Data Hacking

150 Part II — Software Hacks
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Now that fewer devices need a COM port (because USB ports have superseded them), they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 USBto-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).