[time-nuts] NEO-7M various modes

Thomas Petig thomas at petig.eu
Sun Oct 29 04:10:05 EDT 2017


On Sat, Oct 28, 2017 at 05:27:01PM -0700, jimlux wrote:
> On 10/28/17 3:24 PM, Wayne Holder wrote:
> > uBlox has a utility called u-center
> > <https://www.u-blox.com/en/product/u-center-windows> that's a free
> > download.  You can use it to configure the various output options (and
> > enable and disable different messages) and a then save this config back to
> > the module as the start up default.
> >
> Downloaded it, hooked up the modules, found that they won't quite get a fix
> indoors next to the window, but if I take it outside, it will. Oddly, the
> SNR on the SVs is good enough, but there's something preventing the fix from
> happening.
>
> Maybe it's because it's a cold start, it needed to run for a while to
> acquire the almanac or something.
Could be multi-path. Line of sight is blocked and the RX is receiving
reflections, that traveled a bit longer. Thus, solving the navigation
equations fails, or sometimes even worse, gives a wrong position.
Walls, windows and water surfaces provide a multi-path signal with
rather good SNR.

/Thomas, SA6CID

>
>
>
>
>
> > Wayne
> >
> > On Sat, Oct 28, 2017 at 3:12 PM, jimlux <jimlux at earthlink.net> wrote:
> >
> > > I've got 4 NEO-7M-C modules hooked up to 7 beaglebone greens, side by
> > > side, and they're not behaving the same..
> > >
> > > I've got gpsd running, and I'm looking at the output of cgps and/or
> > > gpsmon, as well as ppstest
> > >
> > >
> > > Some emit NMEA sentences, others binary (ublox?) strings?
> > >
> > > Some get a fix and start toggling the 1pps line, others don't.
> > >
> > > Is there some command string one can send to them to put them into a known
> > > state (cold reset?) - the one that's working the best (I.e. has a fix AND
> > > toggles 1pps) seems to be putting out binary strings (when viewed with
> > > gpsmon).
> > >
> > >
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