AVR-Chat

Something wierd is still happening..

I put some single pin diagnostics in, so that I can scope the start
and end of the A or B channel pulse measurement.
It's always taking the same time, regardless of what the input is doing!

Both the start and end of this are triggered by high edges of INT0 or
INT1, so I would expect that the observed output pulse would be
tracking the input waveform, even if it was some integer multiple,
having missed an edge or two.

Instead, the ints seem to be firing on nothing in particular..

The signals are there, on pins 16 and 17 (40 pin DIP)
Nice 5V square waves, with clean edges.

The diag pin, which is high from the detection of the first high edge,
to the detection of the second high edge, is always measuring 17.2uS.