[ntp:questions] Jitter on $GPGGA of Sure board

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Tue Mar 20 23:56:51 UTC 2012


I'm curious.  Are you outputting ONLY GPGGA, or other sentences as 
well.  Other sentences will increase jitter.  I'm getting about 5 ms of 
jitter on my USB based BU-353 outputting GPGGA only at 9600 baud.  I'll 
be testing the Sure board once I get it.

Sincerely,

Ron

On 3/20/2012 4:32 PM, Gom wrote:
> Hi,
>
> I've been working on my own clock management software under windows 
> using a Sure board, without the serialpps driver.
>
> Here's some console output
>
> Lines with "offset" are the PPS
> The other lines are from the $GPGGSA.
>
> You can see the PPS maintains the offset of the windows clock under 30µs.
>
> You can also see that the $GPGGA is decoded between milliseconds 388 ( 
> I've seen 370) and 426, so providing a rough jitter of 50 ms.
>
>
>
> 20:22:56.999.839.3      PerfCntScale:   0.99977860      offset: 20.8 us
> 20:22:57.426.863.8      LastUpdate:     0.426950 s
> 20:22:57.999.896.5      PerfCntScale:   0.99978054      offset: 9.6 us
> 20:22:58.413.920.2      LastUpdate:     0.414011 s
> 20:22:58.999.953.7      PerfCntScale:   0.99978233      offset: -15.8 us
> 20:22:59.420.995.8      LastUpdate:     0.421092 s
> 20:22:59.999.053.6      PerfCntScale:   0.99978417      offset: 9.8 us
> 20:23:00.421.077.8      LastUpdate:     0.421164 s
> 20:23:00.999.110.9      PerfCntScale:   0.99978610      offset: 2.2 us
> 20:23:01.421.135.0      LastUpdate:     0.421231 s
> 20:23:01.999.168.1      PerfCntScale:   0.99978789      offset: -16.4 us
> 20:23:02.420.210.1      LastUpdate:     0.420305 s
> 20:23:02.999.268.0      PerfCntScale:   0.99978966      offset: 6.6 us
> 20:23:03.420.292.2      LastUpdate:     0.420383 s
> 20:23:03.999.325.3      PerfCntScale:   0.99979145      offset: -9.7 us
> 20:23:04.424.367.7      LastUpdate:     0.424457 s
> 20:23:04.999.425.2      PerfCntScale:   0.99979326      offset: 22.1 us
> 20:23:05.425.449.6      LastUpdate:     0.425525 s
> 20:23:05.999.482.5      PerfCntScale:   0.99979498      offset: 2.2 us
> 20:23:06.412.506.1      LastUpdate:     0.412598 s
> 20:23:06.999.539.7      PerfCntScale:   0.99979679      offset: -5.7 us
> 20:23:07.416.581.3      LastUpdate:     0.416660 s
> 20:23:07.999.639.6      PerfCntScale:   0.99979844      offset: 14.7 us
> 20:23:08.431.664.4      LastUpdate:     0.431744 s
> 20:23:08.999.696.9      PerfCntScale:   0.99980012      offset: -3.2 us
> 20:23:09.410.737.9      LastUpdate:     0.410813 s
> 20:23:09.999.796.8      PerfCntScale:   0.99980178      offset: 21.8 us
> 20:23:10.411.820.4      LastUpdate:     0.411890 s
> 20:23:10.999.854.1      PerfCntScale:   0.99980350      offset: 10.7 us
> 20:23:11.406.877.4      LastUpdate:     0.406956 s
> 20:23:11.999.911.3      PerfCntScale:   0.99980516      offset: -3.8 us
> 20:23:12.422.953.5      LastUpdate:     0.423034 s
> 20:23:13.000.011.2      PerfCntScale:   0.99980684      offset: 27.1 us
> 20:23:13.428.035.8      LastUpdate:     0.428100 s
> 20:23:13.999.068.4      PerfCntScale:   0.99980834      offset: 0.6 us
> 20:23:14.420.092.5      LastUpdate:     0.420180 s
> 20:23:14.999.125.6      PerfCntScale:   0.99981007      offset: -3.5 us
> 20:23:15.428.168.5      LastUpdate:     0.428244 s
> 20:23:15.999.225.6      PerfCntScale:   0.99981153      offset: 11.6 us
> 20:23:16.431.250.3      LastUpdate:     0.431338 s
> 20:23:16.999.282.8      PerfCntScale:   0.99981310      offset: -4.2 us
> 20:23:17.406.323.5      LastUpdate:     0.406394 s
> 20:23:17.999.382.8      PerfCntScale:   0.99981468      offset: 25.1 us
> 20:23:18.418.406.8      LastUpdate:     0.418467 s
> 20:23:18.999.440.0      PerfCntScale:   0.99981619      offset: 6.8 us
> 20:23:19.406.463.3      LastUpdate:     0.406539 s
> 20:23:19.999.497.2      PerfCntScale:   0.99981772      offset: -8.3 us
> 20:23:20.418.539.1      LastUpdate:     0.418616 s
> 20:23:20.999.597.2      PerfCntScale:   0.99981926      offset: 22.0 us
> 20:23:21.418.621.2      LastUpdate:     0.418683 s
> 20:23:21.999.654.4      PerfCntScale:   0.99982073      offset: 3.0 us
> 20:23:22.403.677.5      LastUpdate:     0.403758 s
> 20:23:22.999.711.6      PerfCntScale:   0.99982223      offset: -9.9 us
> 20:23:23.418.753.5      LastUpdate:     0.418829 s
> 20:23:23.999.811.6      PerfCntScale:   0.99982367      offset: 15.2 us
> 20:23:24.415.835.4      LastUpdate:     0.415908 s
> 20:23:24.999.868.8      PerfCntScale:   0.99982510      offset: -2.5 us
> 20:23:25.397.908.6      LastUpdate:     0.397975 s
> 20:23:25.999.968.8      PerfCntScale:   0.99982656      offset: 27.2 us
> 20:23:26.397.991.6      LastUpdate:     0.398043 s
> 20:23:26.999.026.0      PerfCntScale:   0.99982800      offset: 12.7 us
> 20:23:27.388.048.2      LastUpdate:     0.388113 s
> 20:23:27.999.083.2      PerfCntScale:   0.99982938      offset: -4.7 us
> 20:23:28.409.124.1      LastUpdate:     0.409191 s
> 20:23:28.999.183.1      PerfCntScale:   0.99983078      offset: 22.6 us
> 20:23:29.388.205.4      LastUpdate:     0.388258 s
>
>

-- 

(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such.  I don't always see new messages very quickly.  If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)

Ron Frazier
timekeepingdude AT c3energy.com



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