Is the use of RC oscillator suitable when system OFF?

[bloobird0]

Hello,

my custom board does not have external 32kHz crystal. I have managed to use NRF_CLOCK_LF_SRC_RC in SOFTDEVICE_HANDLER_INIT instead.

My questions are:

• what kind of limitations does the internal RC oscillator have?

• In addition to the value passed to SOFTDEVICE_HANDLER_INIT, do I have anything else to configure or manage? (I'm only using BLE, TWIS, GPIO, APP TIMER and SYSTEM OFF)

• is the usage of RC oscillator compatible with a wake up from system OFF via a pin state change?

Thanks in advance for your time and answers

[Jørgen Holmefjord]

Hi,

• You can read about the differences between external crystal and internal RC oscillator in this answer.
• You should define the temperature and calibration interval, as described in this answer.
• When putting the device in system off mode, all clock sources is turned off. The type of oscillator used does not affect this. Wake from system off will trigger a reset.

Best regards,

Jørgen

[bloobird0]

Thanks Joergen.

is there any risk of communication problem at high/low temperature even with automatic calibration? May I expect some problems by using the internal RC instead of the external XTAL (it is still possible that I make the custom board been changed)? I understand that the main benefit of the external XTAL over the RC is the reduced power, is there any other advantage?