PWM Jitter with nRF52DK

RE: PWM Jitter with nRF52DK

Susheel Nuguru — Thu, 06 Feb 2025 12:38:08 GMT

Also , if you are using a BLE or other protocol stacks, they turn on the hfclk as needed but in your example, since you are not using BLE or any other stack, the responsibility to start the right clocks falls on the applicaiton.

RE: PWM Jitter with nRF52DK

Susheel Nuguru — Thu, 06 Feb 2025 12:37:04 GMT

I think you need to know your peripherals to understand which clocks they work with. With PWM, the peripheral itself can work with both internal and external clocks but it is recommended to use XTAL HFCLK. This has been discussed on the forum like here. Unfortunately there is no single source to find such information as this is scattered info.

RE: PWM Jitter with nRF52DK

Moe1992 — Wed, 05 Feb 2025 16:24:34 GMT

Thank you :) I did find a forum post which suggests using this pice of code:

NRF_CLOCK->TASKS_HFCLKSTART = 1;
// Wait for clock to start
while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

and I am happy to say that this works.

But since I am still learning, I would like to know, how I could have found this solution if nobody had asked this before here on the forum. What I mean is: How do I find this information using the documentation? Searching "HFXO" in the nRF Connect SDK documentation yields no results: https://docs.nordicsemi.com/search?bundle=ncs-latest&labelkey=nrf52832&labelkey=nrf52-series&q=hfxo

Why does nothing show up in the results?

Thank you

RE: PWM Jitter with nRF52DK

Daniel Chisholm — Wed, 05 Feb 2025 14:28:38 GMT

Try enabling the high frequency crystal oscillator (keyword "HFXO" shoud help you find things).

If HFXO isn't turned on, then the internal 32MHz RC oscillator is used.