Pi 4 4GB- Wifi not working when resolution is set too high

[scarecrowsong]

Hello folks, I have the strangest issue with my Pi4 4Gb model. If the resolution is set to 1920x1080 or 1024x768 the wifi sees the APs but will not connect. No error message just type in the password and it never connects. If however, I set my resolution to 800x600 everything works as normal. Why would the resolution have anything to do with the wifi issue??? Also for reference I am using the official PSU and have nothing extra plugged into the Pi4. HALP!

[EnricoF]

Hi to all,
Luckily I found this post, I was becoming crazy.
I have the same problem can not connect to the wifi.
So I made same test at different resolution.
I connected to the access point at a lower resolution and then try to load fast.com at different screen resolutions.
Here the results (yes = works):

1920x1080 yes
1600x1200 no
1680x1050 yes
1280x1024 no if switching from 1600, yes if 1440 or 1680
1440x900 yes
1280x960 yes
1280x800 yes

Very wired behavior
Some idea?

Enrico

[HawaiianPi]

Odd problem.

First thing that comes to mind is a poorly shielded HDMI cable (or adapter)?

[EnricoF]

The HDMI cable is the official one supplied by the online shop.
An external usb wifi dongle works perfectly to any resolution.
I discover the problem after updating my pi today. ( apt-get dist-upgrade) Not sure was there before.
The pi is the 4GB one.

[HawaiianPi]

Are you using any USB 3.0 devices?

USB 3.0 is known to interfere with 2.4GHz wireless?

[EnricoF]

Thanks for yours replay.

Test made with only keyboard and mouse into usb2 ports.

The external usb wifi dongle, connected to usb3, that always work have an external antenna and it's very close to the pi too.

The wpa_supplicant error shown in wpa_cli is wrong authentication error.

Don't you have the same problem? Have you tested?

[timg236]

Please can you check for any mmc or SDIO errors in dmesg in the failing case ?

It might be worth adding these lines in config.txt to rule out clock configuration to SDIO issues before thinking about RF interference

core_freq=500
core_freq_min=500

[EnricoF]

Can not find any error, nor one related to mmc or SDIO in dmesg.

Adding the two line:
core_freq=500
core_freq_min=500
in config.txt doesn't fix the problem

In my config.txt I have the line:
hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
config_hdmi_boost=4
hdmi_group=2
disable_overscan=1

because I'm using a tv Asanzo model 32T660N and it was the only way to get HDMI video out.
Just to say a Chromcast ultra works perfectly.

[HawaiianPi]

Don't you have the same problem? Have you tested?

WiFi on my two Pi4s is not as good as some other computers I own, but it's not the worst either, and I have no trouble connecting to my router (located down the hall in another room). My wpa_supplicant.conf has both 2.4 and 5GHz networks, and it usually connects to the faster 5GHz.

[amgrays]

I have had similar problems:
- in one location, removing the USB card reader from USB3 to USB2 socket appeared to resolve the issue (I managed to destroy a 32G card while plugged into the USB3 port for some reason but that is another issue - or maybe related)
- in another location I have managed to pretty much proved that having a monitor plugged into HDMI0 causes WiFi to fail (haven't tried changing resolution but have it set in config.txt as follows:

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hdmi_force_hotplug=1
hdmi_force_mode=1
hdmi_group=2
hdmi_mode=42

Steps to reproduce are:

• Boot with monitor off
• Ensure WiFi connected OK and ping google.com - responses shown
• Turn on monitor - responses stop

I then plugged the monitor into HDMI1 and the problem disappears.

BTW I have an official Raspberry Pi power supply but I can't help feeling that this is a power-related hardware issue rather than software config.

[mahjongg]

Sounds like HDMI signals interfering with Wifi signals to me.

[amgrays]

Some test results on HDMI0, hdmi-safe=1 (640x480 60Hz). Monitor connection is with 10cm micro HDMI to female HDMI connected to standard HDMI M-M (approx 2m)

1) Monitor unplugged: Av = 56ms

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--- google.com ping statistics ---
87 packets transmitted, 85 received, 2.29885% packet loss, time 255ms
rtt min/avg/max/mdev = 41.953/55.984/180.752/29.012 ms

2) Monitor plugged in to HDMI0: Av = 585ms

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--- google.com ping statistics ---
86 packets transmitted, 83 received, 3.48837% packet loss, time 443ms
rtt min/avg/max/mdev = 39.836/584.915/1448.568/478.726 ms

3) Monitor plugged in to HDMI1: Av = 123ms

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--- google.com ping statistics ---
94 packets transmitted, 84 received, 10.6383% packet loss, time 635ms
rtt min/avg/max/mdev = 41.775/123.215/555.718/98.295 ms

So, even though WiFi is still operational, WiFi performance is significantly degraded with monitor connected to HDMI0. There is less degradation when the monitor is connected to HDMI1. Interference between HDMI and WiFi seems like a plausible scenario. In the meantime suggestions are:

• Use HDMI1 output connector
• Use the lowest resolution possible
• Don't use WiFi
• Wait for the next hardware iteration that will hopefully fix the issue

[jamesh]

Some test results on HDMI0, hdmi-safe=1 (640x480 60Hz). Monitor connection is with 10cm micro HDMI to female HDMI connected to standard HDMI M-M (approx 2m)

Do you have a cable that does NOT need the adapter, preferably 1M? I wonder if the adapter cable and/or the extra plugs, are leaking RF.

