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Northern Illinois APRS Network Home discussion group for NIAN
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kc9aer
Joined: 25 May 2006 Posts: 2
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Posted: Thu May 25, 2006 4:53 pm Post subject: KAM 98 and eTrex interfacing
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I am having trouble trying to interface my Garmin eTrex Legend with the AUX port on my KAM 98. I put a gender-changer on the end of the PC cable so it would connect the two devices together but it didnt seem to work. Is there something I am overlooking?
Im fairly new to the GPS interfacing. |
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ka9vnv Site Admin
Joined: 08 Jun 2004 Posts: 152 Location: Woodstock, IL
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kc9aer
Joined: 25 May 2006 Posts: 2
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Posted: Sun May 28, 2006 12:30 pm Post subject:
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Thanks for the link to that KB article as it helped out a lot! All I did was buy the null modem adapter and a F-F gender changer and it worked. However, I cannot get it to work with the AUX (GPS port) port and it doesnt appear to work on that port. Do I have to do something special to get it to work on there? |
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ka9vnv Site Admin
Joined: 08 Jun 2004 Posts: 152 Location: Woodstock, IL
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Posted: Mon May 29, 2006 2:34 am Post subject:
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You need enable the GPS port, as well as make a proper interface cable...
Quoting from the former plustracker file from the Questionable web page (removed because it contained obsolete information):
Quote: | First, you need a cable to attach the GPS. The second port is part of the Radio Port wiring, and it may be easiest to start a new cable, depending upon how "creative" your current cable is. I'm only going to deal with the second serial port here - the radio connection is just like the manual shows, no changes.
You will need 2 DB-9 male connectors (one ships with the TNC, Radio Shack 276-1537 works fine, though), a short piece of 2-wire cable for the serial port, and whatever other cable and connectors are needed for your radio. Oh, I guess a couple of DB-9 hoods (Radio Shack 276-1508, -1539 or -1513, depending upon your preferences) would be nice to make things neat, and to take the stress off the solder joints.
Alternative! Don't feel like building your own cable? Already have a Kantronics TNC-to-radio cable, and don't feel like modifying it? Check out Guy Story KC5GOI's offer to build splitter cables for the soldering-impaired...
Pin 2 on the TNC is the Data IN line, Pin 6 is GROUND for all signals. This is darned convenient, because Pin 2 on a standard 9-pin serial connector is where the external device is trying to stuff its data... although the signal ground is on Pin 5. This is called "DTE wiring", in that the in/out pins of this connector are arranged the way they are on data terminal equipment, rather than "modem wiring", like is found on the TNC's main serial port.
[ You might ask, "why chose a DB-9 male connector, wired DTE?" I chose this because you can then use the same cable you use to connect the GPS or other device to your computer to connect it to the TNC's second port. ]
So, you are adding a two-wire cable between pins 2 and 6 of the TNC's Radio Port and pins 2 and 5 of the new serial connector. After this is soldered together, assemble the hoods over the connectors to protect them. |
That takes care of the hardware end, then you set:
Code: | INTFACE TERMINAL
GPSPORT 4800 NORMAL CHECKSUM
LGETCHAR $05 |
Which converts back to using the computer port for the computer, and turning on the GPS port at 4800 baud. The final command makes the TNC respond to the "APRS Standard" Ctrl-E position enquire command. |
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