Raspberry pi shows weird colours

Question

Hi, I bought this monitor to my pi 2: https://www.aliexpress.com/store/product/9-7-Inch-2048x1536-IPS-2K-Retina-Displayer-Screen-LCD-Module-Acrylic-Case-HMDI-Portable-Raspberry/1196030_32674549776.html

But it doesn´t work correctly. Look here: https://www.pixeltopic.com/image/rgxrhzqzqgfwmj/?size=full

I´ve tried to change the resolution in config.txt to 2048x1536, but it only makes it even smaller

Does anyone have any tips on how to fix it?

beacon_dave · Accepted Answer

Roger Wolff wrote:

...

Nowadays the monitor can electronically pass on the mode it wants through VGA or HDMI. The pi is "oldfashioned" in that it uses a list of possible modes and you HAVE to chose from those modes.... "back to the eighties". :-(

...

If you look here:

RPiconfig - eLinux.org

it suggests that the R-Pi does try to read the EDID data from the display and also gives you options to over-ride it:

" hdmi_ignore_edid Enables the ignoring of EDID/display data if your display doesn't have an accurate EDID."

and also to read it from a local EDID file, so as you could create your own if necessary.

" hdmi_edid_file when set to 1, will read the edid data from the edid.dat file instead of from the monitor. "

As has previously been suggested, there are also tools to verify the EDID data being captured by the R-Pi:

"Enter the following commands to dump more detailed information from your monitor

/opt/vc/bin/tvservice -d edid.dat

/opt/vc/bin/edidparser edid.dat"

Perhaps if the OP could post the output of that parsed EDID capture than it may help shed some light on the issue and to see if the EDID lists 2048x1536 as the preferred resolution and how the R-Pi scores it.

As for a previous comment about being restricted to the preset modes there also appears to be a custom CVT mode option:

https://www.raspberrypi.org/documentation/configuration/config-txt.md

which allows you to set up a custom CVT and access as a custom preset as:

group 2 mode 87

chejon · Answer

Thanks!! It works now. I made a custom CVT with group 2 and mode 87 and typed in the right resolution and hdmi_ignore_edid=0xa5000080 Thank you all for your replies

royleith · Answer

You can only set the desktop resolution to pre-set modes. The closest I could find for your screen is,

hdmi_group=2 ............................................(DMT)

hdmi_mode=84 ..........................................(2048x1152 Reduced blanking)

This would only fill part of the screen and the icons and text would be very small.

You can see the complete set at,

RPiconfig - eLinux.org

Since the screen is quite small and you want to use it with the Raspi Desktop I suggest you use one of the 1080p modes such as

sdtv_mode=2 .............................................(PAL as used in Europe)

hdmi_group=1 ............................................(CEA)

hdmi_mode=16 ..........................................(1080p 60 Hz)

Since it is intended for the Raspi, XBox and PS4, I would expect the screen to auto-configure to any of the broadcast standards. However, because it is intended for the American market, it may not respond to European modes. You might try the 'Which values are valid for my monitor?' section on the eLinux web page.

royleith · Answer

As I said, the display should auto-configure to a range of resolutions. What about,

hdmi_mode=73 ................................................. 1920x1440 60 Hz

hdmi_mode=62 ...................................................1792x1344 60 Hz

as well as the modes you listed.

However it is best not to guess at the supported modes. Have you tried the mode test?

Which values are valid for my monitor?
Your HDMI monitor may support only a limited set of formats. To find out which formats are supported, use the following method.

Set the output format to VGA 60 Hz (hdmi_group=1 hdmi_mode=1) and boot up the Raspberry Pi
Enter the following command to give a list of CEA supported modes
/opt/vc/bin/tvservice -m CEA
Enter the following command to give a list of DMT supported modes
/opt/vc/bin/tvservice -m DMT
Enter the following command to show your current state
/opt/vc/bin/tvservice -s
Enter the following commands to dump more detailed information from your monitor
/opt/vc/bin/tvservice -d edid.dat
/opt/vc/bin/edidparser edid.dat

Of course, the hdmi_mode=1 may not work so try some others until you can, at least, read the text on the screen.

royleith · Answer

C J wrote:

Ok, here´s what I got: https://www.pixeltopic.com/image/stdbtxfwncvswba/?size=full
It just says: 640x480 60hz, so what does that mean?

Then I tested with hdmi_mode 84; 2048x1152
And it got a lot better: https://www.pixeltopic.com/image/hykhlemkpyusbjg/?size=full

But it´s still problem at the bottom, I´ve tried with overscan_bottom, but nothing happens?

It means that the screen responds to modes in Group 1 and Group 2, but only reports the current display mode. When displaying 640x480 @ 60Hz it puts the display top-left and fills the rest of the display with garbage data rather than doing resolution conversion. This is not a good sign.

Testing with hdmi_mode 84; 2048x1152 shows that it will work with higher resolution modes in Group 2, but that it does not do resolution conversion at the mode chosen. However, that is not a 5:4 mode.

Now try it with the following Group 2 modes,

hdmi_mode=73 ................................................. 1920x1440 60 Hz

hdmi_mode=62 ...................................................1792x1344 60 Hz

hdmi_mode=51 .......................................................................1600x1200 60 Hz

hdmi_mode=42 .......................................................................1400x1050 60 Hz

hdmi_mode=32 .......................................................................1280x960 60 Hz

hdmi_mode=16 .......................................................................1024x768 60 Hz

and see if any of them fill the screen. I doubt whether any monitor not intended as a computer screen will do resolution conversion for the old VGA modes. There is a much better chance at these higher resolution. Even though the screen is small, its high vertical resolution should make it usable at 1920x1440 so try that, first.

The overscan modes only affect where the desktop appears in the display area. If you set overscan top, left, right, and bottom, you will just get a blank frame around the desktop. In your 2048x1152 example, that would happen around the main image and also around the lower, truncated image. Overscan does not drive the monitor: it just changes how much of the monitor display area is used for the Desktop.

rew · Answer

It is really annoying that you cannot specify what resolution you really want. We started out like that with harddisks. You just had to specify type 1,2 3 or 4, not the hard stuff with cylinders and heads. That's when they made a few new harddrives and the table of drives got bigger and bigger until finally they got smart and gave us a screen where you could put in the numbers from your actual drive.

The same thing happened with screens and resolutions. In the beginning you had a few modes you could chose from and you'd chose the best one for your monitor. But eventually the number of modes and monitors became too large so that you had to use a standard resolution from a table or design your own given the numbers from the manual of your monitor.

Nowadays the monitor can electronically pass on the mode it wants through VGA or HDMI. The pi is "oldfashioned" in that it uses a list of possible modes and you HAVE to chose from those modes.... "back to the eighties". :-(

Your monitor has a "weird" resolution that is not common. So there is no ready-made resolution for your monitor.

With your monitor having so many pixels you might also run into a limitation of the hardware of the pi. There are just so many pixels that the pi can put out each second. 1920 x 1080 x 24bits x 60fps = 373Mbyte per second is something the pi can do for sure, but if the pi can handle the 566Mbyte per second that your display requires at 60FPS, I'm not entirely sure....

(and with the architecture of the pi, the CPU and the display share the bandwidth to the memory. So if you start using 600 Mbyte per second of bandwidth for the display, the CPU might start noticing the reduction in available bandwidth).