On Mon, Jun 25, 2018 at 02:43:27PM +0100, Richard Hill wrote: > 1. The hardware nanosecond counter is not the same as PTP nanoseconds. PTP > time is held as > a variable, not by FEC
You can and should use timecounter_cyc2time() to convert raw cycle counts into PTP time. > 2. The PPS-OUT signal does fire each second, but is not necessarily aligned > to PTP 0 > nanoseconds Looks like the driver's author neglected the frequency adjustment on the PTP time when setting the interrupt. > 4. To get sub 100ns accuracy, you're likely going to need external hardware > to control the > system clock by measuring the difference between GPS-PPS and PPS-OUT. (You > can then do > fine adjustment of PTP time) Forget about the "pps". You don't need it for implementing a GM. All you need is the 1-PPS signal from the GPS into the FEC. Then you can serve the GPS time via PTP. The Linux system time is irrelevant in this case. HTH, Richard ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
