How to output LFCLK or its multiples?

[OYAMA YUKIO]

Hello,

I want to measure the frequency of 32.768k X'tal accurately.

I was able to output an external 32.768k X'tal to GPIO on a different CPU.  Is there such a way with nRF52840?

The frequency can be a multiple, not just 32.768k itself. I couldn't find any clock tree other than Figure.22 in nRF52840 ProductSpesification v1.7.

I couldn't get the relationship between timer and PWM time and LFCLK and its setting. Please tell me how to generate a GPIO signal frequency that has a clear relationship with LFCLK.

The ticket answers below will increase the capacitance of the XL2.

https://devzone.nordicsemi.com/f/nordic-q-a/1319/how-to-output-32768hz-external-crystal-lfclk-at-a-gpio-pin

To know the exact frequency, I need to measure without connecting anything to XL1,2.

Best Regards,

Yukio Oyama.

[OYAMA YUKIO]

Hello, Torbjorn-san.

Thank you for your answer. I will try your method.

After throwing this case, I discovered the case bellow. And I was thinking about how to do it.

https://devzone.nordicsemi.com/f/nordic-q-a/41549/test-the-accuracy-of-external-lfclk

I think it's basically the same solution, but your answer helped me a lot. I will let you know when the results come out.

Thank you.

Best regards,

Yukio Oyama