Accuracy issue between k_uptime_ticks() and hardware pwm outputs

[Kyrre Aalerud]

Running into a slight issue where the timebase for system (reference time + uptime aka k_uptime_ticks()) drifts relative to sensor sampling rates.
Attempt to synchronize the timebases by using nRF53 pwm system to output clock for external sensors still drifts as the timebase for pwm appears to be HFCLK based of HF XTAL while system ticks come from LFCLK based of LF XTAL.

What is the recommended method to synchronize these while keeping power consumption low?
CONFIG_CLOCK_CONTROL_NRF_K32SRC_SYNTH may be an option but how will this impact power consumption, and will it prevent sleep?

[Simonr]

Hi

Using the pins for XL1 and XL2 as both GPIOs and clock pins won't be possible as far as I'm aware. How low do you require to keep the power consumption exactly? This will be a trade-off between the need for accuracy versus the need for low power consumption I think. Using the K32SRC_SYNTH source as the LF clock source will definitely be the most accurate way, but it will also keep the HF clock on when using the LF clock, so it will affect the power consumption quite a bit. Using a more accurate LF XTAL could also be an option, if you find a "high-end" 32.768kHz crystal for your design with a lower PPM drift that might be an idea to keep it accurate but also at low power.

Best regards,

Simon

[Kyrre Aalerud]

I am using a quite good LF XTAL but the external sensor uses a (rather poorly) calibrated internal oscillator unless I can feed it a better reference. When I tried using the SYNTH option BLE connections would fail to complete although unit was still discoverable.