Custom board crystal, is it working ?

[consulting99]

How do I quickly check if the external crystal  (32.768 with 15pf load caps.)  I soldered is working.

I built a custom board but had to reflow solder in my lab.

Everything is perfect, examples run .

Is there a function I can call that would return true/false? 

Like in some AVR microcontroller , is it possible to send the clock output to a pin where I can measure the clock frequency ?

[Håkon Alseth]

Hi,

 

How do I quickly check if the external crystal  (32.768 with 15pf load caps.)  I soldered is working.

I built a custom board but had to reflow solder in my lab.

Everything is perfect, examples run .

Is there a function I can call that would return true/false? 

Like in some AVR microcontroller , is it possible to send the clock output to a pin where I can measure the clock frequency ?

If your application does not start up the LFCLK, you can manually start up the 32k ext. clock:

NRF_CLOCK->LFCLKSRC = (CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos);
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
NRF_CLOCK->TASKS_LFCLKSTART = 1;

while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0) {}
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;

 

Add this to the blinky example for instance, and if it hangs in the while-loop, it has problems starting up your external 32k source.

 

If using a example that has already started the 32k source, you can also read the status in this register:

https://infocenter.nordicsemi.com/topic/ps_nrf52840/clock.html?cp=4_0_0_4_3_2_18#register.LFCLKSTAT

 

Kind regards,

Håkon