PS As a matter of good practice I suggest wrapping any call which can produce an error in APP_ERROR_CHECK() or similar, at least in a debug build. It's saved me hours of debugging time because it instantly dumps you in the error handler and you can figure out what call you made failed, and why.