https://devzone.nordicsemi.com/f/nordic-q-a/11684/problem-by-waking-up-from-power-offDuring Power Off mode the nRF52 GPIOs stay retained. But by waking up on a external Pin we can see another Pin toggles for approx. 600ns. It seems this happens during the reset. The Pin which toggles is configured as output. The Pin toggles before theen-USTelligent Community 13Wed, 03 Feb 2016 08:38:47 GMThttps://devzone.nordicsemi.com/thread/44160?ContentTypeID=1Wed, 03 Feb 2016 08:38:47 GMT137ad170-7792-4731-bb38-c0d22fbe4515:39a6d1a1-c0af-4005-ad65-e73b3f17b25cKenneth<p>Hi, The likely problem is that all peripherals except the GPIO is reset after system OFF. This is what happens:</p> <p>When you go to system off the pad will latch and retain configuration it get from the peripheral (which wins). This configuration will be kept as long as it’s in system off. When the system wakeup the peripheral will power up, and pad will also wakeup. Now, since the peripheral is reset, and no longer request the pad, the pin configuration will decide how the pad behave and the configuration will change.</p> <p>So our recommendation is to configure the GPIO pin configuration and level to the same configuration as you want the peripheral to use the pad before going to system off. That way when the system wakeup, it will will fall back to the GPIO configuration and level. So make sure to set PIN_CNF[] and OUTSET/OUTCLR to the same level as the peripheral using the pin before going to system off, for instance by using the api in nrf_gpio.h.</p><div style="clear:both;"></div>