Creating the interface cable (iPaq - Etrex)

To be able to receive GPS-coordinates from the Etrex GPS in the iPaq handheld, I had to create an interface cable between the devices. On the internet I found a store on the internet which sells the seperate connectors.

I needed the iPaq 3800-series connector and the Garmin Etrex e-Type connector.

The Etrex connector		The iPaq 22-pins connector

Then I used a piece of telephone-wire for the cable between the connectors. I searched internet for the schematics of the connectors to be able to make the correct NULL-modem connection (Etrex Data Out -> iPaq Data In / Etrex Data In -> iPaq Data Out).

These are the pins on the connectors:

The Etrex connector		The iPaq 22-pins connector

Now we know the pin-numbers. Al we have to do is to connect the correct ones. In a NULL-modem wires 2 and 3 are crossed. These are the Receive Data and Send Data pins. In this case we have to connect to following wires:

In the cable I bought, were 4 wires. Black, Green, Red and Yellow.
I used Black for Ground, Red for iPaq -> Etrex and Yellow for Etrex -> iPaq.
I left the green wire useless in the cable.

When I was done, my total project looked like:

I hope this helpes someone that wants to make his/her own cable. I had a hard time finding all the needed information. Especially the pin data on the 22-pin connector of the iPaq. The information I found, was mostly for the 3600/3700 series. But eventually all of the above worked for me!!

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