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Alright, I have been unable to find a solution to this problem anywhere else online, so please bear with me:

I have a new Raspberry Pi Model 2B which came with a wifi dongle (Ralink RT5370) and when I fired it up with the pre-installed Raspbian, the wifi worked correctly. I also bought a mini HDMI screen for the pi which wouldn't work without installing the driver from a DVD shipped with the screen. After installing the driver, the screen works well, but now my wifi stopped working. The light on the dongle does not turn on anymore and I am unable to scan for wireless networks.

After some searching on Google, I have determined that the dongle is recognized (it is listed when I run lsusb), its module is installed (the module rt2800usb is listed when I run lsmod), and the firmware seems to be installed (I ran ifconfig -a and it displays wlan0 information). However, when I run iwlist wlan0 scan, I get the output:

wlan0    Failed to read scan data: Network is down

And when I run sudo ifdown wlan0 && sudo ifup wlan0 to see if the network is reachable, I get the following output:

ifdown: interface wlan0 not configured
wpa_supplicant: /sbin/wpa_supplicant daemon failed to start
run-parts: /etc/network/if-pre-up.d/wpa_supplicant exited with return code 1
Failed to bring up wlan0

I have tried editing both /etc/network/interfaces and /etc/wpa_supplicant/wpa_supplicant.conf according to various examples online to no avail. Here are my current versions:

interfaces:

auto lo
allow-hotplug lo
iface lo inet loopback

allow-hotplug eth0
auto eth0
iface eth0 inet manual

allow-hotplug wlan0
auto wlan0
iface wlan0 inet dhcp
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

wpa_supplicant.conf:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="mySSID"
    key_mgmt=WPA_PSK
    proto=WPA
    pairwise=TKIP
    psk="myPassKey"
}

As a side note, I have triple-checked that my network information is correct and that the wifi network is discoverable from other computers, so I doubt that the problem is on that end. I am at a point where I really have no idea where or what my problem could be. I have tried downloading wifi managers, that didn't work. I have rebooted, updated, and upgraded my software versions repeatedly, that didn't work. I have tried altering and/or removing lines from the above files, that didn't work. I consistently am unable to scan for wireless networks (Note: ethernet works fine) despite successfully connecting to networks before installing this screen driver! If anyone has any idea what my problem might be and how to fix it, I would be extremely grateful. Thanks!

Kyle
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8 Answers8

7

One of the things that I have read a hundred times in dealing with anything attached to the USB on any model of RPi is to make sure that you have a decent Power Supply (2 or more Amps) or use a quality powered USB hub. Could it be possible that your WiFi dongle isn't getting enough power now because the HDMI screen is too greedy?

SlySven
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David Bumpus
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2

just in case it might help. I was following this tutorial https://www.sunfounder.com/wiki/index.php?title=How_to_Use_an_RFID_RC522_on_Raspberry_Pi

Basically, after editing the sudo nano /boot/config.txt file and setting device_tree=on

broke my wireless on the next reboot. Deleting that line solved the issue.

pablof
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1

I fixed my 'no wireless interfaces found' by joining all the groups that the default 'pi' user belonged to. The interfaces message only showed up when I was logged in as 'tech', not when I logged in as 'pi'. Of course, I almost never logged in as 'pi', so it was a happy accident that I discovered this.

I added about 10 groups to my 'tech' login, but I couldn't tell you which one did the trick. I added these groups: adm, dialout, cdrom, audio, video, plugdev, games, users, input, and netdev. I already belonged to sudo, gpio, i2c, and spi, and some others.

I'm not sure this will help anyone else, but it fixed my problem.

tstorm
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1

You need the firmware for your dongle. Some install will be already on your device but try:

apt-get update 
apt-get install git-core binutils rpi-update

then make sure you have the last kernel in place

rpi-update

get a bunch of firmware.... yes, a lot. You will Need some disk space, near 80Mb.

git clone http://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git

copy your firmware to the right place

mkdir /lib/firmware
cp linux-firmware/rt2870.bin /lib/firmware/rt2870.bin

and then your are free to delete the cloned files on your linux-firmware directory

fcm
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1

Probably the wireless adapter interface renamed to wlx_ _ _ _ _ _ _

(Predictable Network Interface Names: https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/).

  1. run dmesg and find something like this:

    [ 7.044805] rtl8192cu 1-1.2:1.0 wlx74da3833acb9: renamed from wlan0

This is the new name: wlx74da3833acb9

run iwconfig. In my case: 

wlx74da3833acb9  IEEE 802.11bgn  ESSID:"sysadmin"  Nickname:"<WIFI@REALTEK>"
      Mode:Managed  Frequency:2.437 GHz  Access Point: 10:FE:ED:E0:6C:96   
      Bit Rate:150 Mb/s   Sensitivity:0/0  
      Retry:off   RTS thr:off   Fragment thr:off
      Power Management:off
      Link Quality=100/100  Signal level=76/100  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

edit /etc/network/interfaces and rename wlan0 to wlxXXXXXXXXXX

In my case:

allow-hotplug wlx74da3833acb9
iface wlx74da3833acb9 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

reboot

  1. Or

edit: 

/lib/udev/rules.d/73-usb-net-by-mac.rules

comment everything: 

    # Use MAC based names for network interfaces which are directly or indirectly
# on USB and have an universally administered (stable) MAC address (second bit
# is 0).

#IMPORT{cmdline}="net.ifnames", ENV{net.ifnames}=="0", GOTO="usb_net_by_mac_end"
#PROGRAM="/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules", RESULT=="/d$

#ACTION=="add", SUBSYSTEM=="net", SUBSYSTEMS=="usb", NAME=="", \
#    ATTR{address}=="?[014589cd]:*", \
#    IMPORT{builtin}="net_id", NAME="$env{ID_NET_NAME_MAC}"

#LABEL="usb_net_by_mac_end"

reboot

boris
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I use a Raspberry Pi 2 model B with a wireless dongle usb realtek, with the current raspbian version show the error 'No wireless interfaces found'

I solve this problem using a old version for raspbian, can download it from https://downloads.raspberrypi.org/raspbian/images/raspbian-2019-04-09/

user143390
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I found several ^M in the /boot/config file. once remove wifi worked fine.

user145069
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Turns out that a change in /boot/config.txt created a similar issue for me! In my case the "interface was not found".

Puzzling because the changes in config.txt were to deal with HDMI display issues (trying to get a 5" monitor to work). Once restored to the original config.txt, WiFi resumed working normally without any change hardware or software change.

Mixie
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