Had the same problem with Raspi 4B.
Problem was dependent on screen resolution (!!).
With 1920x1080, wlan0 became disconnected after it was
ok at lower screen resolutions. Was in 2.4GHz band.
After turning on 5GHz in the router and going into
the network preferences (right click the network icon top
right on screen) and SSID ... and checking "automatically
configure options" the connection remains stable (so far :D ).
Had the same problem with Raspi 4B. Problem was dependent on screen resolution (!!). With 1920x1080, wlan0 became disconnected after it was ok at lower screen resolutions. Was in 2.4GHz band. After turning on 5GHz in the router and going into the network preferences (right click the network icon top right on screen) and SSID ... and checking "automatically configure options" the connection remains stable (so far :D ).
Reminds me of the MacBook Air that I have (2018 model).
When I connect my USB 3 hub to it, I lose my WiFi :(
I Googled it when it happened a while back, and apparently other people have this problem with the MacBook Air too.
Some choose to shield the USB 3 cable with tinfoil. Personally I opted to connect a USB 3 Ethernet interface to the hub and use wired Ethernet when I use the hub.
Yes, although Eben Upton suggests trying a better grade of HDMI cable... the frequency of the higher resolution on screen will radiate noise out of a poorly shielded cable enough to interfere with Wi-Fi in the 2.4Ghz range.
Don't use a cheap cable, use one rated for 4k, and see if that helps.
I will really like to hear what the root cause of this is.
This makes me think of the bug that the QCA AR9331 SoC has. The AR9331 is extremely common in small travel routers, but it has a fun bug where one of it's clock sources is shared between the 802.11 wifi and the USB port. IF the USB port is negotiated at USB 1.x speeds AND the 802.11 radio is scanning, the USB will freak out and die. This generally requires the 802.11 radio to be in client mode rather than AP mode. You can read some details about this on the old OpenWRT forum, if it survived the great forum purge of 2018.
Unfortunately not only with cheap external USB 3.x drives and not only with old MacBook Airs. Connecting an Anker USB-C dock/hub to my MacBook Pro 2016 and later 2018 would consistently cause interference with the Microsoft Sculpt Ergonomic and Apple Magic Trackpad (both on 2.4GHz). Then I got an Aukey hub (since my wife was happy with one) and the problems have vanished.
Aw, I was hoping the explanation would be in the thread. Is it high-frequency noise from an unshielded clock? Surpassing a current or temperature limit due to the stress of the high resolution and resulting high memory bandwidth? Time will tell!
> Is it high-frequency noise from an unshielded clock?
I bet that's it.
2560x1440 @ 60 Hz with CVT-RB timings has a pixel clock of 241.5 MHz. The TMDS bit rate is 10x the pixel clock, and 2415 MHz is right in the lower end of the 802.11 band.
If the Pi can be convinced to use CVT blanking, that'll raise the pixel clock to 312 MHz, which should be fine.
Former communications semiconductor FAE here. We would troubleshoot issued like this all-day every-day for years, usually under NDA before the product is ever released to production. The solutions are routinely as weird as some of the "voodoo" hypothesis tossed around here - wait for it and you'll see. After a while it seems normal that all unverified combinations are broken and the moments of delight are when an unverified configuration completely works.
Why do all the proposed avenues of future investigation, and all of the current comments on this thread, focus on voodoo instead of the far more likely explanation that the display driver is just stomping on the memory of the network interface? If there's software anywhere in a system, 99% of the time that's the problem.
This is not true when radios are involved. In my experience, wireless connectivity issues are rarely caused by software; the problem is much more often caused by interference.
The interference can be internal interference in the device, or interference from other wireless devices. In many cases, the problem are even devices that shouldn't emit RF at all, like power supplies, switches, light bulbs...
Another common issue is poor antenna design (eg. attenuation when you hold the device, or strong directionality of an antenna that should not be directional).
And, last but not least, physical obstacles. Most people understand that concrete walls with rebar will block signal, but a surprisingly large number of people try to use aluminum stands or cases for devices with wireless radios.
All those factors will cause connection issues, and they are really common because debugging them is so hard (who has a spectrum analyzer at home? How do you find out which one of dozens of electronic devices is emitting RF that it shouldn't?)
In addition, the linked forum thread includes a user describing how high resolutions break 2.4GHz networks for them, but 5GHz networks work fine. The display driver is stomping on memory responsible for 2.4GHz, but not 5GHz? I'm really not seeing that as the more likely problem here.
So the display driver is meant to be mutating memory also owned by the network controller, but not in a way that causes a crash, log messages, or a kernel panic? That doesn't seem so likely to me. I mean it's not impossible but it's rare to see memory corruption/interference cause a clean breakage like this. In my experience it usually causes things to become extremely funky for a short while, then a crash.
Because what if it's not? My first thought is that the HDMI is radiating and interfering with the wifi antenna.
