32 Khz square wave in Lieu of Crystal

RE: 32 Khz square wave in Lieu of Crystal

Vincent Belaïche — Wed, 21 Jun 2023 09:10:54 GMT

Sure. Here is the new ticket.

RE: 32 Khz square wave in Lieu of Crystal

Jared — Wed, 21 Jun 2023 09:00:20 GMT

Hi Vincent Belaïche

Could you create a new ticket for this question?

regards

Jared

RE: 32 Khz square wave in Lieu of Crystal

Vincent Belaïche — Tue, 20 Jun 2023 15:24:29 GMT

Dear Jared ,

We are also considering to make a design where the nRF52840 would use for the LFCLK and external 32,768kHz square wave source from an external RTC.
We would like to know from which nRF5SDK and SoftDevice versions this combination is supported, and whether legacy BLE SDK function can be used, or migrating to the newer nrfx_… API is mandated (just in case some of the legacy functions are not fully wrapped).

One more point of interest to us is how to handle the case of an external RTC that does not provide the 32kHz clock at reset. We are considering to configure the SDK to use the internal RC oscillator by default, and then switch to the HFCLK, stop LFCLK, enable external 32kHz, and then reconfigure LFCLK to be based on external 32kHz. Do you have any opinion on this approach ?

RE: 32 Khz square wave in Lieu of Crystal

Jared — Tue, 07 Mar 2023 14:11:15 GMT

Hi Wes,

It's supported in NCS,

I'm sorry for my earlier statement about it not being supported.

regards

Jared

RE: 32 Khz square wave in Lieu of Crystal

WesC — Tue, 07 Mar 2023 13:21:53 GMT

They would be using the Softdevice Controller and NCS

RE: 32 Khz square wave in Lieu of Crystal

Jared — Mon, 06 Mar 2023 14:42:06 GMT

Hi Wes,

First, is the customer using the Softdevice Controller or the Softdevice from nRF5SDK?

On a second thought, I might have given you an outdated answer.

regards

Jared

RE: 32 Khz square wave in Lieu of Crystal

WesC — Mon, 06 Mar 2023 13:35:04 GMT

Thanks for the Reply.

I know you mentioned this has not been tested, but what is the reason the softdevice would not work with the RTC or other external source? (other than a 32Khz Crystal)

wes

RE: 32 Khz square wave in Lieu of Crystal

Jared — Mon, 06 Mar 2023 11:14:38 GMT

Hi Wes,

The nRF52840 supports using external clock such as a RTC for the LFCLK, it but the Softdevice does not, as we do not test this combination with the Softdevice.

regards

Jared