[time-nuts] Inexpensive modular gps with 1pps

David J Taylor david-taylor at blueyonder.co.uk
Thu Nov 15 17:54:35 UTC 2012


From: james machado
[]
all good points David.  I originally had place mine close to a window
to get a lock as it could not acquire any satellites in my home office
otherwise.  I don't have a south facing window and my office is on the
first floor of a two story house.  That may or may not have played a
part but just placing it near the window and facing outside worked
fine.

I added the antenna (https://www.adafruit.com/products/960) and the
connector (https://www.adafruit.com/products/851)  and now I don't
have to keep my RPi and gps near the window.

What I liked about this one was it would interface with the RPi GPIO
pins without having to use a converter from RS232 to 3.3v and  I never
considered a USB gps due to the inherent issues with USB and timing.

Thanks,
James
=============================================

Well, after 5 hours the Adafruit unit finally locked - must have been just 
the right combination of satellites!  I was slightly surprised by the 
difference in antenna size.  It would have to be placed near a window for 
normal use.  Like you I have some puck antennas which I've used on other GPS 
devices, with the GPS 18 LVC being placed on the roof (it's not very 
sensitive), the GPS 18x LVC and the other units being placed indoors, some 
on a south-facing wall, but all on the top storey of a two-storey house. 
Having the extra antenna cable allows more versatility in placing the unit, 
but these are so small - even /with/ the computer, that it's a choice 
between antenna cable or Ethernet/power cable.

The 25 mm antenna NEO-6M board I got also has 3.3V interfacing which, as you 
say, is a bonus.  USB would suit as a source of coarse seconds if you needed 
a stand-alone unit for operation when out portable, although, as you will 
know, the Raspberry Pi also has a serial interface you can program for two 
of the GPIO pins, freeing up the USB ports for something else.

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk 





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