[ntp:questions] Assistance with PPS on Windows
unruh at wormhole.physics.ubc.ca
Thu May 5 00:11:55 UTC 2011
On 2011-05-04, Ken Link <klink at numberzero.org> wrote:
> It appears all I needed to do was swap the TX and CD pins to get it to
> start polling and synced to PPS. Thanks!
> Now, a behavioral question. Will PPS be selected as the peer if and
> only if the peer marked "preferred" is also synced? What if I want PPS
> to act as a supplement to whichever of the stratum 1+ peers NTP sees
> available and decides to sync to? PPS will be the only stratum 0
> reference source available to this system, but if the preferred peer
> goes down I would expect PPS to continue to correct the jitter of
> whichever other peer NTP decides to sync to (that doesn't seem to be
> the case).
> Also, it appears that while the preferred peer continues to be synced
> and polled every 64 seconds, the PPS peer seems to "toggle" from being
> a PPS peer to being rejected nearly every poll (of 16 seconds). Is
> this because the polling rate is different between the PPS source and
> the other sources, or is my serial cable too jittery? The PPS source
> claims to have an offset of +/- 10 ms and a jitter of between 2-3 ms
> depending on the poll.
Did you mean usec or do you really mean milliseconds? Not a great PPS
> On Wed, May 4, 2011 at 2:11 PM, Ken Link <klink at numberzero.org> wrote:
>> Cool program. We've got a physical adapter that does the same thing.
>> We're using DB9-to-RJ45 adapters throughout our serial network and it
>> appears I'm not using the correct RJ45-to-DB9 adapter to move the PPS
>> signal to the DCD pin. I'll post back when I make the right adapter
>> and get a chance to test again.
>> That would probably explain why ntpd is seeing a 413279.091756s offset, huh.
>> On Wed, May 4, 2011 at 9:56 AM, David J Taylor
>> <david-taylor at blueyonder.co.uk.invalid> wrote:
>>>> The problem is we cannot get NTP to sync to the PPS output. The PPS
>>>> source shows up in ?ntpq ?p? however it has 0 reach. System B is
>>>> synced to System A and is a stable Stratum 2 server at the moment.
>>>> MbgMon on System B shows the PPS output on the card is active. The
>>>> IRIG signal is 100% and shows it is synced. I?ve installed the
>>>> serialpps driver, rebooted and verified it was loaded in the Device
>>>> Manager, set the PPSAPI_DLLS global environment variable
>>>> appropriately, etc.
>>>> Any suggestions on how to troubleshoot this?
>>> Ken, Dave Hart is the expert in the PPS on Windows. ?Could I suggest that
>>> you at least check that the pulses are being seen by checking with my Serial
>>> Port LEDs program?
>>> With NTP not running (as only one device can access the COM port), see
>>> whether there are brief white flashes on the DCD line.
>>> questions mailing list
>>> questions at lists.ntp.org
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