[Preston] Progress with Wireless and Linux

[Matthew T. Atkinson]

'ello,

I said I'd post about this and I've finally got 'round to it :-).  Roger
Longsworth (recently signed up) sent me a couple of WLAN cards to see if
I could make them work -- they seem to be from a duff batch.

It turns out, strangely, that they're exactly the type that we were
using at PLUG last month so I thought I'd post to tell you all how I got
on and what to do to make them work...

Given the chipset, we worked out that we needed atmel drivers.  There
are in the kernel so I'll just say how to compile them (though they were
compiled into the kernel on Guy's laptop, so we'd already got this far):

To compile them in, make menuconfig and...
Device Drivers -> Networking Support -> Wireless LAN (non-hamradio)

This is where it gets interesting, because Linux has support for /the
chip/ and then a number of interfaces that wrap it up.  It has PCI,
CardBus and USB interfaces.  To enable support for the actual chip
itself, you need to enable (module is fine) ``Atmel at76c50x chipset
802.11b support'' under ``Wireless 802.11b ISA/PCI cards support''.  DO
NOT enable the sub-option.  Instead, you'll notice a new ``Atmel
at76c502/at76c504 PCMCIA cards'' option will now be available under
``Wireless 802.11b Pcmcia/Cardbus cards support'' -- enable (or module)
that one as well.

You will also need the firmware for the device.  This is the bit we
didn't get up to in the meeting.  On Debian (Yay! Sarge is Frozen!) you
can simply do this:

$ apt-get install atmel-firmware

et voila!  When you reboot you'll get an extra network interface for the
card.  If you want to make it automatically get a DHCP address when it
is insertified, you can add the following to /etc/network/interfaces:

# wlan
auto eth2
iface eth2 inet dhcp
    #wireless_key1 <key>
    #wireless_key2 <key>
    #wireless_key3 <key>
    wireless_key <key>
    #wireless_defaultkey 4
    wireless_essid <essid>

I commented out the multi-key lines because I can't get it to work like
that.  I am also not sure of how to generate the keys from a passphrase
(which is what MacOS X seems to allow).

Summary:

Hopefully that's shown you what to do to get those cards working.
There's a lot more that I would like to do with them though, like
roaming support (we have an eduroam network here; it also authenticates
over the web like the abomination installed at UCLAN mentioned at the
last meeting but doesn't, thankfully, require ActiveX -- presumably it
adds an iptables rule that lasts as long as the DHCP lease).

You may find the program ``wavemon'' (also it's Debian package name).
It makes mistakes about the frequency on these cards but is a good
indication of how well you're doing.

The cards I have do seem to be from a duff batch; Roger mentioned the
range is not great and I would have to agree.  Looking at the SNR in
wavemon shows that it really is a bad signal.  I'm assuming 'ts the
cards as I am testing this with a friend's Linksys WRT54G -- the WLAN
router that many a Linux Distribution has been made for :-).

Still, my PowerBook has finally entered the 21st century so I am well
chuffed!  (Thanks Roger!)

If anyone has any thoughts on this, or answers to the question of
roaming (I've just not had time to look into it yet) then I'd e
interested to hear them.  I know there are ppl a lot more knowledgeable
on wireless than me here! :-).

bye just now,


-- 
Matthew T. Atkinson <matthew at agrip.org.uk>