[ntp:questions] Re: Garmin gps18: The best DIY gps refclock?

Roman Mäder newsXXF.10.rmaeder at spamgourmet.com
Mon Nov 28 14:22:44 UTC 2005

Eugen COCA wrote:

> I was interested about how did you connect the PPS signal to the RS232
> interface, say the wardware configuration.

I simply connected the PPS wire (yellow) to the DCD (carrier detect) of the
same serial port that receives the data from the Garmin. You have to create
a link /dev/pps0 -> /dev/term/b, because the PPS refclock (#22) looks there
for the PPS signal.

the connections go like this:

Garmin                  RJ45                    DB25f-Adaptor   Sun DB 25

Vin     Red             7,5     ws/br,ws/bl     gn,br           (+5V)
Gnd     Black           8,1     br,ws/or        bl,ws           (Gnd)

PPS     yellow          2       or              or       8      DCD (PPS)
Gnd     black           4       bl              rt       7      Gnd
Tx      white           3       ws/gn           sw       3      Rx (in)
Rx      green           6       gn              ge       2      Tx (out)

(color codes:
ws=white, sw=black, br=brown, bl=blue, or=orange, gn=green, ge=yellow,

the power lines are not connected to the DB25, but to an external power
supply. The RJ45-DB25 adaptor is item 12.03.8030 from rotronic,

For setting up the Garmin, the DB25 is conntected via an adaptor to the DB9
port of a laptop running Garmin's SNSRCFG tool. This is also how I updated
the firmware.

Roman Maeder

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