Hi Miroslav Lichvar, Can I use pps directive to a PPS refclock? refclock PPS /dev/pps1 poll 0 pps lock GPS refid PPS trust prefer
Will this increase the accuracy? I am using below refclocks: refclock PPS /dev/pps1 poll 0 lock GPS refid PPS trust prefer refclock SOCK /var/run/chrony/udssocket.sock poll 0 refid GPS noselect As we are using GPS and 1PPS, our assumption is chrony synchronizes system clock with nanosecond level accuracy. Am I right on this? But we see microsecond level accuracy even after using makestep directive. Thanks & Regards Sarveshwar.K On Mon, Feb 20, 2023 at 3:56 PM sarveshwar k <sarveshwar...@gmail.com> wrote: > Hi Miroslav, > > Thanks for the information. > > >My question would be, why do you need the system clock to be so > >accurate? The CPU is connected to the outside world over PCIe, which > >has latency and possibly also asymmetry in hundreds of nanoseconds. > >What do you do on that computer that this accuracy would make a > >difference? > This system clock is being used by other applications like IMU sensor data > timestamping. > We are having this chrony running in an ECU (Electronic Control Unit) > along with PTP stack to send PTP packets to other ECUs in the network to > get synced to Master ECU. > > Thanks & Regards > Sarveshwar.K > > On Thu, Feb 16, 2023 at 1:59 PM Miroslav Lichvar <mlich...@redhat.com> > wrote: > >> On Thu, Feb 16, 2023 at 10:04:02AM +0530, sarveshwar k wrote: >> > Is it not possible to achieve synchronization accuracy less than 100ns >> with >> > chrony (with GPS and 1PPS). >> >> With HW timestamping of the PPS signal (e.g. on the I210) it is >> possible, but difficult to verify. >> >> My question would be, why do you need the system clock to be so >> accurate? The CPU is connected to the outside world over PCIe, which >> has latency and possibly also asymmetry in hundreds of nanoseconds. >> What do you do on that computer that this accuracy would make a >> difference? >> >> > Can we configure chrony behaving as a measurement tool (not to make any >> > corrections)? >> >> There is the chronyd -x option or the refclock noselect option for >> that. >> >> -- >> Miroslav Lichvar >> >> >> -- >> To unsubscribe email chrony-users-requ...@chrony.tuxfamily.org >> with "unsubscribe" in the subject. >> For help email chrony-users-requ...@chrony.tuxfamily.org >> with "help" in the subject. >> Trouble? Email listmas...@chrony.tuxfamily.org. >> >>