[amgrays]

Do you have a cable that does NOT need the adapter, preferably 1M? I wonder if the adapter cable and/or the extra plugs, are leaking RF.

No I don't but will get one and report back. Would that explain a significant different between HDMI0 and HDMI1?

[wxtb]

Hi together,

I am observing same issue. Following my experience:

I setup my new Pi 4 yesterday and was quite surprised it doesn't connect to wireless LAN. To play with the Pi I took cable for Internet connection which was ok. Within dmesg and journalctl I didn't see attempts for connection.

General setup

• attached USB hub for keyboard and mouse
• using original power supply
• with first attempts there was no USB3 stick attached; with latest working attempts USB3 stick was attached

Today I thought lets try again and use Internet for help.

• First I tried to connect to Hotspot from smartphone and it worked. Trying to connect to wireless LAN router at home afterwards didn't do anything. No message within dmesg.
• Afterwards I found a post where somebody was suggesting a smaller resolution. I switched from 1920x1200 to 1024x768 and ping was working. Switching back to 1920x1200 stopped ping immediately. Switching to 1024x768 resulted again in successful ping.
• Then I found this post and I changed to cable directly connecting microHDMI to HDMI. Cable is 1.8 m long. And wireless LAN is working with high resolution. Before I had microHDMI to HDMI adapter with ~10cm cable.

For me it sounds like like a hardware/design issue. Or is there an other explanation?

[Aardappeltaart]

Probably related issue:
RPI4 set up as accesspoint is dropping devices when playing something on KODI.
https://www.raspberrypi.org/forums/view ... 8&t=255870

Did help when i choose higher WIFI channels.

Do you see differences choosing higher 2.4Ghz WIFI channels?

[wxtb]

I made some more tests. In my case the situation shows up as following

Using microHDMI to HDMI cable 1.8 m (no adapter)

• all wireless LAN channels --> ok
• doesn't matter if USB3 stick is connected --> ok
• screen resolution 1920x1080 --> ok

Using microHDMI to HDMI adapter ~10 cm cable and ~1.8 m HDMI cable

• changing wireless LAN channel to channel below 10 --> ok
• resolution 1024x768 slow and failing pings. This was ok yesterday --> not ok
• resolution 1920x1200 no wireless connection at all --> not ok
• doesn't matter if USB3 stick is connected at 1920x1200 --> not ok
• all other resolutions work --> ok

Disconnecting HDMI cable works as well --> ok

I didn't test for 5 GHz band so far. Changing transmit power to lower values within router didn't change anything. Changing the 802.11 Mode didn't help at all.

Here the link to another discussion about wireless connection issue:
https://www.raspberrypi.org/forums/view ... p?t=247982

Reading through the posts show that for different Raspberries different settings work. Settings which work for one may not work for the other. Like in my case I need exactly opposite wireless channels compared to another guy.

[semaf]

I made some more tests. In my case the situation shows up as following

Using microHDMI to HDMI cable 1.8 m (no adapter)

• all wireless LAN channels --> ok
• doesn't matter if USB3 stick is connected --> ok
• screen resolution 1920x1080 --> ok

Using microHDMI to HDMI adapter ~10 cm cable and ~1.8 m HDMI cable

• changing wireless LAN channel to channel below 10 --> ok
• resolution 1024x768 slow and failing pings. This was ok yesterday --> not ok
• resolution 1920x1200 no wireless connection at all --> not ok
• doesn't matter if USB3 stick is connected at 1920x1200 --> not ok
• all other resolutions work --> ok

Disconnecting HDMI cable works as well --> ok

I didn't test for 5 GHz band so far. Changing transmit power to lower values within router didn't change anything. Changing the 802.11 Mode didn't help at all.

Here the link to another discussion about wireless connection issue:
https://www.raspberrypi.org/forums/view ... p?t=247982

Reading through the posts show that for different Raspberries different settings work. Settings which work for one may not work for the other. Like in my case I need exactly opposite wireless channels compared to another guy.

Can you post the brand and model of the 1,8m micro HDMI cable?

[Aardappeltaart]

Also came to the conclusion that the HDMI cable/interference is the cause here.

Changed the cable, and it solved my problems. It the meantime I also tweaked some minor things, but I don't see the problem anymore after choosing a lower channel number.

