nrf52832 poweroff mode question

[Ivan]

Hello.

I 've analyzed a couple of topics here regarding to poweroff.
But still want to clarify something.

In my project I need to keep MCU in lowest possible power mode, but with ability to wake it up after some predefined amount of time,
to switch on RF on some short period and than power down again.
I was able to set RTC proper way to count this intervals. But the problem is, that in lowest poweroff mode RTC is off.
Mode with idle power down with working RTC still uses about 600uA which is too much.

So my question is, poweroff mode can has wake up only on GPIO and no low-power timer can be used to count and wake-up?
Same is for watchdog, can't I use it in poweroff to reset MCU?

Kind regards.
Ivan.

[Simonr]

Hi Ivan

Depending on whether you need RAM retention you should be able to run the RTC and wake up from the RTC at ~2µA, so something else is definitely running in your application. Please do as Ameer Usman is suggesting and make sure logging is turned off when you measure the current consumption. Can you also tell me what exactly your application is doing while it's awake and what SDK you're using? I think there might be a peripheral that isn't disabled properly before going to sleep.

As for timers to wake up the chip in system OFF mode, you would have to have a separate MCU with a timer and is powered separately in order to wake up the device from system OFF at timed intervals.

Best regards,

Simon

[Ivan]

But how to set RTC to wake up on some counter value?
I need to count in ms during pre-set amount of time and after reaching value - wakeup chip for some another amount of time. During this wakeup I swich on the radio (ESB mode). Than I disable it and go for new sleep with counting RTC.

Logs are disabled in sdk_config, log_init is not called.

Main app checking RTC counter value and switch on/off radio.

[Simonr]

Please check out this case, which has a snippet of code and an explanation on how to set the RTC to run when going to sleep. Also, check out the RTC example in our SDK to see how you initialize the RTC and what files/headers are necessary.

Best regards,

Simon