Minimum softdevice initialization functions

[bloobird0]

Hello,

In my application, I need to activate BLE during startup only if some conditions are met otherwise I put the nRF52 in SystemOff mode. BLE should not be activated during the conditions check in order to keep the power consumption as low as possible.

Because the sd_power_system_off() is used to go in SystemOff mode, the softdevice must be initialized and running first.

What is the softdevice minimum initializations steps that allows sd_power_system_off() to be called without BLE being activated and using more current?

is SOFTDEVICE_HANDLER_INIT() sufficient or should also softdevice_enable() function be called?

The application is a BLE peripheral. Advertising is only started when all required conditions are met. Do I gain power consumption with the above described sequence?

Is it possible to put the nRF52 in SystemOFF mode without using SoftDevice although it is available in Flash?

[Jørgen Holmefjord]

Hi,

As long as the softdevice is not enabled, you can use the registers directly to put the device into System off mode:

NRF_POWER->SYSTEMOFF = 1;

You can find some power-down examples on our GitHub page.

If the softdevice has been initialized, you will have to use the sd_power_system_off() function.

Best regards,

Jørgen

[bloobird0]

Thanks, seems OK. Nevertheless I find that the app_timer does not fire anymore until the softdevice is initialized. Is App_timer softdevice-dependent?

[bloobird0]

Edit: it looks like that app_timer uses the RTC. I don't have any 32kHz crystal on my board so I use the internal LFRC clock when configuring the softdevice. I may explain why my app_timer does not fire before initializing the softdevice.

[Jørgen Holmefjord]

You can start the LF RC without initializing the softdevice. This is described in this post.