Softdevice - Wake up from deep sleep after a predefined time is not possible, What is an alternate solution for this.

[Neeraj Dhekale]

Hello,

I am new to Nordic. Earlier I was using Cypress controllers CYBT343026-01. As per nRF documentation, I believe once the controller goes into a deep sleep mode, I cannot wake up automatically after a specific time, this was not the case in the above Cypress controller. In nRF there are other ways to wake up it from deep sleep like GPIO etc. But If I want to achieve it with a specified time, how can I do this?

Please correct me If I am wrong.

Thanks in advance

Regards,

Neeraj Dhekale

[Karl Ylvisaker]

Hello Neeraj Dhekale,

You are correct that it will require an external interrupt, like a GPIO toggling, to wake the nRF device from SYSTEM_OFF sleep. In SYSTEM_OFF sleep there is nothing enabled or working in the nRF device, so it has no possibility to wake on its own from this state. The SYSTEM_OFF sleep is the absolute lowest power consumption state. Therefore, there is no way to wake from SYSTEM_OFF sleep after a specified time using only the nRF to do so, it can not wake itself from SYSTEM_OFF.

If you enter into SYSTEM_ON sleep instead it is only the CPU sleeping, and as such you can have the RTC running to wake the CPU after a specified time has passed.
You can see the current consumption for different sleep scenarios in the sleep documentation.

Best regards,
Karl