[ntp:questions] Fwd: Re: NetBSD GPS/PPS using 4.2.6p3

Mischanko, Edward T Edward.Mischanko at arcelormittal.com
Wed Aug 24 04:50:55 UTC 2011


> -----Original Message-----
> From: questions-
> bounces+edward.mischanko=arcelormittal.com at lists.ntp.org
> [mailto:questions-
> bounces+edward.mischanko=arcelormittal.com at lists.ntp.org] On
> Behalf Of A C
> Sent: Tuesday, August 23, 2011 8:25 PM
> To: questions at lists.ntp.org
> Subject: Re: [ntp:questions] Fwd: Re: NetBSD GPS/PPS using
> 4.2.6p3
> 
> On 8/23/2011 15:27, unruh wrote:
> > On 2011-08-23, Uwe Klein<uwe at klein-habertwedt.de>  wrote:
> >> unruh wrote:
> >>> But from his test, his system is labelling both edges.
> >>>
> >> so he has bounces on the line?
> >>
> >> either that or rise/falltime is so low and noise so high
> >> that receiver hysteris is not sufficient to  supress multiple
> >> HL/LH changes?
> >
> > No, his test shows that the line changes and then 100ms later
> it changes
> > back and 900ms later it changes again (ie once per second it
> rises and
> > falls.) Ie, it is behaving exactly as it should if it were
> detecting a
> > pulse 100ms long.It is detecting both the rising and falling
> edge.
> 
> I just checked and the pulse is almost exactly 100 ms low going
> and 900
> ms high (within about 1 ms) so it's 90% duty cycle high most of
> the time
> with a swing low.  The signal itself is clean down to microvolt
> levels.
>   The total voltage swing is about 12 volts (which would stand
> to reason
> since I'm feeding the TTL level PPS output of the GPS board
> through one
> channel of a MAX232 level shifter).
> 
> Therefore the machine is receiving a nice, clean PPS signal on
> DCD (DCD
> pin was also verified yet again and is correct by hardware
> specifications).
[Mischanko, Edward T] 
Seems like your PPS pulse is inverted?  You may want to add
Flag2 1 to your fudge line.

server          127.127.22.1
fudge           127.127.22.1  flag2 0 flag3 1 refid PPS

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