Hardware Reference
In-Depth Information
Before you start to set up the wireless interface, you'll need to know the
Service Set Identiier
(SSID)
—also known as the
network name
—of the wireless router to which you want to con-
nect, along with the type of encryption in use and the password required. You'll also need to
know what type of wireless network it is. A USB adapter designed for 802.11a Wi-Fi may not
connect to an 802.11g network, and vice versa.
In order for the USB wireless adapter to be addressed by the system, a software bundle
known as a
irmware
is required. While some distributions include a selection of the most
common Wi-Fi irmware installed by default, others do not. At present, to save space, most
distributions designed for the Raspberry Pi need the irmware iles for a wireless card install-
ing manually.
his, unfortunately, can lead to a Catch-22 situation: in order to download the irmware iles,
the Pi must be connected to the Internet. If you can spare a wired port on your router or
gateway for a few minutes, that's not a problem. However, if wireless is your only way of get-
ting online, you'll need to manually download the irmware installation package on a difer-
ent computer, and then transfer it across to the Pi by either copying it to the Pi's SD card or
connecting an external storage device such as a USB lash drive.
To ind the correct irmware ile to download, you'll need to know what type of wireless
adapter you have. Although various companies sell branded USB wireless adapters, the num-
ber of companies that actually manufacture the components is a lot smaller. Several difer-
ent manufacturers may use the same type of chip inside their USB wireless adapters, making
them all compatible with the same irmware. As a result, the labelling on a device or its pack-
aging is not enough to know which irmware you should install. Instead, you'll need to con-
nect the device to the Pi and check the
kernel ring bufer
for error messages. If you've already
connected the wireless adapter as instructed in Chapter 1, “Meet the Raspberry Pi”, you can
continue. If not, connect the adapter now.
he kernel ring bufer is a special portion of memory used by the Linux kernel to store its
human-readable output. It's an important part of the Linux operating system: the text
lashes by too quickly to read while the Pi boots, so it's critical that users are able to view the
messages at a later date to read errors and diagnose problems.
With the adapter connected but no wireless irmware packages installed, the kernel will print
a series of error messages to the ring bufer. To read these messages, you can use the
dmesg
command to print the contents of the bufer to the screen. At the terminal, or at the console
if you haven't loaded the desktop environment, simply type the following command to view
the bufer:
dmesg
