nRF52 delay_us and delay_ms are not accurate

[mhaggag]

Hello,

I currently working with the nRF52832 chip on a custom board. The external clock is a 32MHz clock with +/- 10 ppm. When I use nrf_delay_us or nrf_delay_ms the delay is always not accurate. The following part of the code:

						nrf_gpio_pin_set(GPIO2_EXT);
						nrf_delay_ms(100);
						nrf_gpio_pin_clear(GPIO2_EXT);

Shows on the logic analyzer the following delays for different values:

nrf_delay_ms(100) ==> 96.81 ms delay nrf_delay_ms(40) ==> 38.73 ms delay nrf_delay_ms(10) ==> 9.682 ms delay

nrf_delay_us(100) ==> 95.1 us delay nrf_delay_us(40) ==> 38.2 us delay nrf_delay_us(10) ==> 9.975 us delay

Any idea whats causing this behavior or how to fix it ?

[gacekky1]

I'm not positive, but I think I remember seeing that the delay_us function is just a number of NOP's in a row. You could try adjusting this number. You would have to track down where the function is defined but you might throw it further off.

That's dang close though, personally I would just leave it unless you need a more exact delay, in which case you could set up a timer.

[endnode]

That doesn't make sense: that module is delivered in source code so you can edit it or you can rename the function and implement it in your custom module if you really don't want to touch SDK...