https://devzone.nordicsemi.com/f/nordic-q-a/17986/nrf51-sleeping-a-certain-timeHello, my program should do the following: Collect sensor data Initialize SD and start advertising After a timeout or after a successful data connection it should sleep for half an hour. When waking up, it should start from the beginningen-USTelligent Community 13Mon, 28 Nov 2016 10:12:22 GMThttps://devzone.nordicsemi.com/thread/69349?ContentTypeID=1Mon, 28 Nov 2016 10:12:22 GMT137ad170-7792-4731-bb38-c0d22fbe4515:112f2fec-107d-4449-a408-5dddd0570c20J&#248;rgen Holmefjord<p>Hi,</p> <p>You should use a timer to set a periodical wakeup from sleep to collect and send sensor data. I would recommend that you take a look at the <a href="https://devzone.nordicsemi.com/tutorials/19/">Application Timer Tutorial</a>. The application timer module use <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/rtc.html?cp=2_2_0_24#concept_rvn_vkj_sr">RTC</a> instead of timers, which is more power efficient. You can also take a look at this <a href="https://github.com/NordicSemiconductor/nRF52-ADC-examples/tree/master/saadc_low_power">nRF52 ADC example</a>, where a RTC is setup for periodical capture of battery voltage.</p> <p>Notice that you can only use <em><a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/power.html?cp=2_2_0_17_2#unique_752213511">system on sleep mode</a></em>, when using timers. <em><a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/power.html?cp=2_2_0_17_1#unique_863354678">System off sleep mode</a></em> will disable all clock sources.</p> <p>An alterantive, which might be more power efficient, is to add an external ULP timer. You can then put the nRF device in <em>system off</em> mode, <a href="http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/power.html?cp=2_2_0_17_9_0#unique_1502638242">lowering the current consumption</a> compared to <em>system on</em> mode, and configure the device to wake on GPIO/GPIOTE. You can find some exampes of the different sleep modes <a href="https://github.com/NordicSemiconductor/nrf51-powerdown-examples">on GitHub</a>.</p> <p>Best regards,</p> <p>Jørgen</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/69348?ContentTypeID=1Sat, 26 Nov 2016 21:56:11 GMT137ad170-7792-4731-bb38-c0d22fbe4515:548aa0f7-59a9-47c5-9ad1-5e577c827458Roger Clark<p>Why not just use a timer ?</p><div style="clear:both;"></div>