Chapter 2 — Building GPS Data Cables and Power Cords

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FIGURE 2-23: Label cables clearly to avoid confusion.

GPS/iPAQ Connections

Without a doubt, one of the most common GPS-to-device connections after the GPS-to-PC connection is the GPS-to-iPAQ connection. The iPAQ is a versatile companion to a GPS that, with the right software, enables you to do all sorts of things, from plotting your position on maps to planning and navigating a car journey.

The easiest way to connect a GPS to an iPAQ is using an appropriate cable that you can buy from the manufacturer. However, another great way to get a connection is to modify an iPAQ cradle to enable you to get a connection via the cradle.

A good source of cables is http://pc-mobile.net/gps.htm.

You could make the connection via the 9-pin D connector on the cradle (using the pins detailed earlier), but it’s much more elegant if you make the connection an internal connection.

34 Part I — Hardware Hacks

Cradle Modification

Here’s how you carry out the cradle modification:

1.First, find your cradle! Once you’ve found the cradle, you need to open it. It’s not held together with normal screws but with Torx screws. You will need a Torx bit or size T6 screwdriver (see Figure 2-24) to get inside the cradle. Don’t try to use anything else or you will surely strip the screw heads.

FIGURE 2-24: T6 Torx bit

2.Unplug the cradle from the PC. Undo the screws (see Figure 2-25) and be sure to keep them safe.

3.Once all four of the screws are out, start taking the plastic parts apart. This should be quite easy to do and requires no real force or pressure. Make a note of how it all comes apart for reassembly and be sure not to lose any of the springs.

Chapter 2 — Building GPS Data Cables and Power Cords

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FIGURE 2-25: You need to undo these screws.

4.The bit inside that you are interested in is the little circuit board that plugs directly into the iPAQ serial port when it rests in the cradle. This is the green board with the black socket and USB cable connected to it.

5.Carefully free the board from the slot in the cradle so you can work on it (see Figure 2-26). Be very careful when you are handling it because the USB cable wires can easily break off of the board. If they do break, it’s not the end of the world — you can easily solder the connections if it happens; but as always, it’s better to avoid it.

6.You now need a cable with a GPS connector on one end. On this, three wires are of interest to you — from pin 2, pin 3, and pin 4. The goal is to solder these three wires to the appropriate pin on the cradle. At first, there may seem to be a lot of pins, but you will be relieved to know that only twelve are used, the rest being frame grounds.

7.The two pins that are of interest to us are pins 7 and 8, as shown in Figure 2-27. Pin 7 in the cradle needs to be connected to the wire from pin 2 on the Garmin eTrex connector, while pin 8 should be connected to the wire connected to pin 3. The easiest way to do this is by soldering the wire, but because the pins are so small and fragile, you do need to take care. It may test your soldering skills to get it right!

36 Part I — Hardware Hacks

FIGURE 2-26: Carefully remove the circuit board from the cradle.

Pin 7

Pin 8

FIGURE 2-27: Pins 7 and 8 on the board.