On Wed, Oct 19, 2016 at 11:15 PM, Ilia Platone <i...@iliaplatone.com> wrote:
> I need to know how much precise this system can be. How much resolution > can I obtain with a cheap receiver (maximum quantization frequency)? > Formulas are well accepted. Even a cheap receiver will have error that is orders of magnitude smaller then the resolution that the linux kernel can work in. You should expect the system time to have error on the order of about 10 microseconds The PPS signal error comping out of events low cost GPS receiver has error oon order of say a few tens of nano seconds, that is 100 to 1000 times less error The major source of error is not GPS , but is the interrupt latency uncertainty. But this is not bad at all, you can expect roughly a 10 microsecond uncertainly in the time stamps more or less. But a lot depends on how you handle the second GPIO interrupt. the GPS interrupt is handled inside a kernel level handler. The handler snap shots the system clock and stores it in RAM, then sets a flag that the user space process checks. Does your GPIO interrupt have a kernel level driver to snapshot the system clock ir is this happening in a user space process? If the later expect worse performance. For best performance copy and paste the Linux PPS code and then re-build the Linux kernel with your new driver. Getting event time stamps much better then this requires some purpose built hardware outside of the computer. Chris Albertson Redondo Beach, California _______________________________________________ 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.