Hi Simon,

if the ring burst was 1s and the next burst follow after 4s,
then you want to stay in the interrupt routine for more than 1s ???
Thats definitively not the meaning of an interrupt !

Interrupt handler must be very short to let the main program working continously.

So you need another approach:

You establish an timer interrupt, which give you an 1s clock.
The external interrupt increment only a counter.

Then the timer interrupt can read and reset this counter every 1s.
E.g., if less than 5 pulses count, it was detect as pause and if more than 10 pulses count it was detect as burst.
So short noise pulses can not influence your burst detecting.
Also your interrupt handler was very short.

Please watch, that the 1s clock was asynchroneous to the ring burst. So it can be, you have detect 2 bursts without a pause between, which must then be counted as a single bust.


Try ever, to do all no time critical things outside the interrupt.
If you must wait longer, try to find a method to leave the interrupt during this wait time.
All wait times above 100µs should be done outside the interrupt.


Peter