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(new to this forum, but not to electronics)

Hello,
I am looking for help with exploring different possibilities of counting puses with ZUNO.

The plan is to build a water meter, using ZUNO to count pulses from water sensor. The sensor has a very fine granularity so it outputs a many of pulses per liter. It has clean output signal (no need to debounce)

I see three options to do the counting:
* The example provided with ZUNO uses SW to count edges from the sensor. That is not good enough for me, as I can get the pulses quite close to each other.

*A better option that I find in documentation would be to use the external interrupt ZEROX. That would likely work, but I am not sure if that is always given priority when the Z-Wave is working. If not, a pulse could be missed.
Does ZEROX have highest priority and has guaranteed time to execution?

* The most elegant solution I would use on my other processor would be to use timer to count edges.
ZUNO pinout shows T0/T1 EXT CLK input, so the name suggests it has exactly what I need.However, But I can't find any documentation how to set it up.
Anybody has info or pointer to documentation about the EXT CLK pins?

Thanks,
Pavel

The highest prio is always RF, then INT1/INT0/ZEROX/T0/T1

I would suggest you to use interrupts (INT0 or INT1) as this code will be more universal and portable and will continue to work on the next Z-Uno 7gen too.

Check this: https://z-uno.z-wave.me/Reference/Interrupts/

Thanks, I have mistakenly assumed that the ZEROX will be best since it has half the fastest execution time compared to INTx. (https://z-uno.z-wave.me/Reference/zunoExtIntMode/)
I now see that it is not correct, as execution time and priority is two things. All I need is that an interrupt is processed before next one comes. 40us is enough, so I will then use the INTx as you suggested for portability reason.

But while not so much difference for the water meter case(as pulse length will be >10ms), but I am still curious about the question of what does the "T0 EXT CLK" in the ZUNO pinout diagram means and what is its intended use?

It was for external clock for T0 timer, but since 7th gen Z-Uno will not have it in that way we don't suggest to dig into

Ok, fair enough. Thanks!