Disable cryptocell hardware to save power

[jonas.woerner]

Hi,

currently I am trying to figure out how to disable the cryptocell hardware after enabling it, because if I enable it and then enter systemOFF, the system still draws about 35uA.

I enable it with:

NRF_CRYPTOCELL->ENABLE = 1;

then the system draws about 800uA of power.

then I do

NRF_CRYPTOCELL->ENABLE = 0;

and enter systemOFF, but I still draw some current.

If I dont enable it prior, my current goes down below 1uA.

so How do I completly disable the cryptocell processor?

thanks,

Jonas

[Simonr]

Hi Jonas

Please check out the cc310_backend_uninit() function in the cc310_backend_init.c file. This shows how to properly shut down the Cryptocell processor.

Best regards,

Simon

[jonas.woerner]

thanks,

I looked into it, but from my understanding it just de-initializes a library and then does the same thing as I do, nothing special... So in theory my approach should work?

[jonas.woerner]

upon further testing, I think it DOES work, but something else is drawing power. when I disable the cc310, the current drops significantly, but stays at about 38uA, even in systemOFF.

the same behaviour can be seen if I used the radio and then enter systemOFF, there is also a power draw of about 38uA...

I think these two issues are the same maybe?

[jonas.woerner]

I did some more testing and came to this conclusion:

https://devzone.nordicsemi.com/f/nordic-q-a/46079/nrf52840-too-high-systemoff-current

any help is appreciated.

[Simonr]

Hi Jonas

Seeing as this is a more general issue than first anticipated, I will continue this over on the new post you created, and will be closing this one to avoid confusion.

Best regards,

Simon