Category list

Chapter 1. Bluetooth, Mobile Phones, and GPS

1.1. Hacks 122: Introduction

There is much talk in the communications industry of providing last-mile connectivity. Think of Bluetooth as providing connectivity for the last 10 feet. Bluetooth excels as a handy cable-replacement technology, helping to eliminate the need for cumbersome wires that you might find on headsets, remote controls, PDAs, and other small devices. Bluetooth aims to end the days of needing to carry a three- foot piece of cable with obscure connectors on either end everywhere you go, just to interface to your laptop. You can use Bluetooth-enabled devices to talk to a laptop or a desktop, or even have them talk to each other to exchange data almost effortlessly. This chapter presents hacks on getting Bluetooth working with a wide range of devices and then doing some very interesting tricks.

If you can provide connectivity for the last 10 feet, how do you find yourself on this blue-green sphere we call Earth? The global positioning system (GPS) has migrated from being a military-only technology to something that is built into cars , phones, and a number of other devices. In this chapter, you can learn how to do some very unusual things with GPS that the designers probably never intended.

Mobile phones are everywhere. For many people, they have become the sole telephone of choice, enabling them to abandon land lines altogether. When you combine a mobile phone and Bluetooth, even more hacks become possible.

Hack 1. Set Up Bluetooth on Linux

Linux kernels from 2.6 onward have easy-to-use tools for Bluetooth .

Prior to the release of the 2.6 Linux kernel, getting Bluetooth support involved compiling your own kernel as well as the necessary utilities. There were also multiple Bluetooth stacks available, each with their own features, adapter support, and quirks . In 2.6, the BlueZ stack was crowned as the officially supported way to use Bluetooth in Linux, and that's the focus of this hack.

First, make sure you have a supported Bluetooth adapter. You used to be able to find a reasonably current list of BlueZ-supported hardware at http://www.holtmann.org/linux/bluetooth/devices.html. However, as of March 2005, this information has been removed because of threatened legal action from the Bluetooth SIG. What this basically means is that the association of companies who maintain the Bluetooth standard don't want anyone to advertise that their devices are compliant with Linux unless you pay the SIG a lot of money and fill out a bunch of paperwork. So, you're on your own here. Probably the best place to get advice is in the BlueZ Users mailing list, which can be found at http://www.bluez.org/lists.html.

Next , you'll need to make sure that your kernel has Bluetooth support enabled. All distributions shipping the 2.6 kernel have Bluetooth support. 2. 4 kernels shipped with both the Red Hat 9.0 and Debian Sarge distributions already include Bluetooth support. You can test your kernel for Bluetooth support by running modprobe rfcomm as root. If the modprobe fails, you'll need to install the packages that support Bluetooth.

Red Hat and Fedora users should install these packages using yum or rpm . This assumes you're using GNOME as your window manager:

yum install bluez-utils gnome-bluetooth

Likewise, Debian and Ubuntu users should install using apt :

apt-get install bluez-utils gnome-bluetooth

This next bit is for UART-based (that is, non-USB) devices only, so if you're using a USB Bluetooth adapter, you can skip ahead. Serial-style USB devices, which include serial dongles and PCMCIA cards, need to be explicitly attached to the Bluetooth host controller interface, using the hciattach utility. When you connect the device, the appropriate kernel driver might be loaded automatically, leaving a log entry in /var/log/messages .

If you're using a UART-based device, you may see a reference to a /dev/ttySn serial device, where n is some integer. In any event, you can try attaching the device to the Bluetooth host controller device by running /sbin/hciattach/dev/ttySn any from the command line. Like any good Unix utility, you know that hciattach worked if it returns without printing anything. If it doesn't work, make sure you have the right device and check the manpage for other options.

Assuming that the hciattach command did work, you will want to add a reference to this device to your /etc/bluetooth/uart file, so that the device can be appropriately attached to the Bluetooth host controller interface at boot time. If this file doesn't exist, create it. Add a single line to this file that reads /dev/ttySn any , replacing n with the appropriate serial device number.

Now that you have everything installed, plug in your Bluetooth adapter and try running /etc/init.d/bluetooth start as root. In Debian and Ubuntu, start Bluetooth with /etc/init.d/bluez-utils start . You should see some appropriate status messages in your /var/log/messages . Assuming everything works, you might want to add the Bluetooth script to the appropriate rc.d directory for your default run level with the chkconfig utility or via a manual symlink . Chances are good your package install has already added this for you, but it's a good idea to check.

Now run hciconfig from the command line. You should see something like

hci0:	Type: USB
			BD Address: 00:11:22:33:44:55 ACL MTU: 192:8 SCO MTU: 64:8
			UP RUNNING PSCAN ISCAN
			RX bytes:99 acl:0 sco:0 events:13 errors:0
			TX bytes:296 acl:0 sco:0 commands:12 errors:0

If you don't see anything like this, make sure that hcid is running and that there aren't any error messages in /var/log/messages . The BD Address shown is the unique Bluetooth identifier for your adapter, much like an Ethernet MAC address.

Now, bring another Bluetooth device within range of your computer, and make sure that the device is visible to Bluetooth scans . Then, run hcitool scan from the command line. It might take up to 15 or 20 seconds to complete its scan, and then it should display something like this:

$ hcitool scan

	Scanning …
			00:99:88:77:66:55	Nokia3650

You can now test the device to see which services it supports, using sdptool browse 00:99:88:77:66:55 . You should see a lengthy list of supported services, providing information that can be used to configure access to those services.

Schuyler Erle

Buy on amazon.com >>

Flickenger R., Weeks R.

<< Previous page

Table of contents

Next page >>