How to measure the start up time of HXFO for nRF52?

[Hsu]

Hi Sir,

According the table 19.4.2 of 52832 datasheet (v1.4), there is a start up time (0.36 ms) for HXFO.

How do I measure the start up time of my 32M crystal?

If the measure value doesn't meet the 0.36 ms, any side effect?

Thank you.

BRs, Han

[bjorn-spockeli]

Hi Han, 

toggle a GPIO pin before starting the HF clokck and then  wait for the EVENTS_HFCLKSTARTED event and then toogle the GPIO again, i.e. 

//Toggle GPIO

//Start HFCLK
NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;

NRF_CLOCK->TASKS_HFCLKSTART = 1;

while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

// Toggle GPIO here or tie the EVENTS_HFCLKSTARTED to a GPIO using PPI

and then use a logic analyzer to measure the time it took. The values stated in the Product Specification are typical values so expect some variation from device to device. 

Best regards

Bjørn 

[Hsu]

Hi Bjorn,

Thanks for the update, will try for this.

BRs, Han