[time-nuts] Inexpensive modular gps with 1pps

David J Taylor david-taylor at blueyonder.co.uk
Thu Nov 15 15:06:10 UTC 2012


-----Original Message----- 
From: David
[]
So the 16x manual says.  As far as I know, all of the Garmin LVC, HVC,
and 5Hz versions of their receivers have a timing pulse output.

The GPS18 series that I have was replaced by the GPS18x series.

Some of their receivers have "TIA-232-F (RS-232) Compatible Polarity"
which means exactly that.  They do not provide RS-232 voltage levels
so for my GPS18-5Hz, I had to hack together a little non-inverting
level shifter (two transistors, some resistors, and a dual power
supply) to convert the 0 to 5 volts into -12 and +12 volts.
===================================================

I must have been lucky with my combination of 18, 18x and various PC serial 
port receivers, as I haven't needed a level shifter with either.  But the 
slightly less than 3V from a different 3.3V GPS does /not/ register on a 
different serial port.

Circuits:
  http://www.satsignal.eu/ntp/GPS-interface-1.png
  http://www.satsignal.eu/ntp/GPS-interface-2.png

from:
  http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm

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





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