[ntp:questions] Shared PPS source/Multiple PPS sources

William Unruh unruh at invalid.ca
Fri Feb 6 21:37:37 UTC 2015


On 2015-02-06, walter.preuninger at gmail.com <walter.preuninger at gmail.com> wrote:
> Ok, so these questions might be off the wall.
>
> Is there any reason why I could not share the PPS output of say, my u-blox 7 GPS module on multiple computers? Would it be good or bad to peer these 2 systems with each other?

By share you mean run the PPS output to each of the computers? The main
thing you would need to do is make sure that the gps is able to handle
the current load, and that the signals had the appropriate level at each
of the computers. 


>
> On the opposite end of the spectrum, would it be reasonable to have a PPS output from said module on a computer, with a second PPS (from another GPS module) on that same computer?

Sure. you need to have two differnt interrupt lines available (GPIO,
serial ports, parallel ports)

>
> The Chronodot/DS323X chips have 1 Hz sqaure wave output and they have +/- 2ppm. It seems that the ATOM clock driver could be used, but would it be better to write a driver specifically for this chip?

2PPM is not that great. That is one second out per 6 day. A minute out
per year. 
What is that chip. 

. 
>
> And a side question: Is it the GPS module that calculates when the PPS goes active? Is this signal compensated for the time it takes the signal from the sats in the module, or on the SV?
>

No idea what an SV is. But yes, it is compensated for the time from the
sattelite to the receiver. That is why to determine time, the receiver
needs to know where it is on the earth. It is not compensated for the
time from the gps receiver to anywhere else. 


> Does someone know the admin of tick.uh.edu? I am not getting a response from them or the server.

What reponse do you want? Why should they respond to you?
>
> Thanks
>
>
> Walter



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