Disable LFXO (X2) 32.768kHz crystal

[sethu]

Hello Nordic Team, 

We had recently designed our custom nrf52840 board in which X2 or the 32.768 kHz Low-frequency crystal was not used. Can you please advise me on how to disable the LFXO crystal. I tried flashing the custom board with the development firmware which had the LFXO enabled by default but the firmware wouldn't work. 

To disable the crystal, I took the clock_skew example as a reference and tried to disable the clock within the sample using:

clock_control_off(clock0, CLOCK_CONTROL_NRF_SUBSYS_LF);

but this returns -1 due to some failure. I'm not sure how to go about with it since I couldn't find much reference.

I'm using NCS SDK v1.6.1 with Zephyr OS build  v2.6.0-rc1-ncs1

Any help would be appreciated.

Cheers, 

Sethu

[helsing]

Hello Sethu,

Try adding the following config to prj.conf:

CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y

For reference, here are the other options for LFCLK. Selecting one of these clock sources will automatically set the rest of the listed choices to '=n'.

Best regards,

Håkon

[sethu]

Thank you so much!