RE: nRF5340 Low frequency Clock configuration when external clock is used

Riccardo Gaiati — Tue, 21 Jan 2025 10:03:17 GMT

Thanks a lot !

RE: nRF5340 Low frequency Clock configuration when external clock is used

Priyanka — Tue, 21 Jan 2025 09:52:01 GMT

The LFXO and HFXO can be configured via the dts as mentioned here in the release notes: Migration guide to Zephyr v4.0.0 — Zephyr Project Documentation

RE: nRF5340 Low frequency Clock configuration when external clock is used

Riccardo Gaiati — Tue, 21 Jan 2025 08:43:08 GMT

Hi Priyanka,

sorry for the late reply. Thanks for the information.

Do you have any news regarding the question 3 ?

Thanks in advance !

RE: nRF5340 Low frequency Clock configuration when external clock is used

Priyanka — Mon, 02 Dec 2024 13:58:13 GMT

Hi Riccardo,

[quote user=""]By activating the BYPASS, what is really bypassed (see picture below)? [/quote]

When enabling the BYPASS, generally the internal LFXO circuit is bypassed, and Instead, the SoC directly uses the external clock signal applied to the XL1 pin as the source for the LFCLK.

[quote user=""]I suppose i dont need to use any capacitor in this configuration. Is it correct to set the XOSC32KI.INTCAP as by default ?[/quote]

No, you wouldn't need any caps since the LFXO circuit is completely bypassed. Yes, you can set the XOSC32KI.INTCAP as default.

[quote user=""]So far, I have run the above scenario WITHOUT enabling the BYPASS. The device seems to work anyhow. Is that expected ?[/quote]

Well, it's recommended to enable BYPASS when using an external clock source. If the external signal is within the expected frequency and voltage range, the internal oscillator circuit might sometimes appear to work, but it is not a guaranteed/stable state.

[quote user=""] In case the external source is removed or fails, what is the behaviour of the clock peripheral ? any fall-back behaviour ?[/quote]

I don't think there's any default failsafe / fallback mechanism and the LFCLK will just stop work in case of a failure. But you can always create your own fallback method using a watchdog or interrupt etc.

I am checking internally for the other queries and will get back to you soon.

-Priyanka