[PLUG-TALK] USB WiFi

Keith Lofstrom keithl at kl-ic.com
Mon Oct 6 13:11:22 PDT 2008


On Sun, Oct 05, 2008 at 05:33:21PM -0700, Rich Shepard wrote:
> On Sat, 4 Oct 2008, Russell Senior wrote:
> 
> >Power varies by device.  If you are looking for a higher-powered USB
> >wifi adapter, this one looks pretty sweet and it has (not personally
> >tested) linux drivers:
> >
> > http://www.expressnets.com/sales/proddetail.asp?prod=EXPUSB200
> 
>   The ExpressNet support responded to my questions. It has a Realtek chip
> set, and the power is 23dbm. The product description page on their web site
> says that it runs with the linux 2.6 kernels, so I assume it's not as
> distribution-sensitive as is Keith's. My notebook runs Slackware, not
> Gentoo, Ubuntu, or openSuSE so we'll soon add a fourth distribution to the
> Realtek USB WiFi devices.

Ed perhaps to the contrary, there are TWO VERSIONS of the Realtek chipset.  
The B chipset only works with ndiswrapper, and bleeding-edge alpha drivers
and kernels.  The non-B chipset (which is not shipping anymore) is the one
that uses the rt73 and r8187 drivers.  I have recent direct experience with
this (Trendnet device using RTL8187B, arrived from newegg october 1 ), and
I quote from one of the rtl8187 driver developers:

From: "Hin-Tak Leung" on October 4, 2008:
> Yes, rtl8187B is in recent kernel; it is still a bit buggy but the two
> external links - cuervo's link to an old version of the vendor driver
> ported forward and there is a newer vendor driver, but neither
> supports the latest kernel - and that's not entirely bug-free either;
> there has not been much activities at the sourceforge link, so that's
> really just for reference.
> 
> I would say add these two pieces of information:
> 
> - it is known that rate-control doesn't quite work with either rtl8187
> or rtl8187b. "iwconfig rate <somerate> fixed" may work better under
> some circumstances.
> 
> - we don't support rtl8187B with a product id 0x8198 (in some very new
> toshiba laptops) yet. It seems the vendor driver works to extent, but
> report against the community driver (by adding the id) has been
> inconclusive.

Recent kernel == 2.6.27 ( see http://linuxwireless.org/en/users/Download )

If you can find older units like Ed's ( Belkin FD7050 version 4000 or
earlier) then you are good with the drivers that are probably in your
production kernel, if it is >= 2.6.18 .  Note that some of the recent
adapter USB IDs are not in earlier drivers.   

You can recompile the driver with a larger set of device IDs for more
recent products.  I just posted something to the main list about this.
In my ideal world, that list would be a user-editable file instead.

You can use a lot of different adapters if you use  ndiswrapper ,
which wraps the windows binary.  ndiswrapper allegedly works with
"wicd", the wifi control software that John Jordan likes better
than Network Manager.

Be very careful buying wifi hardware.  Many manufacturers claim Linux
compatability when they mean ndiswrapper rather than native open source
drivers.  Manufacturers also change chipsets to incompatable ones without
changing the box or the advertising blurbs.  When possible, I suggest
buying locally from Rick Lindahl at Invictus Networks, because his
prices are decent, he supports local free wireless and open source,
and he wants to learn how to support Linux as much as possible.

When the new RTL driver appears, I may attempt to backport it to my
distro (kernel 2.6.18) so I can run some of the adapters Rick sells.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs



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