Re: [gpsd-users] Enable PPS Echo

[Reto Zbinden ST]

Hello Hans

Thanks for this very interesting article. Therefore we might assume, that the 
PPS processing is quite accurate (even on a slow ALIX box) and delay is mainly 
introduced by the internet connection. It's an asymmetrical cable link with 200 
/ 20 MBit/s and the average round-trip-time to the NTP is about 9 ms.

Mainly because of my personal interest, I thought it would be interesting to do 
some (simple) measurements and to learn more about the processing time of the 
hardware I'm using. Maybe it's easier to take the box to my workplace and 
compare it to the Meinberg NTP which we're running on the LAN. 

Regards
Reto

-----Ursprüngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von hans mayer
Gesendet: Dienstag, 5. April 2016 22:51
An: address@hidden
Betreff: Re: [gpsd-users] Enable PPS Echo



Dear Reto,

How is your Internet connectivity ?
Is it maybe ADSL ?
If so look here:  http://blog.mayer.tv/2016/03/16/ntp-and-adsl.html

Kind regards
Hans



Am 05.04.2016 18:17, schrieb Reto Zbinden ST:
> Dear all
>
> I'm not really sure if this is the right place for my question, but maybe 
> somebody may help me:
>
> I'm running Debian with gpsd and ntpd on an older ALIX board as the time 
> source for my local network. This setup is working well for quite some time 
> and the clock is kept to within a few microseconds of the 1PPS reference.
>
> But if the time is compared to some reliable public stratum 1 servers (e.g. 
> metas.ch), it seems that the local clock is always a few milliseconds behind 
> these servers. I'd like to do some more precise measurement to figure out the 
> latency of the 1PPS signal processing and to adjust the fudge time. According 
> to what I've read, the delay can be measured using an oscilloscope and the 
> PPS echo feature. But I couldn't figure out how the echo function can be 
> activated.
>
> Can anyone provide some guidance on how to enable the PPS echo function? Or 
> maybe there's another way to do some measurements? Many thanks for your help.
>
> Regards
> Reto
>
>