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A comment on Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen resolution. Parent comment

Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by ChrisRR on Thursday November 28, 2019 @03:29AM (#21655556)
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.

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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by kingosticks on Thursday November 28, 2019 @04:50AM (#21655911)
> Because what if it's not?

Then, after you done ruling out the most likely and easiest explanation to test, you can then start exploring the remaining possibilities. Skipping to the more exotic explanations sounds more interesting but it's poor use of time if there's still low-hanging fruit out there.

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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by baq on Thursday November 28, 2019 @05:58AM (#21656221)
maybe, with high frequency radios and improperly shielded cables and chips, the most likely scenario is RF interference?
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by kingosticks on Thursday November 28, 2019 @06:02AM (#21656237)
Improper shielding is an assumption with no evidence as yet. I also mentioned that the ease of verifying the explanation should be a factor. Changing software is usually very easy.
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by markus92 on Thursday November 28, 2019 @06:49AM (#21656505)
It's so common that it's not an unlikely starting point. EMC is a major issue in high frequency electronics design and the raspberry pi had a history of having to redesign certain parts because of not having enough shielding.
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by kingosticks on Thursday November 28, 2019 @07:40AM (#21656834)
I can find [1] on the subject which is quite interesting.

[1]: https://www.element14.com/community/people/PeteL/blog/2012/0...

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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by markus92 on Thursday November 28, 2019 @08:53AM (#21657331)
See also https://www.raspberrypi.org/blog/tag/ce-compliance/
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by kingosticks on Thursday November 28, 2019 @09:26AM (#21657562)
There doesn't seem to be much info on compliance out there for Pi 4 which must have been significantly different w.r.t HDMI.
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by markus92 on Thursday November 28, 2019 @10:53AM (#21658143)
Absolutely, and this was before the Pi had built-in Wifi. The norms you have to comply for are immediately a lot stricter as your device falls into a different category (telecommunications devices).
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by mlyle on Thursday November 28, 2019 @02:04PM (#21659510)
https://twitter.com/assortedhackery/status/12000566338980290...

Evidence :P

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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by baq on Thursday November 28, 2019 @06:05AM (#21656252)
wrapping tinfoil around an hdmi plug/cable isn't particularly hard either :) chips are harder but at least you rule out the cable. HDMI cables are ridiculously finicky if you've ever tried to get anything more than the lowest common denominator 1080p going on them.
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Re:Raspberry Pi 4 WiFi stops working at 2560 x 1440 screen r... by kingosticks on Thursday November 28, 2019 @06:18AM (#21656316)
I don't agree that wrapping foil is a great way to 100% rule that out as there is room for error. Using different cables/dongles would be better and they already tried that.
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