[ntp:questions] Consumer GPS question

Terje Mathisen terje.mathisen at hda.hydro.com
Tue Feb 6 22:08:32 UTC 2007

shane-dated-1173382499.fffb68 at cm.nu wrote:
> Hey all,
> I am looking at the possibility of using a GPS receiver for NTP time sync
> either via the nmea refclock driver or gpsd, just a little home project. 
> From my googling, I've read that the only way to get decent results is to go
> with an rs232 sync and stay clear of usb or bluetooth.  Looking at the
> mainstream gps sites, I've found the Globalsat br-355 unit and I'm wondering
> whether this is suitable for NTP sync and what kind of accuracy I should
> expect.
> http://www.buygpsnow.com/globalsat-br-355-water-proof-serial-gps-receiver-sirf-star-iii-br355-v3-1-1-free-arkon-mount-432.aspx
> The device seems to use a ps2 cable which converts via a y-cable into a db9
> serial connection and gets power from the PS2.  What I can't seem to find in
> the specs or on the globalsat site is whether the db9 connection provides a
> PPS output.  If not, are there any PPS capable receivers out there that
> don't require electronics knowhow (soldering etc.)?  That's all I've found
> so far.

By far the easiest/cheapest is the Garmin GPS-18 VLC (??? model ???), 
i.e. the one that comes with naked rs232 wires.

If soldering is really anathema to you, then you can buy an rs232 plug 
with screw connections for all the wires, use this connector to attach 
the red&black wires from a stripped USB cable for power.

We've documented this setup in the ntp wiki afair.


- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"

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