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Connection Types

There are three main ways to connect a GPS to a PC: serial (COM) port, USB, and wireless (Bluetooth). The following sections describe each of these connection methods.

You can also get GPS receivers that connect to the Compact Flash/PCMCIA slots on PCs and PDAs. An example of this kind of receiver is the Haicom HI-401 shown in Figure 7-2. However, each of these devices uses proprietary software and they differ a great deal from one another. If you have one of these, consult the manual.

Serial (COM) Port

The 9-pin serial port (shown in Figure 7-4) is the main way that most people connect their GPS to a PC.

Several reasons account for the popularity of the serial port:

Most PCs, except for some of the newer ones, such as laptops, have at least one serial port to which devices (such as mice and modems) can be connected. Years ago, these ports were in great demand, and you often had to disconnect a device in order to connect a new device. Now that fewer devices need a COM port (because USB ports have superseded them), they are less in demand, and most people have the cable permanently connected to the port.

Adding serial port support to a device is cheap, and so well established that there are rarely problems associated with it (if configured to the appropriate speed and the software is looking for the GPS on the right port).

The data transfer to and from the GPS device does not need to be a high-speed connection, so a serial connection is ideal.

There is another hidden benefit of using a serial port connection over, say, USB. Take a look at the connector. The two thumbscrews used to hold the connector to the port secure the connection, which is usually more secure than a USB connection because of these, and they are usually more compact — USB cable connectors can extend for some distance from the port and can be more prone to damage from being knocked around than a serial port connector.

If you don’t have a serial port on your system but you still want to use a serial cable, there are ways around this issue:

Install more serial ports. Several serial port expansion cards on the market enable you to add more (or new) serial ports to your PC. This solution will work for desktop PCs that can accept expansion cards, but not with laptops.

For systems that cannot take expansion cards, for whatever reason, you can add a USB- to-serial converter. Most of these enable you to create a new serial port on a USB port that you can connect the GPS cable to. pFranc makes one such converter, which you can see at http://pfranc.com/usb/usb.mhtml.

USB

Serial ports have slowly been replaced by the faster, more versatile, and less hassle USB (Universal Serial Bus) port (see Figure 7-5).

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FIGURE 7-4: A PC serial port

FIGURE 7-5: USB ports on a laptop

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A USB port can support data transfer at 12 Mbps (megabits per second), whereas serial ports can manage only 115.2 Kbps (kilobits per second). Another advantage of USB over the serial port is that it breaks the “one port, one device” rule that was pretty much absolute with a serial port. A USB port can support up to 127 devices daisy-chained to a single port.

While the USB port has gained a lot of popularity and most computers sold today have two, if not four, ports per machine, GPS manufacturers haven’t been as speedy in jumping on the bandwagon. Some manufacturers (such as Garmin) make USB cables for some, but not all, of their handheld units.

Bluetooth

Wires are fine for connecting devices together, but they lack cool. For the ultimate in cool and convenience, what you need is a wireless connection. Bluetooth is a great way to achieve this. Bluetooth is a wireless communication technology that can be found on many PCs, PDAs, and cell phones. It offers many advantages over a standard wired connection:

Greater distance: You can place the GPS device farther from your PC than you can with a standard wired connection (most COM cables are under a meter long).

Less tangle: Cables nearly always mean tangles. Wireless connections eliminate cables and thus eliminate tangles.

Reduce the risk of damage: Tangled cables can place stress on connectors that can damage the cable or the device. Wireless eliminates this problem.

Send the signal through walls: If you have a GPS on a boat, for example, you might have the GPS outside and the PC inside. A wireless connection eliminates the need for holes in the wall for cables. It also makes it easier to move your GPS and PC without having to reroute cables.

Easier to connect: If connections mean cables, you can find yourself needing different cables for different GPS units and PCs/handheld devices. A wireless connection eliminates this, making the process of setting up connections easier.

The only problem with wireless connections is that you need a GPS that is specifically designed for Bluetooth — it’s not something you can bolt onto any GPS. GPS Bluetooth units are normally a receiver only. Figure 7-6 shows a Haicom Compact Flash GPS along with a Bluetooth “slipper” that it can be attached to, enabling the data to be transmitted to any Bluetooth receiver.

Once you have a Bluetooth device, you need a Bluetooth receiver. These are available in a variety of styles. Some devices, such as the HP iPAQ 5545 (shown in Figure 7-7), already have built-in support for Bluetooth.

PCs that don’t have support for Bluetooth can have support added with a USB Bluetooth dongle, such as the one shown in Figure 7-8.

These dongles plug into a spare USB port. You install the drivers and there you have it — Bluetooth support on pretty much any PC.

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FIGURE 7-6: Haicom Bluetooth GPS setup

FIGURE 7-7: The iPAQ 5545

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FIGURE 7-8: USB Bluetooth dongle for PCs

The range over which Bluetooth devices can work varies dramatically. The maximum range for most Bluetooth devices is 100 meters, but some have only the power to operate over distances as short as 10 meters. These are the maximum distances under ideal conditions, but several factors can dramatically reduce the range:

Partitions: Walls and car and boat skins can all have an adverse effect on the range. The denser and thicker the partition, the worse the effect.

Trees/vegetation: Both of these can have an adverse effect on the communication range. Tree trunks are particularly bad for the signal because they are filled with moisture, which absorbs the signal.

Electronic interference: Interference from other electronic devices, and even wiring, can have an unfavorable effect on distances over which devices communicate.

Power consumption: If your devices have a low-power mode, this can dramatically cut the distance over which your devices can exchange data. For the best performance, make sure low-power mode is disabled.

Bluetooth devices are in fact divided into three classes:

Class 1 has a maximum power output of +20 dBm and a range of up to 100 meters.

Class 2 has a maximum power output of +4 dBm and a range of up to 20 meters.

Class 3 has a maximum power output of +0 dBm and a range of up to 10 meters.