How to measure 32.768 kHz frequency?

[JB21]

I want to measure the accuracy of the 32.768 kHz oscillator.

Is there a way to output it on a port-pin, even when it comes out via a divider?

I can't touch the crystal as it would change the loading.

[JB21]

Many thanks for your answers.

I had some problems getting Krzysztof's suggestion to run. While searching more I found my question already answered, I didn't find it in an earlier search. That works quite well.

I only added as the first line:

NRF_CLOCK->LFCLKSRC= (CLOCK_LFCLKSRCCOPY_SRC_Xtal << CLOCK_LFCLKSRCCOPY_SRC_Pos);

[eiadj]

Which solution did you find to work the best? What were the issues with Krzysxtof's method? 

We're currently doing the same measurement on the xtal, any info would be greatly appreciated!