Measure time in mS between two pulses

[mister_e]

Rough explanation of something.

Use an interrupt to start/stop the timebase/counter. Use a fixed timebase and monitor the timer overflow. at each overflow, increment a variable.

Select a interuptable pin
Set it to rising edge
once the interrupt happen Start the Timebase/counter

At next interrupt. Stop timer and process the maths.

Overflow can be managed with an ISR.

When well done, you can have a really accurate reading in uSec precision or so. Sounds like a OlympicTimer