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

Gom gom at gom.invalid
Wed Mar 21 08:49:07 UTC 2012


Only $GPGGA.

I changed things slightly, in previous version time was queried when 
$GPGGA was found after some processing, now it is queried as soon as the 
serial port interrupt arrives.

Serial interrupt arrived between 267 ms and 320 ms, still providing a 50 
ms jitter.

08:46:04.267.945.0      LastUpdate:     0.268265 s
08:46:05.000.018.2      PerfCntScale:   0.99997059      offset: 24.2 us
08:46:05.277.034.1      LastUpdate:     0.277070 s
08:46:05.999.075.4      PerfCntScale:   0.99997054      offset: 5.3 us
08:46:06.297.092.4      LastUpdate:     0.297696 s
08:46:06.999.132.6      PerfCntScale:   0.99997099      offset: 36.6 us
08:46:07.295.149.5      LastUpdate:     0.295680 s
08:46:07.999.189.8      PerfCntScale:   0.99997041      offset: -33.9 us
08:46:08.277.217.6      LastUpdate:     0.277788 s
08:46:08.999.289.8      PerfCntScale:   0.99997047      offset: 0.6 us
08:46:09.287.306.3      LastUpdate:     0.288098 s
08:46:09.999.347.0      PerfCntScale:   0.99997045      offset: -15.5 us
08:46:10.268.373.9      LastUpdate:     0.269155 s
08:46:10.999.447.0      PerfCntScale:   0.99997040      offset: 8.3 us
08:46:11.288.463.5      LastUpdate:     0.288641 s
08:46:11.999.504.2      PerfCntScale:   0.99997039      offset: -6.4 us
08:46:12.311.535.4      LastUpdate:     0.312251 s
08:46:12.999.604.2      PerfCntScale:   0.99997032      offset: 15.4 us
08:46:13.307.621.8      LastUpdate:     0.308169 s
08:46:13.999.661.4      PerfCntScale:   0.99997030      offset: -1.3 us
08:46:14.295.691.0      LastUpdate:     0.296053 s
08:46:14.999.761.4      PerfCntScale:   0.99997033      offset: 31.3 us
08:46:15.318.779.6      LastUpdate:     0.319420 s
08:46:15.999.818.6      PerfCntScale:   0.99997031      offset: 15.2 us
08:46:16.320.837.0      LastUpdate:     0.320896 s


Le 21/03/2012 00:56, Ron Frazier (NTP) a écrit :
> 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.
>



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