[ntp:questions] problem with ntpd refclock and pps via parallel port

David Lord snews at lordynet.org
Mon Feb 1 22:20:42 UTC 2010

unruh wrote:
> On 2010-02-01, David Lord <snews at lordynet.org> wrote:
>> unruh wrote:
>>> On 2010-01-31, David Lord <snews at lordynet.org> wrote:
>>>> problem with ntpd refclock and  pps via parallel port
>>>> Hi
>>>> So does pps really need a refclock and/or does pps via
>>>> parallel work ok or not on NetBSD-5?
>>> Yes. Otherwise it has no idea what the seconds is. Ie, all pps does is
>>> deliver a pulse at the exact second boundary, but that says nothing
>>> about which second that is the boundary of. You need some other source
>>> to give you the seconds.
>> Sorry, I missed mention of the local ntp peers.
>> There were three local servers to give time to second, one being
>> a pool server with radioclock that I was attempting to distribute
>> pps from via parallel port. Docs I have indicate a server can be
>> used to get "second" in place of refclock,
> Yes, it certainly can. However you should make sure that your system is
> within a half second of the correct time before starting the PPS.
> Otherwise the PPS will just take the current seconds, and lock you onto
> a time which is out by seconds.

Now I han have another play with this I find that I must
have still been on serial DCD since disconnect of parallel
lead made no difference. Symlink was pps0 -> lpt0 and I
was sure I'd restarted ntpd ok before going to bed late
this morning. Now a restart gives the configuration failed
and no PPS.

I've moved symlink back to pps0 -> tty00 and ntpd restarted
this time with minpoll 4.

I'll go back to playing with lpt port for another day. I'd
just expected it to work.


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