Networking interfaces disappeared from my RPI 4B 4GB

Question

Since receiving this Pi I've installed and configured Octoprint for my printer.

It ran fine without issues for 3-4 days, until I got disconnected when checking from work. Once home I found the Pi in a disconnected (from network) state. Unable to troubleshoot at the time because of the micro HDMI port and lack of networking, I bought myself a micro HCMI cable and a new Pi (just in case).

When the parts were received the - what I now call "old pi" - old pi didn't connect. It booted up but was unable to bring up any network interfaces, both wireless and wired. It claimed the interfaces did not exist.

Without changing anything I threw the SD card in the new Pi, which happily connected to wi-fi on first boot. Moving the card back to old Pi has the same result - no networking available.

From what I can tell the USB works fine. I'm pretty sure this is a hardware issue as the SD card and its configs work properly in new Pi.

Did I simply get unlucky with old Pi? Is there anything I can test to make sure?

Update 2019-11-10

I've put the fully functional SD card into the old pi to troubleshoot a bit more;

• ifconfig shows only "lo" as interface

• ip a shows "lo" and "eth0"

• ifup eth0 results in unknown interface (as expected, /etc/network/interfaces is empty

• ls /sys/class/net shows "lo" and "eth0"

• dmesg may have the most information, as it says;

bcmgenet fd580000.genet eth0: failed to connect to PHY

There's a few more red lines all to do with brcmfmac which i think is related to audio as it's stating soc:audio previously. It says brcmfmac: brcmf_chip_recognition: chip backplane type 15 is not supported.

The setup is identical (network, wires, sd card) to the working pi.

From my DHCP server I'm unable to find any connection attempts from this Pi when connected over wired ethernet.

The Pi is uncomfortably hot to touch, and vcgencmd displays it at 67 degrees C just after the troubleshooting above. The other Pi reaches 55C while printing.

Answer 1

If ip link does not show the wifi interface either you need a different kernel or the board has been physically damaged. If the exact same card works in another model 4 then the problem is not the kernel.

The heat problem and the system log errors are consistent from this (defunct hardware). There maybe a slim chance that the chip is busted in such a way that if you can keep it cool enough it will work; I have MCUs that has happened to, and they are a PITA.

Again, that's a slim chance.