Sleep modes (System ON) example for nRF52833 with nRF Connect SDK 2.3.0

Question

Dear Support Team, 
 
 I recently started evaluating a nRF52833 DK board with the nRF Connect SDK 2.3.0. Could you please point me to a working example demonstrating how to configure and use the different sleep modes? I'm interested in the implementation of the various System ON modes described in the data sheet:

Thank you very much in advance and all the best, 
 Viktor

Einar Thorsrud · Accepted Answer

Hi Victor, 
 I do not have any examples on ON_RAMOFF_EVENT, other than referring to how you can configure the RAM retention at register level as done in the nRF5x System Off demo. I think that has very few practical applications though, and I do not recall seeing system ON sleep with no ram retention ever used. If you have no RAM retention, all initialization will have to happen again when you wake up from sleep, which will will require significant amount of CPU time and resources. So this will likely increase your products average power consumption, which in the end is what matters for battery life. 
 Regarding ON_RAMON_EVENT this is also mostly of theoretical use, as it includes the CPU configured to wake up on any event, but no wake-up sources (like RTC, LPCOMP, GPIO,..) actually configured. 
 The most relevant sleep mode is systen on sleep mode with RTC, with RAM retention, which is what is used for I_ON_RAMON_RTC (2.6 uA). With this, the RTC keeps running and is used as wakeup source. Also, the full RAM is retained, so you do not need to re-initialize anything. For GPIO, you can use port event instead of in event, and that will give you a lower sleep current consumption, as you see in the table (I_RAMON_GPIOTE_PORT). Combining GPIO port event and RTC and full RAM retention, you should expect to see an idle current consumption of slightly above 3 uA. 
 If you find you don't use the full RAM, you can change the linker memory configuration so that the upper part is not used, and disable that in the power register (see how that is done in zephyr/samples/boards/nrf/system_off/src/retained.c). As you see in the table, the difference between full ram retention and no RAM retention is 0.7 uA, so depending on how much RAM you can live without, this will not make a huge saving, though. 
 Einar

Sleep modes (System ON) example for nRF52833 with nRF Connect SDK 2.3.0

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