Yes, but I didn't switch inputs or diodes or did anything else to the hardware. It was working just fine with the old code but stopped working with the new code. I took a working board and downloaded the revised code. Nothing changed hardware wise, just the code. Reverted to the old version - everything OK. New code, nope.

It's got to be something in line with Darell's thinking. Previously it checked the input in a very tight loop except when it ran the servo loop which is around 350us 1500 times per second. Now it checks it a single time each time it enters the servo loop.

But if this is the case I would expect it to have missed it on ocations even with the old code. After all, it's busy ~50% of the time thus not checking the input so if an undershoot event on the signal was what caused it to work I must have been seriosult lucky since I haven't had it miss a single time.

Thanks!
/Henrik.