bastian 22.08.2012 2 Comments

If you want to use Wifi modules such as Edimax EW-7811Un with your Raspberry Pi, you will need the appropriate driver. For unknown reasons, the kernel-included driver for this module does not work. Luckily, Realtek is providing an open-source driver for exactly this radio module. To compile it, do this:

Download the Driver

You can get it at the Realtek Homepage. The direct link is ftp://WebUser:Lc9FuH5r@209.222.7.36/cn/wlan/RTL819xCU%20_USB_linux_v3.4.3_4369.20120622.zip

Unpack and change dir

unzip RTL819xCU _USB_linux_v3.4.3_4369.20120622.zip
cd RTL8188C_8192C_USB_linux_v3.4.3_4369.20120622/driver
tar -xvzf rtl8188C_8192C_usb_linux_v3.4.3_4369.20120622.tar.gz
cd rtl8188C_8192C_usb_linux_v3.4.3_4369.20120622

Deaktivate Debug output

Open the file include/autoconf.h in your favorite editor and change the last section of the file to look like so:

/*
 * Debug  Related Config
 */
//#define CONFIG_DEBUG_RTL871X

#define DBG     0
// #define CONFIG_DEBUG_RTL819X

// #define CONFIG_PROC_DEBUG    1

//#define DBG_IO
//#define DBG_DELAY_OS
//#define DBG_MEM_ALLOC
//#define DBG_IOCTL

//#define DBG_TX
//#define DBG_XMIT_BUF
//#define DBG_TX_DROP_FRAME

//#define DBG_RX_DROP_FRAME
//#define DBG_RX_SEQ
//#define DBG_RX_SIGNAL_DISPLAY_PROCESSING
//#define DBG_RX_SIGNAL_DISPLAY_SSID_MONITORED "jeff-ap"

//#define DBG_EXPIRATION_CHK

//#define DBG_SHOW_MCUFWDL_BEFORE_51_ENABLE
//#define DBG_ROAMING_TEST

//#define DBG_HAL_INIT_PROFILING
// #define DBG_MEMORY_LEAK      1

// #define DBG_CONFIG_ERROR_DETECT
//#define DBG_CONFIG_ERROR_RESET



(in other words: deactivate everything that looks like debugging)

Build the kernel module
You will need the appropriate compiler for the module. Also, you need to have a freshly built kernel lying around. To build the driver, to this:
make ARCH=arm CROSS_COMPILE=/usr/bin/arm-linux-gnueabihf- -C PATH_TO_BUILD_SUBDIR_OF_YOUR_KERNEL M=DIRECTORY_WHERE_THE_DRIVER_LIVES modules

You end up with a file called 8192cu.ko which is your kernel module.
Install the module in your RPI

Copy the module onto your RPI
Move the module:
sudo mv 8192cu.ko /lib/modules/`uname -r`/kernel/drivers/net/wireless


Run depmod
sudo depmod -a


Prevent the stock rtl8192cu.ko module from being loaded. To do this, simply append the following line to /etc/modprobe.d/raspi-blacklist.conf :
blacklist rtl8192cu


To automatically load the newly compiled module, add the following line to /etc/modules:
8192cu


done

Standard Wifi Config
For Wifi to work, you will need two additional things.

Add the interface configuration to /etc/network/interfaces
auto wlan0
iface wlan0 inet dhcp
	wpa-driver wext
        wpa-conf /etc/wpa_supplicant.conf


Create a new file /etc/wpa_supplicant.conf with the following content:

ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=0
ap_scan=1

network={
        ssid="YOUR_SSID"
        proto=RSN
        key_mgmt=WPA-PSK
        pairwise=CCMP TKIP
        group=CCMP TKIP
        psk="YOUR_WPA_PASSPHRASE"
}

Please replace YOUR_SSID and YOUR_WPA_PASSPHRASE with the appropriate values.
Enjoy!