Re: [Linuxptp-users] [Linuxptp-devel] linuxptp result doesn't match 1PPS measurement

[Miroslav L. <mli...@re...>]

On Thu, Sep 08, 2022 at 07:41:53PM +0800, Hamilton Alex wrote:
> ptp4l[130171.662]: rms    1 max    2 freq    -49 +/-   3 delay  9058 +/-   0

> my board has 1PPS output, I connect it to the master and compared with
> reference PPS.
> however,  the 1pps time error is around 40 NS, which means my board is
> ahead of the reference for about 40NS, which doesn't match the result
> dumped by ptp4l.

ptp4l is just printing the measured offset. It doesn't know the actual error.

A measured delay of 9 microseconds is huge. That's few kilometers of
cable. What hardware do you use? Does it have PHY or MAC timestamping,
and are those errors compensated? 

-- 
Miroslav Lichvar