FreeRTOS time anomalie?

[enGaryN]

My program measures the exact time between two events (interrupts) with microsecond accuracy. Every 17.8 seconds the measurements are distorted by several hundred microseconds. Has anyone encountered such behavior of FreeRTOS?

[MicroController]

At 240MHz, the 32 bit CPU cycle counter overflows every 17.89 seconds. Coincidence?

[dmitrij999]

What kind of timer for microseconds checking you use?
If it's the hardware timer, then it could be interrupts priorities: systick timer may have the highest interrupt priority.
What's the original purpose to account microseconds?
For flow counter I used PCNT

[enGaryN]

At 240MHz, the 32 bit CPU cycle counter overflows every 17.89 seconds. Coincidence?

This is obvious. Common place

[enGaryN]

What kind of timer for microseconds checking you use?
If it's the hardware timer, then it could be interrupts priorities: systick timer may have the highest interrupt priority.
What's the original purpose to account microseconds?
For flow counter I used PCNT

I use esp_timer_get_time() function.
Original purpose is soft PLL for incoming periodic sequence.
Can PCNT provide microsecond (~10us) accuracy?

[MicroController]

Do you need to match only the frequency or also the phase?

[enGaryN]

Do you need to match only the frequency or also the phase?

Phase (the exact time beetwen local and remote periodic events) is a fundamentally important and is the main goal of measurements

[dmitrij999]

I use esp_timer_get_time() function.

That's the reason
esp_timer is driven the software way within FreeRTOS, so due to some hardware spinlocks FreeRTOS scheduler may be locked.
I used PCNT for pulse counting.
For your purpose i'd advise you to check with hardware timer, I think it's the high-accuracy timer so it allows to account microseconds.

[enGaryN]

I use esp_timer_get_time() function.

That's the reason.

You're right.
I found a simple intermediate solution:
using cpu_hal_get_cycle_count() function (paired with _set_) instead of esp_timer_get_time()

Thanks everyone!

UPD: hardware timer also works well