[ntp:questions] Re: 1pps signal,20us width

Fei Wu fxw115 at yahoo.com
Mon Nov 15 21:26:18 UTC 2004


thanks Steven.

It is FreeBSD 5.1, I do not have similar problem with
other boxes.

I used black box RS232-485/422 converter. I watched
the signal using ocsilliscope, it is clean +-12V
signal. However, the signal is distorted(rounded) a
little at rising upper left edge. Is it a problem?

Fei

--- rtxo <gnu at wraith.sf.ca.us> wrote:

> Fei Wu wrote:
> 
> > I tried not to stretch the PPS pulse and feed it
> into
> > RS232 port ( my pc like server ). I got the
> following
> > error:
> >  refclock_atom: time_pps_kcbind failed: Operation
> not
> > supported.
> 
> This seems like your kernel is not an RFC2783
> (ppsapi)
> capable system. Linux needs the "PPSKit" patch, and
> freebsd 4.x should support ppsapi.
> 
> (...)
> 
> > Does the error confirms that the pulse is too
> short
> > for my machine?
> 
> No, it sounds like your kernel is the problem.
> Also, you should make sure that the TTL signal has a
> proper level converter to the rs232 signal levels,
> for
> best compatibility with pc motherboards. An MC1488
> will
> work best. A MAX232 will also work, but adds a
> minimum
> of 1.5 microseconds latency.
> 
> ../Steven
> _______________________________________________
> questions mailing list
> questions at lists.ntp.isc.org
> https://lists.ntp.isc.org/mailman/listinfo/questions
> 



		
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