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How to connect my Garmin eTrex to ... On this page I briefly show you the connector possibilities for connecting your Garmin eTrex GPS receiver to a serial (RS232) based device (for example PC, Laptop, PDA). Note: Read the disclaimer! pFranc (Larry) designed his own eTrex connectors for both the rectangle shaped Garmin connector and the round Garmin connectors.

Garmin eTrex connector

Below you will find the connector pinout of the Garmin eTrex connector:

You will need this info to hook your eTrex to a PDA or PC.

The serial interafce comes in two froms, a 9-pin variant and a (older) 25-pin variant, both are connected as shown below:

eTrex Connector	Purpose		to RS232/Serieel Connector		Purpose
			9 PIN	25 PIN
pin 1	Powersupply (+ 3 Volt)		NOT used!
pin 2	RXD (Data IN)		pin 3	pin 2	TXD (Data OUT)
pin 3	TXD (Data OUT)		pin 2	pin 3	RXD (Data IN)
pin 4	GND (-)		pin 5	pin 7	GND

Note: In the RS232 column you will find two sub-columns called 9-pin and 25-pin, refering to the two RS232 connector variants. The 9-pin variant is the most common one.

Tip: If you're busy with an eTrex connector anyways then you might want to consider adding external power for the eTrex aswell. Use a 3V powersupply and connect it to pin 1 (+) and 4 (-) of eTrex connector.

The RS232 DB9 connector

This is a well known and well document connector, most of them even have numbering on the connector itself.

Below you will find tables of both variants of the serial connector.

Note: These pinouts are identical for both male and female connectors!

Note: Notice the swap op pin 2 and 3 if you compare both connectors!