PTP PPS signal in phase with GPS signal.

[fgobber]

Hello,
I'm working with the ptp function using a Toradex board with imx8x CPU and using a linux kernel version 5.7 and linuxptp version 4.1.
The fec_ptp driver is enabled to generate a PPS signal with a frequency of 1 Hertz, this signal is used to generate actions synchronized with the PPS signal generated by the GPS.
What I see is that when the ethernet interface is connected to a grand master source, the generated pps signal is kept at a fixed distance with respect to the reference GPS source.
However, when it does not have the PTP protocol generated by the Grand Master, the PPS signal drifts.
The problem that arises is that the board's PPS signal has a random offset compared to the GPS reference signal, then in the presence of the PTP protocol this offset is maintained.
My question is how can I adjust the position of the PPS signal to keep it at the position of the GPS signal.

Thank you for your help.

Best regards.

Flavio Gobber

[a_barta]

Hello,

it seems I have the same problem in simillar way. I use 2 PTP clients connected to one grandmaster and expected the pps signals of the clients to be in phase. But this is not the case, each client is stable but the pps has a random offset to the other client. (several 100 ms)

How can I get the pps output to be in phase with the second change or with a identical, fixed offset on each client?

ptp4l[58030.729]: master offset -20 s2 freq -7689 path delay 3050
ptp4l[58031.729]: master offset 0 s2 freq -7675 path delay 3049
ptp4l[58032.729]: master offset -6 s2 freq -7681 path delay 3050
ptp4l[58033.729]: master offset -4 s2 freq -7681 path delay 3050
ptp4l[58034.734]: master offset 12 s2 freq -7666 path delay 3048
ptp4l[58035.729]: master offset 1 s2 freq -7673 path delay 3048
ptp4l[58036.730]: master offset 7 s2 freq -7667 path delay 3051
ptp4l[58037.731]: master offset -14 s2 freq -7686 path delay 3052
ptp4l[58038.731]: master offset -5 s2 freq -7681 path delay 3052

PTP seems to be stable on each client.