Using a high screen resolution on Raspberry Pi 4 can kill Wi-Fi
A strange bug has been discovered with the Raspberry Pi 4 which sees Wi-Fi failing when the screen resolution is set to 2560 x 1440.
Numerous users have taken to online forums -- including the official Raspberry Pi support forums – where various workarounds have been discussed. Of course, the simple solution to this problem is to use a lower resolution, but the root causes of it are still under investigation.
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Software developer Enrico Zini has written about the problem, explaining how to reproduce it. Outlining the issue, he says: "One full day of crazy debugging, and the result is that if the Raspberry Pi 4 outputs HDMI at a resolution of 2560x1440, the Wi-Fi stops working. Any lower resolution we tried, from 2048x1080 down, does not show this problem".
It does not appear to be an isolated problem. Not only have numerous other people stumbled across the same issue, Zini conducted his own investigation and was able to reproduce it in a number of circumstances:
- on both microHDMI outputs
- with two different cables: one with a microHDMI to HDMI dongle adapter, one direct microHDMI to HDMI
- with three different RaspberryPi units
- with 4 different power supplies: one rated at 2A, one rated at 3A, one rated at 3A bought in the Raspberry Pi shop in Cambridge, and a laptop USB-C charger
- with stock Raspbian Buster Lite
- with stock Raspbian Buster
- killing every process in the system, starting the network manually with wpa_supplicant and dhclient, and starting X manually with sudo X
- with two different SD cards
- connected to an AP some meters away, and connected to a phone hotspot next to the Raspberry PI
There is a discussion thread on Hacker News where there is speculation mimicking that found on the Raspberry Pi forums that cable shielding could be an issue.
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