"Sleepmodes" on nRF-9160 during LTE PSM?

[ExAg]

Hi

We are developing an IoT device that should send its telemetry to an Azure IoT hub.
therefore we have choosen the nRF-9160 DK with the azure_iot_hub sample, which works well for our tests and POC so far.

What is essential for our project is the fact that we are battery powered and should be as "low power" as possible.
Currently, we have activated PSM for the LTE connection and are planning to use eDRX as well.
But we think that all this makes only sense, if it's possible to set not only the modem but also the nRF-9160 "micro controller part" into a powersave or sleep mode.
We found some hints in the devzone; but all these entries were very outdated and did not work anymore. For example CONFIG_POWER_OPTIMIZATION_ENABLE=y seems to no longer exist.
As well as the refered "Asset Tracker" sample, that is no longer part of the samples folder.

So the question is, if there is some documentation on how to use powersave or sleepmodes on the nRF-9160 in combination with an LTE (NB or M) connection?
Our target is to wakeup from timer, than send the telemetry, wait until modem is back in PSM and than "go to sleep" until next timer expiry (and so on).


Regards
Michael

[Charlie]

Hi Michael,

We have a webinar introducing How to power optimize with the latest features in the nRF9160 SiP - Nordic Semiconductor.

the nRF-9160 "micro controller part" into a powersave or sleep mode.

The application core will enter sleeping mode automatically when the application is idle, Zephyr RTOS help you manage this. 

As well as the refered "Asset Tracker" sample, that is no longer part of the samples folder.

You can refer to nRF9160: Asset Tracker v2 — nRF Connect SDK 2.2.0 documentation (nordicsemi.com), which has been redesigned from Asset Tracker with Ultra-low power optimization in mind.

if there is some documentation on how to use powersave or sleepmodes on the nRF-9160 in combination with an LTE (NB or M) connection?

Here are some other references about low power consumption optimization.

(+) nrf9160 LTE Serial Modem App UART power management - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

(+) Optimal way of putting nRF9160 into low power mode without shutting down the power - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

Our target is to wakeup from timer, than send the telemetry, wait until modem is back in PSM and than "go to sleep" until next timer expiry (and so on).

The device will "go to sleep" when it enters PSM mode if it has no other task to do and become idle. The following UDP sample shows the floor current nRF9160 can achieve at PSM mode. When you have a timer running in the background, it will consume more current.

charlieshao5189/udp_sample_with_buttons_control at udp_rel14_rai (github.com)

Best regards,

Charlie

[ExAg]

Hi Charlie

Thank you very much for your answer! I will have a look to all the documents and information you mentioned. I will come back to you if I have any further questions.

At the moment, I measure about 600uA during PSM on the nRF9160-DK, what is pretty high I think.
My application is based on the Azure_iot_hub sample from the SDK, but uses PSM and sends telemetry every 55 seconds in stead of every 20 seconds.
And probably I write it wrong: it's not directly a timer but the k_work_reschedule_for_queue() function that we are using for the telemetry interval. But I think it needs a timer too in background?

 

Regards
Michael

[Charlie]

Hi Michael,

ExAg said:

At the moment, I measure about 600uA during PSM on the nRF9160-DK, what is pretty high I think.

Have you turned off your log and UART port?

You can refer to the configuration on nrf\applications\asset_tracker_v2\overlay-low-power.conf.

ExAg said:

But I think it needs a timer too in background?

Yes, it is.

The protocols and LTE connection method will also affect power consumption. Here are two more references explained on a higher level for a cellular IoT application built from scratch.

nWP044 - Best practices for cellular IoT development

2022.03-GSMA-Energy-Efficiency-for-Mobile-IoT-1.pdf

Best regards,

Charlie

[ExAg]

Charlie said:

Have you turned off your log and UART port?

ohh - of course not...

With the settings from "overlay-low-power.conf" I now achieve a minimum of 30uA in the PSM.That's really good!
But I still need to understand exactly the influences of all these settings.

Thank you very much for your very quick help!

Best regards
Michael