How to repair WiFi on RPi4 with Buster?

[Bosse_B]

I am in a bit of a problem now...
A couple of weeks ago I started experimentation in order to set up my RPi4 as a WiFi AP while connected by mobile network. My thread about this is here.

I did not have a mobile connection at the time so I was on wired Ethernet and used VNC and PuTTY to do the experiments.

It never panned out and then I tried to undo what I had done to get my system back into the state it was previously, but this also failed.

I can connect by PuTTY and VNC through ethernet but I can for the life of me not get WiFi working normally again!

I then had to go to the USA for a couple of weeks so I am only now back home trying to fix the problem.

When in VNC on the desktop I cannot use the top right icon to connect to a WiFi network.
When I click on the double arrow symbol all I see is "No wireless interfaces found".
But on PuTTY I get this:

Code: Select all

$ ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.119.246  netmask 255.255.255.0  broadcast 192.168.119.255
        inet6 fe80::fffa:e103:a4c9:1230  prefixlen 64  scopeid 0x20<link>
        ether dc:a6:32:05:6c:d9  txqueuelen 1000  (Ethernet)
        RX packets 466  bytes 136979 (133.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 237  bytes 67681 (66.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 9  bytes 524 (524.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 9  bytes 524 (524.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlan0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether dc:a6:32:05:6c:db  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

To me that indicates that interface wlan0 exists and is enabled, why can it not be used?

Any ideas where I should look to get it going again?

[DougieLawson]

Start with sudo apt update && sudo apt dist-upgrade -y && sudo reboot.

If that doesn't work, try a new SDCard with a fresh copy of Raspian 2019-09-26.

[Bosse_B]

Thanks for the quick reply!
I had already done apt upgrade so now I also tried the dist-upgrade.
But after it was done and it had rebooted the same problem is present...
Maybe Raspbian does not allow simultaneous connection by Ethernet and WiFi?

I could check the hardware by using a new SD-card, but I have a ton of dev tools installed on the existing card so the new card test would only be to verify if there is a hardware problem on the WiFi.
But in the end I need to figure out what has broken on the original card implementation so it can be undone...

[neilgl]

Maybe Raspbian does not allow simultaneous connection by Ethernet and WiFi?

Yes it does allow simultaneous connections by Ethernet and Wifi. (I get 2 seperate ip addresses, via DHCP)

[Bosse_B]

OK, so now I have successfully started up my RPii4 with a Buster-Lite SD image 2019-09-26.
The WiFi works OK as does Ethernet.
In fact I added a wpa_supplicant.conf file to the /boot section (FAT) on the SDcard before I booted it up.
I entered my own WiFi network settings there and the RPi4 automatically connected upon boot.

Are there any specific files I could copy from this version and overwrite on the original (full Buster version) SD-card to get WiFi back working?

Or is there some other configuration change I have to do or logfile or such to check on the full version RPi4 I want to use in view of the amount of tools I have installed there?