> I was thinking about the parallel port polling idea, but then my son wanted > to measure the relation between temperature and XO frequency, so we needed > microsecond resolution.
Why do you need microsecond resolution? A junk XO will drift ballpark of 1 PPM per C. That's 86 ms per day or 3.6 ms per hour. What sort of resolution do you think you can get from a parallel port? It might be fun to see how far you can push the parallel port. How about a loop like this: Initialization: grab old time grab old parallel port data loop: grab new time grab new parallel port data if data changed: grab newer time log change that happened somewhere between old time and newer time old time = new time old data = new data goto loop Post processing can filter out the occasional samples with a wide time window because the scheduler ran some other job at the wrong time. For extra credit... Suppose you are expecting PPS type signals and you know roughly where they are located within a second. There is no point is spinning when you aren't expecting something to happen. So you can sleep until a bit before the next event. That will let the scheduler run other jobs. Hopefully it will be nicer to you when you do want to run. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.