I use app_timer library, I have a question:
Should I care about RTC1 overflow when using the app_timer library?
The app_timer library has logic for handling overflow, but what is it that you want to achieve or are worry about?
Ok thanks, i was wondering if there is an app_timer API call to find out whether the timer that I have started before is currently running, i found app_timer_cnt_diff_compute() that maybe used for that, but i was not sure if I should handle the overflow...
I don't think there is an API for that. You could use a flag which keeps track of if the timer is started or not. Then clear the flag when the timer stops because of timeout.
app_timer_cnt_diff_compute the difference between two ticks returned by app_timer_cnt_get(). It is related to RTC1 and not to "virtual timers" in app_timer.