Power Management and SystemON Idle

RE: Power Management and SystemON Idle

Hung Bui — Thu, 05 Mar 2020 13:57:52 GMT

When you use NRF_LOG_DEFERRED the log printing will not be blocking function (CPU have to stay at log module when printing out log). Instead it will be executed in the background and when it's finished there will be an interrupt. This lead to the issue you saw :)

RE: Power Management and SystemON Idle

Jose Forno — Thu, 05 Mar 2020 13:20:26 GMT

Hi Hung,

Thanks very much. I disabled the NRF_LOG_DEFERRED in the sdk_config and it worked.

A last question, what does the NRF_LOG_DEFERRED do?

Best regards

José Forno

RE: Power Management and SystemON Idle

Hung Bui — Thu, 05 Mar 2020 09:36:59 GMT

Hi Jose,

A quick test here showed that it was the UART logging module that caused some interrupt and woke the CPU up. This in turn will cause a UART log printing, and then will trigger another interrupt (most likely TX done) and so on.

If you change UART logging to RTT logging (which doesn't have an interrupt) or remove NRF_LOG_DEFERRED in sdk_config.h it would work as it should.

RE: Power Management and SystemON Idle

Jose Forno — Wed, 04 Mar 2020 15:49:07 GMT

Hi Hung,

Thanks for your answer.

I'm not using softdevice, and only one app timer is used.

I use the "pwm_mgmt" example of the SDK v16.0.0 as a starting point. I only add one app timer and commented the buttons assignations code , because my board only have one button. The application doesn't init the leds in the BSP, only the buttons.

As far as I know the BSP library use the app timer, but I tested the code removing all the bsp code and the problems persist. Also, with the "nrf_pwr_mgmt_run" commented and the "SEV, WFE" uncommented the problem disappear, even with BSP library running (without pressing the button off course).

The full code (it's only one file):

devzone.nordicsemi.com/.../64816.main.c

And the sdk_config.h:

devzone.nordicsemi.com/.../13646.sdk_5F00_config.h

Best regards

José Forno

RE: Power Management and SystemON Idle

Hung Bui — Wed, 04 Mar 2020 14:08:11 GMT

Hi Jose,

One easy way to track the timing of the CPU sleep mode is to toggle a GPIO in the main loop before and after the "enter sleep mode" command. Doing that you can monitor the active time before entering to sleep. You can also use the power profiler kit to measure the current to investigate.

Do you have anything else running in your code ? Any other app timer, there is a chance that other modules also have app timer ? was the softdevice active ?
Please post your full code.