External crystal oscillator clock signal is intermittent during bluetooth working in nrf52833

[iamcfc]

I was using nrf52833 for AOA test. The example works quite good, but we found external crystal oscillator clock signal is intermittent. I want to know if cpu will go into sleep mode in AOA advertising and scanning, and if entering sleep mode will change the clock source. If the clock source is changed, how can I prevent this situation. Thanks.

[Edvin]

Hello,

Is there a particular reason you need the XTAL to be on at all times? The reason it is turned off is to save power. If you want it to be turned on at all times, you can do so from your application, but be aware that this will affect the current consumption.

BR,

Edvin

[iamcfc]

we want to try keep the XTAL to be on at all times to see if it can make the clock more stable, and maybe AOA test will have  better results, but now I do not know how to set it. The current consumption is no need to worry about for the moment. Thanks.

[Edvin]

I assume you are using the nRF Connect SDK (NCS) and not the nRF5 SDK? Please let me know. Assuming you are using NCS:

To keep the HF clock running, I suggest you look into Zephyr's clock control API.

https://github.com/nrfconnect/sdk-nrf/blob/main/samples/peripheral/radio_test/src/main.c#L11-L41

This should ensure that Zephyr doesn't shut off the clock when the BLE stack is done using it.

That being said, I am not convinced this will make any difference, other than a higher current consumption. I don't know what you mean by "better test results". What sort of issues are you seeing? The HFCLK is not used for timekeeping. That would be the LFCLK. But the HFCLK is used by the BLE stack. However, I have not seen a similar request before, so, therefore, I am not sure whether this will make any difference.

Best regards,

Edvin

[iamcfc]

Thanks, I will try the api.

The reason why I want to do this is when I test AOA results, the phase bias of the reference data is not stable and my colleague think maybe the on and off of the clock will affect the results, so I think I can try not to shut off the clock and test.

[Edvin]

Hello,

If you are struggling with the HF Clock, I suggest that you also upload your HW schematics and PCB layout in another ticket, and ask for a layout review. They can check whether the XTALs are connected correctly (with the correct capacitors and so on). I am sorry, but that is not my area of expertise, so I can't help you with that.

BR,
Edvin