SystemOFF mode and BLE advertising

[Dmitry Kr]

Dear Nordic, 

Could you please advice me how to combine system off mode and bluetooth advertisements using Zephyr / nRF Connect SDK? Is there any clear example around? 

The device we're working on shoud be set to ultra low power mode when advertising to save the battery up to 2 years at least. It's imppossbile without system off.

[Simonr]

Hi

When the nRF5x series are in System OFF mode, the CPU is turned off, and thus it's impossible for it to advertise (or do anything for that matter). In system OFF mode it will require an external event to wake up. How often are you planning on advertising? If you're planning on advertising a lot I don't think it will pay off going into system OFF mode at all, as you'll need an external MCU to wake it up, and the wake up procedure is rather power consuming. You might be better off just going into IDLE system ON mode, as that won't draw much more than ~1µA, and it won't be as costly waking up and start advertising.

Best regards,

Simon

[Dmitry Kr]

Dear Simon, 

it's OK to use proposed mode. I thougth we could use just some low-power mode with RTC turned on and MCU awakening by RTC event. 

How we should use it? By PM_STATE_SUSPEND_TO_IDLE or PM_STATE_RUNTIME_IDLE state?

[Dmitry Kr]

Dear Simonr, 

As we checked, for nCS 1.6.1, Zephyr OS automatically changes power mode to the best available. If the device is only advertising, it works fine. 

Let me check all issues related to power modes control, and then we close the issue.