[K9spud]

Hey guys, I've got another possible workaround for your RPi4 WiFi problems... Turn off your Access Point. Reboot the Raspberry Pi 4 and get all the way logged into your GUI desktop. Then turn on the Access Point. Boom, WiFi connects and works, no need to switch to HDMI port 1.

From my perspective, it seems like if the Raspberry Pi 4 tries to associate with the access point too early during boot up, there is too much other stuff going on at the same time and something in software gets stuffed up, making it so that I can "see" available WiFi access points, but I can't connect to them. If I avoid having the Raspberry Pi 4 connect to my access point during that busy boot up period, things seem to work fine.

As other people have mentioned, avoid having USB 3.0 hard drives hooked up, as they can cause 2.4GHz interference. My WD Passport 2TB USB 3.0 drive is notorious for causing such problems for me if I forget to unplug it.

I'm using Raspberry Pi 4/4GB with a micro-HDMI to DVI cable on HDMI port 0 at 1920x1200 resolution. I'm connecting to an Android cell phone over 2.4GHz WiFi for tethered Internet access. I'm using the latest Raspbian 10 "buster" with EEPROM bootloader: Tue 10 Sep 2019 10:41:50 AM UTC / 000137ab.

[wxtb]

I did some new tests today. I went to my local reseller and got some different adapter without 10 cm cable but one solid block converting microHDMI to HDMI. Additionally I got some Raspberry Pi 4 with 2 GB, mine is a 4 GB version.

The test today mainly used my standard faulty setup:

• WiFi channel >10
• resolution 1920x1200
• nothing connected on USB3
• original power supply
• latest Raspbian with desktop
• HDMI cable bought from Amazon "KabelDirekt - 4K HDMI Kabel - 2m", ASIN B004BEMD5Q
• 64 GB SanDisk Extreme A2 microSD card

Findings

• doesn't matter if microHDMI to HDMI adapter as solid block or a different one with 10 cm cable in between is used --> not ok
• doesn't matter if 2 GB or 4 GB version of Raspberry Pi is used --> not ok
• doesn't matter if different router is used --> not ok

I tested for working connectivity by pinging WiFi router. What I have seen today that sometimes a ping was possible with my faulty configuration as well. Nevertheless it stopped at some point. Especially just touching the insulation of the microHDMI to HDMI adapter cable at the wrong position stopped the ping reaching router. I did one try opening a website when ping was ok in faulty configuration.

One more point to add is that WiFi network is found. The name is shown in the network manager. But connection is not established in faulty configuration.

Each single change in the following least leads to working WiFi (at least for now). So only one change necessary.

• using no converter
• using WiFi channel below < 10 (not really a good option when using Pi in different places)
• using monitor resolution different than 1920x1200 (in my opinion no option)

It would be great to get a reply from engineers for clarification and if they can reproduce it.

[jamesh]

I've just tried a standard HDMI cable with an adapter running to a Dell monitor at 1920x1200, using 5G Wifi, and it seems fine.

Note, using an adapter is not our recommended setup. You should use a uHDMI to HDMI cable for best results.

[Diablo2_Fan]

Each single change in the following least leads to working WiFi (at least for now). So only one change necessary.

• using no converter
• using WiFi channel below < 10 (not really a good option when using Pi in different places)
• using monitor resolution different than 1920x1200 (in my opinion no option)

Would you test this script with your standard setup, please?
It turns off the video output for 30 seconds, gets the iwconfig-values (wifi signal strength / noise level) and reactivates the video output:

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#!/bin/bash

echo "values with enabled hdmi:"
echo
iwconfig wlan0
sleep 1
echo
echo
echo "values with disabled hdmi:"
echo
vcgencmd display_power 0
sleep 30
iwconfig wlan0
sleep 1
vcgencmd display_power 1
read -n 1 -s

And would you please try wrapping the HDMI adapter in aluminium foil multiple times / generously?

[wxtb]

Thanks for replies.

Sorry I was not clear enough. I didn't test for 5 GHz WLAN up to now. A very quick test just now showed working Pi for 5 GHz. I checked for the first 2 options only.

The output of the script is (I replaced SSID and MAC address):

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values with enabled hdmi:

wlan0     IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=31 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on
          


values with disabled hdmi:

display_power=0
wlan0     IEEE 802.11  ESSID:"xxxxxxxxxx"  
          Mode:Managed  Frequency:2.462 GHz  Access Point: xx:xx:xx:xx:xx:xx   
          Bit Rate=65 Mb/s   Tx-Power=31 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on
          Link Quality=48/70  Signal level=-62 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

display_power=1

For the wrapping I need bit more time.

[kingosticks]

Previous Pi generations could use the

Code: Select all

config_hdmi_boost

setting in config.txt to control the HDMI "signal strength". The documentation claims that setting is ignored by the 4B, is that still the case? Has anyone tried playing with it?