How to Set up the Edimax EW-7811Un USB WiFi Adapter on Your Raspberry Pi

Before booting up the Pi, plug in the USB WiFi adapter as well as the ethernet cable.

To boot the Pi, simply plug in the power cable.

By default, the raspberry pi uses the hostname "raspberrypi". So you can SSH using:

ssh pi@raspberrypi

The default username is pi, and the default password is raspberry. Refer to this guide for more information on the default username and password..

If you're having trouble with the hostname, follow this guide to find the IP address of your Raspberry Pi.

Once you're logged in to the Pi, check to see if the Pi recognizes the USB device using the following command:

lsusb

You should see the following:

Bus 001 Device 004: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter
Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp.
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

Notice the first line.

Now we'll check to see if the device drivers are loaded. To list the kernal modules use:

lsmod

You should see something like:

Module                                   Size              Used by
cfg80211
rfkill
8192cu       
bcm2835_gpiomem
...

8192cu is what we're looking for, and it looks like it's installed.

As a final check, run:

iwconfig

And you should see the wireless adapter here:

wlan0     unassociated  Nickname:"<WIFI@REALTEK>"
          Mode:Managed  Frequency:2.462 GHz  Access Point: 20:3D:66:44:C6:70
          Bit Rate:72.2 Mb/s   Sensitivity:0/0
          Retry:off   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=100/100  Signal level=100/100  Noise level=0/100
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

Now, open the following file to add our network credentials.

sudo vim /etc/wpa_supplicant/wpa_supplicant.conf

Add the following to the end of this file:

For Raspbian Jessie:

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

For Raspbian Stretch:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
network={
    ssid="SSID"
    proto=RSN
    key_mgmt=WPA-PSK
    pairwise=CCMP TKIP
    group=CCMP TKIP
    psk="PASSWORD"
}

Of course, you'll need to substitute your SSID and password.

Remove the ethernet cable, and reboot with the following command:

reboot

Now you should be able to connect over WiFi.