minwah
Posts: 3
Joined: Sat Aug 10, 2019 8:24 pm

RPi 4 Raspbian Buster desktop resolution

Sat Aug 10, 2019 8:52 pm

Hi there,

I've used Raspbian Lite quite a bit before, but am new to the Raspbian desktop GUI so please forgive my ignorance...

I've got a Pi 4 hooked up to a VGA monitor via HDMI > VGA adaptor. The monitor only works with the Pi's 640x480 and 800x600 modes. I have set my config.txt accordingly to use 800x600 (60Hz):

hdmi_group=2
hdmi_mode=9

This works fine in the terminal but in the desktop it selects a mode outside of the range of the CRT (it does display something, but messed up and illegible, looks to be a very high resolution). I gather this is the desktop selecting what it thinks to be a good video mode. I doubt EDID works with VGA adaptors so not sure what it is doing exactly.

I found that I can set the video mode using this command:

xrandr --output HDMI-1 --mode "800x600"

This works fine...until I reboot and then it's back to the world of guessing what I'm typing.

What is the best way to autorun this command on startup? I did some research and thought that editing (sudo nano) /etc/xdg/lxsession/LXDE-pi/autostart would be the way to go, and added my above command (prefixed with @). This doesn't seem to do anything. I had a look in ~/.cache/lxsession/LXDE-pi/run.log and it contains this:

app.vala:76: Launching xrandr
xrandr: cannot find mode "800x600"

As I say, the command works manually from a terminal so not sure what the problem is. If anyone could point me in the right direction it would be much appreciated!
Last edited by minwah on Mon Aug 12, 2019 12:17 pm, edited 1 time in total.

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Gavinmc42
Posts: 3642
Joined: Wed Aug 28, 2013 3:31 am

Re: RPi 4 Raspbian desktop resolution

Sun Aug 11, 2019 12:57 am

Does that monitor have a DVI input?
They just work.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

minwah
Posts: 3
Joined: Sat Aug 10, 2019 8:24 pm

Re: RPi 4 Raspbian desktop resolution

Sun Aug 11, 2019 11:05 am

Gavinmc42 wrote:
Sun Aug 11, 2019 12:57 am
Does that monitor have a DVI input?
They just work.
No, it only has VGA.

The monitor works fine, it is something desktop is doing that is the problem. It was not a problem on Pi 2 using the same OS (Raspbian Buster).

minwah
Posts: 3
Joined: Sat Aug 10, 2019 8:24 pm

Re: RPi 4 Raspbian desktop resolution

Sun Aug 11, 2019 11:11 am

Here is a thread where someone had the same problem and used xrandr to solve it:

https://www.raspberrypi.org/forums/view ... ?p=1500094

In there pik33 says:

'If you add this to X autostart script, it should set your needed graphics mde in X'

That is the part I'm struggling with...

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