Hi Axel,
On 10/3/22 21:23, Axel Simon wrote:
Your subject has "disciplined oscillator" in it. That sounds like you want
ptp4l to carry the time forward while there is no GPS reception. Thus, it seems that you
have a setup where your GPS receive does not have a lock to GPS at all times.
Not quite. But perhaps my explanation wasn't sufficient. What I have is
an external device that is GPS synced and has 10MHz/1PPS output. Even if
it's not GPS locked, the oscillator is much better and so the 1PPS
output will be stable.
What I am actually interested in is using the 1 PPS reference and
discipline the NIC's oscillator.
I am still not quite sure to which extend this would improve the
timestamp accuracy.
We found that ptp4l can only synchronize NIC clocks (e.g. i210) to an accuracy
of ~2µs due to the latency PCIe transactions. If you want better
synchronization, ptp4l with off-the-shelf NICs is not a solution.
Interesting. For my application (telecom) I definitely need accuracy in
the range of 1.5us.
In your statement, are you referring to off-the-shelf NICs acting as
slaves or master?
Also, are you referring to unmodified off-the-shelf NICs or modified,
i.e. disciplined or equipped with higher quality oscillators?
Thanks
Andre
Cheers,
Axel
However, making a reliable GM product is quite a bit of work. The PTP
software stack is only one piece of the puzzle.
Yes of course. This effort is just to develop a poor man's GM as a PoC.
But nonetheless interesting to observe that there is practically no NIC out
there that brings together all the pieces. Should be quite easy to do. Cards
like the Intel XXV710-DA2T or E810-XXVDA4T with GPS input are hard to get and
$$$.
Thanks
Andre
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