[aprssig] Data cable for Garmin GPS V

Greg D. ko6th_greg at hotmail.com
Thu Mar 13 02:32:43 EDT 2008

To Earl's original questions, I believe the following should be ok:

1.  The "-" pin is also the ground for the serial connection.  It would go to pin 7 on a DB-25 female connector.  "+" is for power, of course.
2.  The "R" pin means receive into the GPS, and "T" is the GPS sending to the HUD.  I don't have a HUD myself, and long ago decided not to try to figure out which way the RS-232 transmit and receive lines go (RS-232 has had a long history of confusion on this point), but the two pins involved are 2 and 3.  I'm pretty sure pin 2 is the communications side transmit (wire it to GPS device "R"), and 3 is receive (wire to "T") - hook it up and see if it works.  If not, switch them; it shouldn't damage anything if it's backwards.  The confusion comes from the standard's perspective of hooking a device to a modem, so technically you are making a "null modem" cable in order to hook two devices together directly.

By the way, if you end up needing a female DB-9 connector instead of DB-25, the pins are 2, 3, and 5 for Tx, Rx, and Ground.  My GPS-III (same connector) is wired R to 3, T to 2, and "-" to 5, for a DB-9 female connector when connecting it directly (null modem) to a Keyspan USB serial port pod.  If you need to use male connectors, 2 & 3 will probably be swapped.

Good luck,

Greg  KO6TH

> Date: Wed, 12 Mar 2008 17:55:19 -0700
> From: scott at opentrac.org
> To: k4gps at arrl.net; aprssig at lists.tapr.org
> Subject: Re: [aprssig] Data cable for Garmin GPS V
> For an old one, the GPS V is pretty good.  In Garmin mode, at least, 
> it'll do longer waypoint names - you can see 8-character names here:
> http://n1vg.net/images/gps5-map.gif
> The symbol set is better than the older units, but there's no comment 
> text display.
> Scott
> N1VG
> Rich Garcia wrote:
>> I have never used a HamHUD but I hooked up my GPS V for the first time in
>> years this weekend when I installed my new D710 Kenwood. Funny thing
>> considering the GPS V is not the latest GPS, never thought it would do it
>> but I connected the data in to the Kenwood's GPS data out lead and after
>> setting Waypoints to 6 characters my small monochrome GPS started plotting
>> APRS stations.
>> Way too small to be usefull while driving but it was still interesting to
>> the Data in is more than for just the DGPS option.
>> Rich
>> -----Original Message-----
>> From: aprssig-bounces at lists.tapr.org
>> [mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Earl Needham
>> Sent: Wednesday, March 12, 2008 9:44 AM
>> To: aprssig at lists.tapr.org
>> Subject: [aprssig] Data cable for Garmin GPS V
>>          Looking for information on building a cable to connect my
>> Garmin GPS V to my HamHUD.
>>          The GPS V has four pins --
>>          + -- for power input
>>          - -- for power ground
>>          Data in (for DGPS receiver, etc)
>>          Data out (to TNC)
>>          It's been several years since I built one of these -- isn't
>> there a "data ground"?  And does it simply connect to the same pin as
>> the "power ground"?
>>          And -- which pin on the DB-25 is meant for data in?  Data out?
>>          Thanks,
>>          Earl
>> KD5XB -- Earl Needham
>> Clovis, New Mexico DM84jk
>> http://groups.yahoo.com/group/cw_bugs
>> Quoting from the Coast Guard: ZUT

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