https://devzone.nordicsemi.com/f/nordic-q-a/15809/app-timer-accuracyHello, I&#39;ve got a problem with an app_timer starting from the BLE_UART example, I&#39;ve set #define APP_TIMER_PRESCALER 4 #define CLOCK_CONFIG_LF_SRC NRF_CLOCK_LF_SRC_Xtal and create a timer with app_timer_create(&amp;m_alert_timer_id, APP_TIMER_MODE_REPEATEDen-USTelligent Community 13Thu, 18 Aug 2016 15:23:18 GMThttps://devzone.nordicsemi.com/thread/60349?ContentTypeID=1Thu, 18 Aug 2016 15:23:18 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b92cb79e-fdff-4a6e-b892-ccdc061dcbd6cedric<p>it&#39;s clealy that, I was confused by the nrf_drv_rtc.c (too much work around the rtc use) which is not used by the app_timer.c since the last as it&#39;s own writes in the rtc peripheral... Thanks John.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/60348?ContentTypeID=1Wed, 17 Aug 2016 20:07:07 GMT137ad170-7792-4731-bb38-c0d22fbe4515:037eec44-a8de-45c9-a513-6ecb98d4f326John<p>According to the nRF52 documents, the calculation for frequency with regards to the prescaler is:</p> <p>fRTC [kHz] = 32.768 / (PRESCALER + 1 )</p> <p>So to use 8192 the prescaler should be set to 3. I ran into this once on the nRF51 and it took a while for it to sink in that the prescaler starts at 0, not 1.</p><div style="clear:both;"></div>