Enrico Zini

Raspberry Pi 4 WiFi stops working at 2560x1440 screen resolution

This is part of a series of post on the design and technical steps of creating Himblick, a digital signage box based on the Raspberry Pi 4.

One full day of crazy debugging, and the result is that if the Raspberry Pi 4 outputs HDMI at a resolution of 2560x1440, the WiFi stops working.

Any lower resolution we tried, from 2048x1080 down, does not show this problem.

We reproduced this:

• 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

At the bottom of this forum thread (guestxyz dated Aug 07) someone mentioned screen resolution, which is what finally prompted us to try that. Thanks, guestxyz!

After confirming what the trigger was that caused the problem and chatting about it on IRC, olasd found this forum thread where more people are experiencing similar issues.

Further things left to try after chatting about it on IRC:

• whether disconnecting the HDMI cable from the Pi end (with X still started at high resolution and everything) make the WiFi work again
• switching the monitor to another input while the Pi is at 2560x1440
• letting the monitor go into power saving mode while the Pi is at 2560x1440
• cable chokes

Generated with staticsite on 2019-11-28 02:00:02.794868+01:00.

from Hacker News https://ift.tt/2XQwjVM