nrf9160 gnss power saving mode

[ncvasil]

Hi all,

I am trying to develop an application that frequently gets location info using gnss and also needs to work with battery.

In the Product Specification v2.2 I found that in continuous mode and power saving enabled - the average current consumption can be around 10 mA:

I decided to try the "nrf/samples/cellular/gnss" example on the nrf9160dk board and measure the current using jumper P22.

I configured the project to use power saving mode like so:

Then build and flashed. While the application was running and the board was trying to get a fix - the measured current was around 38-40 mA, and not the expected 9-10 mA.

I expected the consumption to drop, but it did not. Am I missing something?

I tried the other modes too and they were all the same (around 40 mA as if no power saving mode was selected).

I also checked https://docs.nordicsemi.com/bundle/ncs-latest/page/nrfxlib/nrf_modem/doc/gnss_interface.html#power_saving_mode which summarizes the info from above about gnss power saving mode, but I can not find out why the duty cycling does not kick in. Any advice will be appreciated.

Thanks.

[ncvasil]

Michal said:

So the desired result is for the duty-cycling to timeout after the first fix, right?

Yes

Michal said:

But then, should it always timeout if it cannot get the fix in time (and risk potentially never getting a fix), or maybe every nth try it should still try for longer time?

The second approach sounds like a better trade-off: we accept getting a fix less frequently and have lower power consumption.

If that frequency of getting a fix gets too low (like you said - after nth try we fail) - then it is ok to go back to normal continuous mode with higher power consumption.

That was my understanding while I read this:

https://docs.nordicsemi.com/bundle/ncs-latest/page/nrfxlib/nrf_modem/doc/gnss_interface.html#power_saving_mode

I could be wrong.

It would fit very well in my application. because in case there are no healthy satellites (even on cold start, before first fix) for a certain period of time - I will stop the gnss for a while and not waste any energy while the conditions for a fix are not good.

Hope there is some approach I can use constant (forced) duty-cycling after first fix. Thanks.

Best regards,

Vasil

[Michal]

Thank you for the answers Vasil.

I will have to look more into it and check how exactly it is implemented. Worst case there may be some development needed.

Best regards,

Michal