As an embedded engineer, it was a hard lesson for me to learn that not all issues are software issues and the hardware may need to be investigated.
This is especially true where there is different behaviour between units. You can't just assume that your 99% estimation (plucked out of thin air) is correct and discredit other potential explanations.
There's several small scale WiFi chips that share clock source with USB - it would be unsurprising to find that the WiFi and video interface are sharing the same clock, so drawing too much from either could directly effect the other.
These kinds of problems are common in embedded computers, like the Pi. Just as common as software.
I don't know much about the Raspberry Pi, but it looks like they chose an ARM core variant without IOMMU, so this might actually be plausible, even though it's such a computer architecture anti-pattern to share system memory DMA across devices.
Mostly because of a known history over the past couple years of USB, WiFi, and/or HDMI causing direct interference with each other. See lots of other comments upthread about similar RF issues people have had, stretching all the way back to 486 laptop keyboards :)
I don't know why it became such a piece of breaking news.
When a current flows through a p&n junction, photons are emitted (and an LED is just a diode that happens to emit photons at the wavelengths of visible light). And it works in both ways, if you hit a p&n junction with photons, you produce a current, not only LEDs - any diode will do that, they're all potential photodiodes, it's just that some are more sensitive than others.
You can cause a lot of chips to reset if you shine a bright beam of light to its exposed die, a common way to test chips.
It's also one reason (in addition to cost) that most diodes are sealed in plastic package, not glass package. Fun experiment: buy some 1N4148 small-signal diodes in glass package, connect it to a Darlington-pair transistor amplifier, and shoot the flashlight, you'll see some funny thing on the oscilloscope.
One of my professors told a story of reporters crashing one of AT&T's new digital exchanges because their camera flashes erased some of the EPROMS used in the system.
While it might seem a bit overkill try restarting your router’s WiFi to see if it magically works. I had a war with a pi zero W not that long ago...turns out the 2 band wireless would just die sometimes. Turned out to be an issue with the router ️
Monitors creating harmonic interference with wifi is a very common problem, and most computers don't give any warning of this. I don't see why it wouldn't be possible to say "the wifi won't connect, it may be because of your refresh rate".
The plane can't take off because the carpet is the wrong kind of orange.
ObligAnecdote:
I once had a keyboard that wouldn't work when the monitor was outputting at 75hz. Had to be 60hz or else nothing. The joys of wireless keyboards.
I have this issue with a Zero W. Wlan0 would just disappear. I tried jessie, stretch, and now buster. It had been connected to a ultra-wide monitor (but not at 2560 width, obviously).
I can't get it to fail now, but it is not connected to a monitor anymore.
[+] [-] adontz|6 years ago|reply
[+] [-] nkrisc|6 years ago|reply
Had the same problem with Raspi 4B. Problem was dependent on screen resolution (!!). With 1920x1080, wlan0 became disconnected after it was ok at lower screen resolutions. Was in 2.4GHz band. After turning on 5GHz in the router and going into the network preferences (right click the network icon top right on screen) and SSID ... and checking "automatically configure options" the connection remains stable (so far :D ).
[+] [-] codetrotter|6 years ago|reply
When I connect my USB 3 hub to it, I lose my WiFi :(
I Googled it when it happened a while back, and apparently other people have this problem with the MacBook Air too.
Some choose to shield the USB 3 cable with tinfoil. Personally I opted to connect a USB 3 Ethernet interface to the hub and use wired Ethernet when I use the hub.
[+] [-] Accujack|6 years ago|reply
Don't use a cheap cable, use one rated for 4k, and see if that helps.
[+] [-] _pmf_|6 years ago|reply
[+] [-] TwoNineFive|6 years ago|reply
This makes me think of the bug that the QCA AR9331 SoC has. The AR9331 is extremely common in small travel routers, but it has a fun bug where one of it's clock sources is shared between the 802.11 wifi and the USB port. IF the USB port is negotiated at USB 1.x speeds AND the 802.11 radio is scanning, the USB will freak out and die. This generally requires the 802.11 radio to be in client mode rather than AP mode. You can read some details about this on the old OpenWRT forum, if it survived the great forum purge of 2018.
[+] [-] pvtmert|6 years ago|reply
Wifi shows as 'connected' but reality is only fraction of packets go through because of interference problems
some online reference from intel on usb.org: https://usb.org/sites/default/files/327216.pdf
[+] [-] microtonal|6 years ago|reply
[+] [-] cjbprime|6 years ago|reply
[+] [-] duskwuff|6 years ago|reply
I bet that's it.
2560x1440 @ 60 Hz with CVT-RB timings has a pixel clock of 241.5 MHz. The TMDS bit rate is 10x the pixel clock, and 2415 MHz is right in the lower end of the 802.11 band.
If the Pi can be convinced to use CVT blanking, that'll raise the pixel clock to 312 MHz, which should be fine.
