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APRS with Garmin Handheld


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Hi :)

My Garmin USB to serial cable arrived today:


I’m not associated with this shop, this is just what it is, and where I got it.


The GPSMAP 64 series handheld is supposed to be supported, and I’ve tested it ok with a serial terminal program and real RS232 serial port.

I suspect 66 series will work with it as well when a USB mini to USB micro adapter (on it’s way) is used, but I've yet to actually test that.

The cable needs power for the GPS serial port to work, so there must be something active in that little moulded plastic block in the cable.


The overall plan is to have the Garmin plot received locations (any APRS beacons) on the GPS map.

Garmin specifically supported this for some Oregon and Colorado handhelds:



Also some Nuvi support this NMEA serial input, but APRS gets little if any mention after that.

I’m hoping the GPSMAP 64 and/or 66 are listening for waypoint data over the serial port as well.


Will keep updated.





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Well if someone searches this in future, I got a USB mini to micro adapter, and tested power & data connections with other devices,

and the Garmin USB serial cable didn't work with the GPSMAP66 unfortunately.

I used the same interface setting as in the menu of the GPSMAP 64, and tested various serial baud rates, but saw no signal at all.


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Back to talk to myself one more time. I got APRS tracking working with the GPSMAP 64st and Yaesu FT-2DR.

The Yaesu CT-170 data cable was used on the radio side, and the Garmin serial cable on the GPSr side.


Garmin serial cable side -----------> Yaesu CT-170 (with 2.5mm plug cut off) data cable side


Red: (+) DC Power supply for Garmin GPSr. Must be powered for serial port to work

Black: (-) DC Ground


Green ->    Cable shield (bare wire)

Yellow (serial Tx) -> Red (Serial Rx)

White (serial Rx) -> White (Serial Tx)




If you don’t want to cut the CT-170 data cable, the plug’s tip is connected to the red wire, the middle ring is connected to white,

and the ring terminal closest to the plug plastic body is connected to the bare wire sheild, which is ground.


Both devices serial ports are true RS232 level, and can interface with each other safely by direct connection.


If you find, and use this in future please drop a hello.

Cheers, VK4FAST.



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I’m guessing that’s an older one that still has a real RS232 serial port.

The 66, I found out later with help from a fellow on gpsrchive forum, does work,

but whatever USB adapter used between the 66 USB micro, and serial cable USB mini, has to connect all five USB pins as USB OTG adapters would.


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