Suddenly app_timer events trigger instantly

RE: Suddenly app_timer events trigger instantly

Chris — Mon, 28 Sep 2015 22:47:59 GMT

I think I 'fixed' this by creating a dummy timer as in this post here: devzone.nordicsemi.com/.../

So far no more glitches (crosses fingers...).

In that post, Håkon Alseth, alludes that this should not be needed post SDK6.1, but I am on 8.0.0.

RE: Suddenly app_timer events trigger instantly

RK — Fri, 25 Sep 2015 07:54:04 GMT

Ah - yes does help to know what you've tried, if that didn't work for you then it looks like a different bug. I meant that in this case you should, instead of the delay, set the counter to that value ( pre_counter_val - 1 ) & 0xffffff, I guess it would be something like

rtc1_compare0_set( ( pre_counter_val - 1 ) & 0xffffff );

it goes in the same if() block where timer_timeouts_check_sched() is called, before or after, shouln't matter.

The idea behind the nrf_delay( 100 ) fix is to ensure that the counter event has definitely fired before you return, which means it won't fire during the RTC1 interrupt handler. The idea behind the other fix is to set the counter to a value way in the future, so if it hasn't fired already, it won't fire until long after the interrupt handler has finished. Having the RTC1 compare occur during the RTC1 interrupt is the race condition.

RE: Suddenly app_timer events trigger instantly

Chris — Fri, 25 Sep 2015 07:26:32 GMT

I should have mentioned that I already implemented the "nrf_delay_us(100);" 'fix' from that thread, but I thought it was something else since it sounded like one misfire, whereas mine is misfiring continuously. I would like to try your solution, but I don't completely understand how to implement it. Do you mean to put "pre_counter_val = (pre_counter_val-1) & 0xffffff;" instead of "nrf_delay_us(100);"?

RE: Suddenly app_timer events trigger instantly

RK — Fri, 25 Sep 2015 06:48:56 GMT

Read all the comments at the end of devzone.nordicsemi.com/.../ that question which talks about a race condition which causes events to trigger instantly and discusses two potential fixes.