Hardware Reference
In-Depth Information
Before you start to set up the wireless interface, you'll need to know the
Service Set Identifier
(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.
Installing Firmware
In order for the USB wireless adapter to be addressed by the system, a software bundle
known as a
firmware
is required. While some distributions include a selection of the most
common Wi-Fi firmware installed by default, others do not. Raspbian includes most com-
mon wireless firmware packages, and if this is the operating system you are using you can
skip ahead to the section on “Connecting to a Wireless Network via wpa_gui”; otherwise,
read on for instructions on installing firmware packages.
In order to download the firmware files, 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 getting online, you'll need to manually download the firmware
installation package on a different 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 flash drive.
To find the correct firmware file 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 differ-
ent manufacturers may use the same type of chip inside their USB wireless adapters, making
them all compatible with the same firmware. As a result, the labelling on a device or its pack-
aging is not enough to know which firmware you should install. Instead, you'll need to con-
nect the device to the Pi and check the
kernel ring buffer
for error messages. If you've already
connected the wireless adapter as instructed in Chapter 2, “Getting Started with the
Raspberry Pi”, you can continue. If not, connect the adapter now.
The kernel ring buffer 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
flashes 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 firmware packages installed, the kernel will print a
series of error messages to the ring buffer. To read these messages, you can use the
dmesg
com-
mand to print the contents of the buffer 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 buffer:
dmesg
