How to enable NRF52840 to use external 32MHz crystal?

RE: How to enable NRF52840 to use external 32MHz crystal?

Turbo J — Wed, 08 Jan 2025 10:55:04 GMT

Check that your crystal is one of those mentioned in the PS. If its not, you will need to redesign the board to use one of them.

HFXAL is picky about crystals due to the rather low turn-on time.

RE: How to enable NRF52840 to use external 32MHz crystal?

Albert_0 — Tue, 07 Jan 2025 23:47:24 GMT

Hi Nick,

I'm sorry, I don't know what hardware you are using. I just copied over the code above from someone with a similar setup as mine and since it's working, I didn't look into it any more.

Sorry I couldn't be of more help.

Cheers,

Alberto

RE: How to enable NRF52840 to use external 32MHz crystal?

nick yong — Tue, 24 Dec 2024 15:56:11 GMT

thanks. Alberto

I use such code to set the extern Clock. but after run the code. I find the DK would run to right status. the extern clock is working.

But, In my own designed board. the cystal chip is different from DK. and after the code is run. I find the exten clock did not work.

HFCLKSTAT src = 0. means it is using internal clock.

what can I check now?

thanks.

RE: How to enable NRF52840 to use external 32MHz crystal?

Albert_0 — Wed, 22 Nov 2023 07:21:43 GMT

Hey Vidar Berg Turbo J

Thanks for your quick replies.

I managed to turn on the External Clock with:

/* To strictly comply with UART timing, enable external XTAL oscillator */
void enable_xtal(void)
{
	struct onoff_manager *clk_mgr;
	static struct onoff_client cli = {};

	clk_mgr = z_nrf_clock_control_get_onoff(CLOCK_CONTROL_NRF_SUBSYS_HF);
	sys_notify_init_spinwait(&cli.notify);
	(void)onoff_request(clk_mgr, &cli);
}

inside my "main()", and after checking the registers, it looks like all is set correctly.

Unfortunately I cannot use the RTS/CTS lines due to the data coming from an external device over which we have no control. Not a big deal, it's bursts of 33 bytes at 200Hz (5ms), and mostly into the micro.

I checked the error registers, actually, I check them constantly after each burst of data reception, and there are no errors.

Bottom line is, the serial interface with the active external crystal works very well and the data is received correctly. I am able to decode the stream as it's coming in and the buffer changes ok.

In terms of activating the clock, this has been resolved, thank you very much!

I want to open a new thread regarding the reading of the UARTE buffers.

Cheers,

Alberto

RE: How to enable NRF52840 to use external 32MHz crystal?

Vidar Berg — Tue, 21 Nov 2023 12:26:41 GMT

Hi,

You can request the HFXO using the "onoff" API from the clock control subsystem as we do in our Low power UART driver here : https://github.com/nrfconnect/sdk-nrf/blob/e2f09dbbc87e61b16aa18441748dafbfadc9b605/drivers/serial/uart_nrf_sw_lpuart.c#L378. But as Turbo J pointed out, the problem might simply be caused by the app being unable to keep up with the UART if flow control is not used.

Cheers

Vidar

RE: How to enable NRF52840 to use external 32MHz crystal?

Turbo J — Tue, 21 Nov 2023 10:28:02 GMT

Do you use the flow controls signals (RTS/CTS)? High baud rates require those.

Your lost characters might just be RX overflows, check if you can see the corresponding errors in the UART(E) errorsrc register.