How to check nRF52840 CPU frequency ?

RE: How to check nRF52840 CPU frequency ?

MartinBL — Thu, 30 Mar 2017 07:06:32 GMT

You mean how you can see if it is the internal RC oscillator or the external crystal that is running? You will probably see a significant deviation from 16.000Mhz on your LED pin when running on the RC oscillator, while the crystal should be quite accurate. You can also read the NRF_CLOCK->HFCLKSTAT register to see which clock source you are using. One of them is always being used when the CPU is doing something.

RE: How to check nRF52840 CPU frequency ?

madhu — Thu, 30 Mar 2017 06:20:21 GMT

Thank you Martin, I have toggled an LED directly writing in to the registers, putting in a while loop and I am able to see 16MHz clock. But how can I make sure that HFCLK of 64MHz is enabled or not??

RE: How to check nRF52840 CPU frequency ?

MartinBL — Tue, 28 Mar 2017 14:58:01 GMT

Hi,

The best way is probably to use a timer, PPI, and a GPIOTE channel to toggle a pin. The Timer base frequency is 16MHz so that means you can toggle a pin at 16MHz, and get an 8MHz signal out that you can measure on. The timer and CPU use the same system clock so this should give you what you need.