[+] [-] VT_Dude|6 years ago|reply
[+] [-] mceachen|6 years ago|reply
FAE = Functional Accessibility Evaluator
[+] [-] seminatl|6 years ago|reply
[+] [-] jakobegger|6 years ago|reply
The interference can be internal interference in the device, or interference from other wireless devices. In many cases, the problem are even devices that shouldn't emit RF at all, like power supplies, switches, light bulbs...
Another common issue is poor antenna design (eg. attenuation when you hold the device, or strong directionality of an antenna that should not be directional).
And, last but not least, physical obstacles. Most people understand that concrete walls with rebar will block signal, but a surprisingly large number of people try to use aluminum stands or cases for devices with wireless radios.
All those factors will cause connection issues, and they are really common because debugging them is so hard (who has a spectrum analyzer at home? How do you find out which one of dozens of electronic devices is emitting RF that it shouldn't?)
[+] [-] mjg59|6 years ago|reply
[+] [-] asdfasgasdgasdg|6 years ago|reply
[+] [-] avip|6 years ago|reply
[+] [-] ChrisRR|6 years ago|reply
As an embedded engineer, it was a hard lesson for me to learn that not all issues are software issues and the hardware may need to be investigated. This is especially true where there is different behaviour between units. You can't just assume that your 99% estimation (plucked out of thin air) is correct and discredit other potential explanations.
[+] [-] JshWright|6 years ago|reply
Unless USB is involved, then it's something in the USB stack...
[+] [-] shakna|6 years ago|reply
These kinds of problems are common in embedded computers, like the Pi. Just as common as software.
[+] [-] arcticbull|6 years ago|reply
[+] [-] cjbprime|6 years ago|reply
[+] [-] mjg59|6 years ago|reply
[+] [-] yipbub|6 years ago|reply
Try to reproduce with a different OS/kernel.
[+] [-] mlyle|6 years ago|reply
Actual measurement that a Pi with HDMI at the affected reoslutions radiates over the bottom end of the wifi band.
[+] [-] floatingatoll|6 years ago|reply
[+] [-] Animats|6 years ago|reply
[+] [-] forkerenok|6 years ago|reply
[+] [-] Dwolb|6 years ago|reply
[+] [-] _bxg1|6 years ago|reply
[+] [-] fulafel|6 years ago|reply
[+] [-] skittleson|6 years ago|reply
[+] [-] chx|6 years ago|reply
https://www.akitio.com/faq/301-why-does-my-thunderbolt-3-dev...
> Why does my Thunderbolt 3 device not work with Dell's XPS laptops?
> Some users on the Dell forum have found that reducing the power output of the WiFi network adapter to 75% fixes the problem.
[+] [-] cft|6 years ago|reply
[+] [-] cyberjunkie|6 years ago|reply
[+] [-] segfaultbuserr|6 years ago|reply
When a current flows through a p&n junction, photons are emitted (and an LED is just a diode that happens to emit photons at the wavelengths of visible light). And it works in both ways, if you hit a p&n junction with photons, you produce a current, not only LEDs - any diode will do that, they're all potential photodiodes, it's just that some are more sensitive than others.
You can cause a lot of chips to reset if you shine a bright beam of light to its exposed die, a common way to test chips.
It's also one reason (in addition to cost) that most diodes are sealed in plastic package, not glass package. Fun experiment: buy some 1N4148 small-signal diodes in glass package, connect it to a Darlington-pair transistor amplifier, and shoot the flashlight, you'll see some funny thing on the oscilloscope.
[+] [-] tallanvor|6 years ago|reply
[+] [-] SudoEpoch|6 years ago|reply
[+] [-] caro_douglos|6 years ago|reply
You were missing a router swap on your list.
While it might seem a bit overkill try restarting your router’s WiFi to see if it magically works. I had a war with a pi zero W not that long ago...turns out the 2 band wireless would just die sometimes. Turned out to be an issue with the router ️
[+] [-] mike_hock|6 years ago|reply
[+] [-] WilliamEdward|6 years ago|reply
[+] [-] smashah|6 years ago|reply
[+] [-] rs23296008n1|6 years ago|reply
The plane can't take off because the carpet is the wrong kind of orange.
ObligAnecdote: I once had a keyboard that wouldn't work when the monitor was outputting at 75hz. Had to be 60hz or else nothing. The joys of wireless keyboards.
[+] [-] forinti|6 years ago|reply
I can't get it to fail now, but it is not connected to a monitor anymore.
[+] [-] goombastic|6 years ago|reply
[+] [-] frou_dh|6 years ago|reply
https://developer.nvidia.com/embedded/jetson-nano-developer-...
Don't let the AI-heavy marketing distract. It's an Ubuntu PC effectively.
[+] [-] gonesilent|6 years ago|reply
[+] [-] jrockway|6 years ago|reply
[+] [-] tyingq|6 years ago|reply
[+] [-] mic-kul|6 years ago|reply