https://devzone.nordicsemi.com/f/nordic-q-a/117561/rtc-appears-to-be-way-out-of-expected-timingOne last issue to crack. This one has been in production for a while and hasn&#39;t caused any issues other than a little annoyance to the customer. By my measurement when RTC is used to count down from 4.00 at 2:55 it will be at 1:55 approx. So basicallyen-USTelligent Community 13Tue, 24 Dec 2024 22:33:24 GMThttps://devzone.nordicsemi.com/thread/516235?ContentTypeID=1Tue, 24 Dec 2024 22:33:24 GMT137ad170-7792-4731-bb38-c0d22fbe4515:057a2bd9-2046-42e4-a9f3-7dd149bf115asnoopy20<p>I have it!<br /><br />After some better timing I discovered it was double. <br /><br />What&#39;s happening is I clear the event at the start of the interrupt, but because the counter is still the same as the compare it immediately refires. Then it dives into the tasks which change the compare value, however the event has already set and it enters the interrupt one more time. Now the compare is different so the clear works.<br /><br />It&#39;s probably related to this errata, though I&#39;m not using PPI. It can also be put down to the sync of different clock domains of course, something I shall have to watch out for in the future.<br /><br />// errata 179 - <a href="https://docs.nordicsemi.com/bundle/errata_nRF52810_Rev3/page/ERR/nRF52810/Rev3/latest/anomaly_810_179.html">docs.nordicsemi.com/.../anomaly_810_179.html</a><br /><br /><br /></p><div style="clear:both;"></div>