How to configure a secondary clock crystal in Zephyr for NRF52833dk?

[Maneesh N]

Hi all,

I am trying to interface a BLE mikrobus module onto a Yocto based Linux SBC. I need to use Zephyr's hci_uart example to flash it onto the module, the mikrobus BLE module is based on nrf52833dk. But it doesn't have a primary 32.678KHz crystal, so I need to use a secondary crystal. If anyone knows how to configure a secondary crystal in Zephyr for the hci_uart example and flash it onto the module, please help me out on this.

The code works fine when I use the EVK and fails to run on the Module. If anyone can help me on how to configure a second crystal it'll really be helpful to me.

Thanks in advance.

[Sigurd]

Hi,

You need to configure it to use the internal 32.768 kHz RC oscillator (LFRC).

Set these configs:

# 32kHz clock source
CONFIG_CLOCK_CONTROL_NRF_K32SRC_RC=y
CONFIG_CLOCK_CONTROL_NRF_K32SRC_500PPM=y

[Maneesh N]

Hi Sigurd,

May I know on which file do I set this?

[Sigurd]

Try setting it in prj.conf for the hci_uart sample,

https://github.com/nrfconnect/sdk-zephyr/blob/master/samples/bluetooth/hci_uart/prj.conf

But ideally, it should be set in the board file for the custom board, so that it's applied for all samples/applications that are built.

[Maneesh N]

I tried it on the Hello world example to see if the module is able to print anything onto the console, nothing comes up on the console.

The message that I have received from the vendor of that is said "The module doesn't have 32.678KHz crystal, You need to select the secondary crystal. I mean the Internal RC Circuit".

I couldn't make much out of it. But that's what they said.