[ntp:questions] pps breaks when nmea is enabled for ntpd

Richard Cagley rcagley at gmail.com
Sun Jun 16 00:37:42 UTC 2013


hmm, timeX is just a calibration factor so I don't think adding it will fix
my pps breakage. But, I do think it's important and I'm not using it.

So, question to you, I have a U-Blox NEO-6P module. How would I go about
determining the time1/time2 values for the 127.127.20.0 server? The key
words "offset" and "calibration" don't show up here
http://www.u-blox.com/images/downloads/Product_Docs/NEO-6_DataSheet_%28GPS.G6-HW-09005%29.pdf



On Sat, Jun 15, 2013 at 8:54 AM, David Lord <snews at lordynet.org> wrote:

> Richard Cagley wrote:
>
>> I have a TI DM8168 processor and a u-blox gps.
>>
>> If I enable an internet server and pps, then pps works great
>>
>> server clock.redhat.com iburst prefer minpoll 4 maxpoll 4
>> server 127.127.22.0 minpoll 4 maxpoll 4
>> fudge 127.127.22.0 flag3 1
>>
>> However, if I add an NMEA server to my ntp.conf file like this
>>
>> server 127.127.20.0 mode 1
>> fudge 127.127.20.0 flag1 1
>> server 127.127.22.0 minpoll 4 maxpoll 4
>> fudge 127.127.22.0 flag3 1
>>
>> then pps stops working. I can kill ntpd and ppstest no longer works. It's
>> as though nmea is clobbering the serial port.
>>
>> It sorta feels like this, but there was no resolution
>> http://lists.ntp.org/**pipermail/questions/2011-**September/030347.html<http://lists.ntp.org/pipermail/questions/2011-September/030347.html>
>>
>> Can anyone help me. I've really been struggling with this.
>>
>
> I'm using NetBSD-6.1 ntpd 4.2.6p5 but have also had pps + nmea
> working on ubuntu.
>
> You probably need to determine then add time2 0.xyz sec to
> your config. The time2 value is for your particular gps and
> gps firmware version.
>
> For my "Sure" gps I have:
>
> server 127.127.20.2 mode 18 prefer
> fudge  127.127.20.2 stratum 4 time2 0.417 flag1 0 refid GPSb
> server 127.127.22.2
> fudge  127.127.22.2 flag2 0 flag3 1 refid PPSb
>
> From peer summary I have:
> 127.127.22.2 mean=0.000 rms=0.004 max=0.038
>
> The 0.038 is mostly due to load from two cron jobs each evening.
>
>
> David
>
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