Simple way to move to power saving mode - NCS3.02/nRf52840

[eyalasko]

Hi, 

I'm running an app on nRF52840 (NCS3.02) based on the BT shell example.

I did the following modifications:

- shell runs on USB-CDC instead of UART

- using NRFX drivers for I2C & UART (not DT)

- UART0 disabled (app.overlay)

- Everything is asynchronous - threads are blocked on semaphores/queues, triggered by NRF GPIO interrupt (NOT DT), NRFX UART initialized only after GPIO interrupt

I would expect that the app stays 99.99% of the time in the idle task. 

Still I get 7-8mA consumption when everything is idle (idle task?)

Tried the following

CONFIG_PM=y
CONFIG_PM_DEVICE=y
CONFIG_PM_DEVICE_RUNTIME=y         # Let drivers autosuspend when unused
CONFIG_PM_POLICY_DEFAULT=y         # Kernel chooses best sleep in idle
CONFIG_TICKLESS_KERNEL=y           # Idle time extends, fewer RTC ticks

but it keeps drawing 7mA...

What is the easiest way to cut the power down?

For a start,  I don't need an aggressive power optimization, just to take this constant current draw down ...

Thanks

I 

[Simonr]

Hi

For starters, can you confirm you've followed the https://docs.nordicsemi.com/bundle/ncs-3.0.2/page/nrf/test_and_optimize/optimizing/power_general.html guide in our documentation pages?

Additionally, as of NCS 3.1.0 we added a config for async device runtime power management with CONFIG_PM_DEVICE_RUNTIME_ASYNC which might be useful in your use case.

Best regards,

Simon

[eyalasko]

Hello Simonr, thanks for your prompt reply

I followed your advice and managed to reduce consumption to ~2mA.
Using PPK2 I see a current spike every ~60msec. Nothing I can think of on the app side.
Can it be some idle/shell/logging thread waking up periodically?

[eyalasko]

one more thing - 

It seems as there's a missing dependency and CONFIG_PM is not activated (see squiggly line and pop up message)...