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I've recently bought a SheevaPlug low power computer and a Realtek RTL8188SU Wireless N USB adapter.

The SheevaPlug is unlike regular PCs based on the i386, it is actually an ARM platform. With Ubuntu no longer supporting ARM platforms, I've decided to try to use Debian. After installing Debian, I soon realised that the Realtek isn't supported.

Using lsusb, my Wireless USB adapter is identified as:

Bus 001 Device 003: ID 0bda:8171 Realtek Semiconductor Corp. RTL8188SU 802.11n WLAN Adapter

According to the Debian Wiki, the RTL8188 uses the r8192s_usb driver, however it is currently only supported on i386 and amd64. Having no luck compiling the source code that came with the usb adapter, I ventured on to IRC for the first time, and with the help of JimdiGriz at #debian-arm, I was able to get it to work fully now, it requires compiling a custom kernel. Below is the steps that I've followed in order to get it all to work.

On a Debian Squeeze machine (I've had it installed on a VirtualBox virtual machine), if you have lenny, make sure you do a dist-upgrade to squeeze first. Then add emdebian.org to the repository by running:

deb http://www.emdebian.org/debian/ lenny main' > /etc/apt/sources.list.d/emdebian.list

Then update the repository

apt-get update 

install the following packages:

apt-get install build-essential gcc-4.3-arm-linux-gnueabi libc6-dev-armel-cross libc6-armel-cross kernel-package fakeroot

Now, download the source code for the linux kernel from Debian Repository without installing it. Then extract the package to a temporary folder, in this case, /usr/src/moo

dpkg -x linux-source-2.6.32_2.6.32-20_all.deb /usr/src/moo

Now, extract the source code:

cd /usr/src; tar jxf /usr/src/moo/usr/src/linux-source-2.6.32.tar.bz2

Now, we need to download the kernel configuration file and save it as .config in the /usr/src/linux-source-2.6.32 folder. A copy of the configuration file can be found at Sheeva.with-linux.com

Create an alias by running

alias amake="ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- make"

Now, we need to add support for the wireless usb adapter using the menuconfig by running:

amake menuconfig

Select Device Drivers, Staging Drivers, RealTek RTL8192SU Wireless LAN NIC driver, (check the Debian wiki to see which RealTek driver you need based on your lsusb output) and press [M] to modulise it, now Exit the menuconfig program and save the configuration.

Now, you are ready to compile the kernel driver.

make-kpkg --initrd --arch armel --subarch kirkwood --cross-compile /usr/bin/arm-linux-gnueabi- --revision=0 --append-to-version=-custom --rootcmd fakeroot kernel_image

After a long time, it will finish compiling. You will find a deb package created in /usr/src/, the name of it should be  linux-image-2.6.32-custom_0_armel.deb. Copy the deb package to the SheevaPlug. The easiest way is to have openssh-server installed on the SheevaPlug, and then you can scp the file over.

On the SheevaPlug, install the deb package by running

dpkg -i linux-image-2.6.32-custom_0_armel.deb

Now, you need to create a uImage file. In order to create this, you will need to install the following packages on the SheevaPlug:

apt-get install mtd-utils uboot-mkimage 

Create a backup of /boot/uImage, then create the new uImage by running

mkimage -A arm -O linux -T kernel -C none -n uImage -a 0x00008000 -e 0x00008000 -d /boot/vmlinuz /boot/uImage

If your kernel is on the internal flash, you should run the following as well to copy it to the flash:

flash_eraseall /dev/mtd1
nandwrite -p /dev/mtd1 /boot/uImage

Now, reboot and you should see your wireless usb adapter kick into action. In order to use it, you will need to configure it. The following is adopted from the Debian Wifi Wiki.

If you are using WPA security, install wpasupplicants

apt-get install wireless-tools wpasupplicant firmware-realtek

Change the permission of /etc/network/interfaces to 0600

chmod 0600 /etc/network/interfaces  

In your favourite text editor, add the following to your /etc/network/interfaces:

auto wlan0
iface wlan0 inet dhcp
wpa-ssid mynetworkname
wpa-psk mysecretpassphrase

Now, restart networking (or just reboot the SheevaPlug) and you should be able to use the wireless usb adapter on the SheevaPlug.

Many thanks to JimdiGriz at #debian-arm for his patience in guiding me through the cross compilation process, and the authors of the following pages for the help they provided as well.

• Compiling Linux Kernel: http://www.digriz.org.uk/debian-kernel-compile
• Updating the Kernel: http://www.digriz.org.uk/kirkwood#UpdatingtheKernel
• Installing Debian to SheevaPlug: http://www.plugcomputer.org/plugwiki/index.php/Installing_Debian_To_Flash
• Using rtl819x on Debian: http://wiki.debian.org/rtl819x
• Configuring WiFi: http://wiki.debian.org/WiFi/HowToUse

For those who couldn't get it working, I've included the deb package.