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

A C agcarver+ntp at acarver.net
Wed Aug 24 05:28:54 UTC 2011

On 8/23/2011 21:50, Mischanko, Edward T wrote:
>> -----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
>> 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
> fudge   flag2 0 flag3 1 refid PPS

I did try that before but I'll try it again and see what happens. 
However, a low going voltage should be an assert under RS232.  So this 
signal is swinging to low voltage during the pulse.

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