[ntp:questions] Re: Reference clocks - which?
Richard B. Gilbert
rgilbert88 at comcast.net
Sat Oct 30 12:31:18 UTC 2004
Tapio Sokura wrote:
> Richard B. Gilbert wrote:
>> Tapio Sokura wrote:
>>> and it is working fine with an average of 1-2 satellites tracked.
>>> When the position hold feature of the GPS receiver is used, one
>>> satellite is enough for timing. Of course more is better and more
>>> reliable, but
>> I wish I knew how to do that. With NTP 4.2.0 at 1.1161-r the Oncore
>> driver seems to need 4 satellites in order to be "reachable"! As a
>> result, mine works only about thirty percent of the time. For
>> whatever reason, I get the best reception from about 9:00PM EDT to
>> about 9:00AM.
> The setup I'm using is running ntpd 4.1.1a at 1.791 on Linux 2.2.19-nano,
> I haven't bothered to update it for a while. I guess it is possible
> that there have been changes to the driver since that or maybe you are
> running a unit that doesn't have the position hold feature (I don't
> even know whether there are such Oncores)? My /etc/ntp.oncore.1 file
> looks like this:
> MODE 1
> LAT 60 3.1164
> LON 24 30.2508
> HT 28 M
> DELAY 18 NS
> CHAN 6
> TRAIM NO
> The relevant options here are MODE 1 and the three lines that follow
> it specifying the location used for position hold. I have disabled
> T-RAIM because the system seems to work better without it with only a
> couple of satellites visible. This is a home system so continuous
> reliability of the timing information is not that critical.
> ntp.conf has these two lines for my Oncore VP:
> pps /dev/oncore.pps.1 clear hardpps
> server 127.127.30.1 prefer
It seems clear that there have been a few changes to both the Oncore and
the driver. I have the Oncore M12+T.
I don't have "CLEAR" in ntp.oncore0; my Oncore uses the rising edge of
the PPS signal. I also don't have the pps line in ntp.conf. The 4.2.0
driver uses links in /dev named oncore.pps.0 and oncore.serial.0, both
pointing to the serial port. "hardpps" is still apparently an option
but now is specified using the "flag3" parameter on the server
statement. I don't use hardpps either. I will give hardpps a try.
Thanks for your response.
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