[time-nuts] GPS for ntp

Neil Schroeder gigneil at gmail.com
Mon Oct 20 22:50:46 EDT 2014


The one thing that hasn't yet happened is making the beaglebone timestamp
on the linux side in a way that works for ntp.

Custom code no problem. Freebsd PPSAPI no problem. Linux, nothing there
yet.

I have been working on it but if anyone has some insight its appreciated.

On Monday, October 20, 2014, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> There is a *lot* of detail on this in the archives.
>
> Quick rundown - the Soekris has some custom code and “stuff” that makes it
> better for NTP than any of the other boards.
>
> For any normal use, a couple of microseconds is likely “good enough. For
> that, many boards and GPS’s will do just fine. Yes people have gotten NTP
> running on just about every board that will run Linux.
>
> Bob
>
> > On Oct 20, 2014, at 9:39 PM, Joseph Gray <jgray at zianet.com
> <javascript:;>> wrote:
> >
> > What does everyone think of this GPS module for ntp use? According to the
> > specsheet, it uses a Ublox Neo-7N.
> >
> >
> http://www.ebay.com/itm/RY725AI-10Hz-UART-USB-interface-GPS-Glonass-QZSS-antenna-module-flash-memory-/181562403752
> >
> > I'm thinking about using it for a Beaglebone ntp server. I know there was
> > some discussion about Beaglebones a while back. Has anyone gotten ntpd
> with
> > PPS and time stamping running on a Beaglebone yet (like on the Soekris
> > Net4501)?
> >
> > Does anyone want to take a wild guess as to the best/worst case UTC
> offset
> > I might get with such a setup? I realize that I'd have to try it to
> really
> > find out, but guesses and advice from those more knowledgeable is always
> > appreciated.
> >
> > What I'm really after is to eventually have several Beaglebones scattered
> > around the area as part of a TDOA DF network. I have spare radios to
> > dedicate to the task. Each fixed node will timestamp incoming
> transmissions
> > and then relay that information to a central location. The central system
> > will use the data to calculate the location of the transmitter.
> >
> > Does anyone here have any experience with this sort of thing? Would you
> > recommend a better way of accurately timing the transmissions vs using
> ntp
> > on each Beaglebone?
> >
> > I know that TDOA is used by the cellular companies. Is anyone aware of
> some
> > "user level" projects or source code for this? I've Googled a bit, but
> > haven't turned up much. There was one thesis about an Amateur doing part
> of
> > this, but he didn't have much detail on the satellite nodes and didn't
> > describe anything about the centralized processing part.
> >
> > I have one Beaglebone White that I got cheap, so I have something to get
> > started with. Later, as I figure out things, I'll buy a few Beaglebone
> > Blacks.
> >
> > Joe Gray
> > W5JG
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