Cut power to nRF52 to switch off system.

[Carlos]

I would like to know the best place to cut the power in switch off sequence.

We have a IO to totally cut power to the IC (own board), I added PIN control to switch off the board inside (SDK 15.3 with SD):

static void shutdown_process(void){}

just before:

ret_code_t ret_code = sd_power_system_off();

I red that sd_power_system_off  does off (NRF_POWER->SYSTEMOFF) and other critical issues to switch off softdevice.

My question is it is safe to cut IC power at this place or it should be done on some other safest way.

The issue is I cannot put switch off pin control after call to sd_power_system_off() because (obviously) the system does not return from this call but cutting power before I am not sure if SD is notified properly that we are going to cut power.

Thks.

C

[Simonr]

Hi Carlos

As long as you don't do this while writing to flash, there should not be a problem cutting the power like this.

Best regards,

Simon

[Carlos]

Hi Simon,

Thank you for your help.

From application side I can be sure everything is safe, my doubt is regarding softdevice, can SD be writting flash within shutdown_process? I guess this is what sd_power_system_off() takes care of (stoping any critical operation).

If this is the case, is there any way to be 100% safe be stoping SD of writing flash?

If all depends on the application then I will close the issue.

BTW, I found some similar questions  on solar beacon, however most links are not reachable like this:

https://infocenter.nordicsemi.com/index.jsp?topic=%252Fcom.nordic.infocenter.nrf52%252Fdita%252Fnrf52%252Fapp_example%252Fsolar_beacon%252Ffirmware.html

If you think this solar beacon example can help me please tell me how to reach it.

Thks again!

[Simonr]

Hi Carlos

You should not cut the power while the SoftDevice, or any other peripherals for that matter, while they are writing to flash. However as long as you wait for the application to finish the flash write. There are no problems with cutting the power like you are describing in your initial ticket.

As for the solar sensor beacon example, it can be found on our NordicPlayground GitHub repository. Please refer to that, as our Infocenter is being reworked at the moment and some links are still not working properly.

Best regards,

Simon