Timer under 5ms

[dblasco]

Hello,

I have added a timer to my code, which I need to be of 1ms. The handler of the timer is correctly called when the timer is 5ms or above. However, if I change it to less than 5ms the handler is never called.

Here is some of the code I used (using softdevice):

[...]

static app_timer_id_t timtecil;
uint32_t counter=0;

void timtecil_handler(void * p_context)
{
	UNUSED_PARAMETER(p_context);
	counter++;
}

[...]

int main(void)
{
[...]
    
err_code=app_timer_create(&timtecil,APP_TIMER_MODE_REPEATED,timtecil_handler);
err_code=app_timer_start(timtecil,APP_TIMER_MULTIPLICADOR*0.001,NULL);

[...]

    for (;;)
    {
        app_sched_execute();
        power_manage(); 
				
    }

}

The constant APP_TIMER_MULTIPLICADOR (= 1024) is used to match the necessary number of ticks so I write only the period in seconds. I use APP_TIMER_PRESCALER = 31 (so the shortest timer possible is 0,000976563 seconds).

Any explanation?

Thank you very much.

[Krzysztof Chruscinski]

You are hitting minimum acceptable timeout_ticks value.

• @param[in] timeout_ticks Number of ticks (of RTC1, including prescaling) to time-out event *
  (minimum 5 ticks).

app_timer_start should return error code in that case.

If you want to have 1ms tick you need to decrease APP_TIMER_PRESCALER so that 1ms is more than 5 ticks.

[dblasco]

You both were right! I had to change APP_TIMER_PRESCALER to 3 so 1ms were at least 5 ticks. Now it is working.

Thank you very much!