Re: Chrony not taking SOCKET data from Application

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 <[email protected]>
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 <[email protected]>
> 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-request-kWFZVVI9zxvPqho9SqqRMmD2FQJk+8+b@public.gmane.org
>> with "unsubscribe" in the subject.
>> For help email chrony-users-request-kWFZVVI9zxvPqho9SqqRMmD2FQJk+8+b@public.gmane.org
>> with "help" in the subject.
>> Trouble?  Email [email protected]
>>
>>