Accuracy issue between k_uptime_ticks() and hardware pwm outputs

Question

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?

Kyrre Aalerud · Accepted Answer

In case anyone else reads this with the same problem, yes it was possible! 
 Using a GPIOTE task channel, and assigning it's SET task address together with a timers START task address in a DPPI channel (this is nrf5340 so DPPI not PPI) with the RTC TICK event address allows for setting a pin for every clock tick, and starting the timer at same time. 
 Then connecting the timers COMPARE event to a second DPPI channel to the same GPIOTE task channel CLR task allows for clearing pin after a suitable half period that can be accurate enough for this use. 
 Finally the SHORT in the timer must be set to RESET timer and STOP timer upon COMPARE. 
 This all results in reproducing the LFCLK coming from the LF XTAL on a pin so external sensors can use this as reference and the internal RTC and systick now matches any external exactly. This completely eliminates clock drift between sensor and internal timekeeping in Zephyr.

Accuracy issue between k_uptime_ticks() and hardware pwm outputs

Top Replies