System_off example has increased power consumption when using k_sleep iso system_off

[Ypenburg]

I run the system_off example without the system actually going off, by removing all the calls to start the system_off worker. Instead of going to off, I let the system enter sleep mode (k_sleep()).

I enabled wake up on nfc.

After a reset, the system enters sleep (4-5uA sleep current). After waking the system by nfc, the sleep current sometimes becomes 200uA, sometimes stays at 4uA. See picture below.

It seems to be related to the state of the nfc peripheral as this is the only peripheral used.

Any idea how to prevent the system going to sleep with a 200uA sleep current?

[Simonr]

Hi

Where does the application go to sleep exactly? Since you've figured out it is the NFC register values doing this it might be that the application goes into a sleep mode before the nfc_t4t_done() function is done uninitializing the NFC peripheral so it is still running when in sleep. You could try adding a wait/check to make sure that the nfc_t4t_done() is completed before the k_sleep is called.

Best regards,

Simon

[Ypenburg]

What I did to verify it is not a problem created by me, is rework the system off example

The system_off example creates a worker that puts the device in system off mode after a timeout.

Remove the worker calls, so that the device does not calls the system_off function and let the main loop sleep forever.

I expect to see a very low current, but sometimes see the 200uA when woken up by the nfc peripheral (or otherwise, did not test that)