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Problem with an HDMI 7 inch LCD (Waveshare)
#1
Hi,

yesterday I received a Waveshare 7" LCD (with touchscreen and HDMI input, 800x480), I briefly tested it with my Windows 7 laptop, everything worked out good (except for the touchscreen).
When I arrived at home I tried to install the Waveshare Raspberry image (PI2) and everything worked out, touchscreen included.
Just to have a try with Kodi (I will use the LCD for a car media center) I installed it directly from Raspbian but at the end of the installation when I launched Kodi, a lot of "garbage" appeared on the screen.
It's not easy to describe but this "garbage" made almost all the screen area white with dark lines !
The Raspberry was still running since I rebooted it via SSH.
I checked then the "config.txt" but the HDMI parameters (incliding "max_usb_current=1") was there correctly.

Code:
hdmi_cvt=800 480 60 6
hdmi_group=2
hdmi_mode=87
hdmi_drive=2

Then I tried to install a fresh copy of Raspbian (not the one supplied by Waveshare), made all the "update", configured the "config.txt" with HDMI parameters, installed Kodi from within Raspbian but I had the same problem: white screen with dark lines (the Raspbian desktop was barely visible in the background).
I tried also to install Kodi as standalone but when it "switches" to the main screen, the garbage appears.
It seems that, for some reason that I don't know, the HDMI/video settings when Kodi activates are wrong, while everything works good with Raspbian !
Should it get the video settings from the config.txt?
What could I check?
Thank you, best regards.

Roberto
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#2
If you add hdmi_force_mode=1 to config.txt then only that mode will be detected by Kodi, and it should avoid switching resolution.
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#3
Thanks, I will try it.
Regards,


Roberto
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#4
I tried but nothing changed.
Well....actually something changed...after 30/40 sec. of "garbage" on the screen, the main menu appeared.
I noticed that everytime I press the "ESC" key, the garbage starts, after 30 sec. the screen appear again and I can go on with navigating every menu.
But if I press ESC again the garbage appears...any idea??
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#5
I have the same screen. It is underpowered. Are you powering the screen from the pi, so you can have touch screen? The pi doesn't have enough juice, and eventually you will burn it out. It just has enough to run with out kodi, once you start it, just garbage. Try powering the screen separately. A powered hub is the answer to have touch screen and enough juice.
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#6
I tried with an external power supply (I used a mouse) that I use to power a B+ (it's a Kodi media center for my TV) but nothing changed.
I will try with a powered USB hub anyway.
Thanks, regards.

Roberto
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#7
I just tried with a powered USB hub (5V 5A) but nothing changed.
I don't think it's defective since I tried a whole day with RaspBIAN without problems.
I don't really know what it could be.

Roberto
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#8
If you guys still have the problem use this in config. I had the problem and by adding this it worked fine.

hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0
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#9
Hello,
I have the same screen just the next version (1024x600) and I have the exact same problem.
Rasbpian no problems, but as soon as I start kodi (from inside X or standalone or osmc) a white screen apperas.
If I wait a little bit, the menu appears, and the white screen appears again if I touch something....
Those settings
Code:
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0

Did not work for me at all even booting has everything messed up....
I have the same just the resolution changed:
Code:
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 1024 600 60 6 0 0 0

Got from:
Code:
[email protected]:/home/osmc# /opt/vc/bin/tvservice -m DMT
Group DMT has 2 modes:
           mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive
  (prefer) mode 87: 1024x600 @ 60Hz 15:9, clock:49MHz progressive
[email protected]:/home/osmc#

Any ideas......
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#10
(2015-12-09, 22:50)cherva Wrote: Any ideas......

Does hdmi_force_mode=1 help?
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#11
Nope....
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#12
Maybe it is something with the refresh rate of kodi.......
I tried every possible os for the pi except openelec.
All work perfectly fine but as soon as I run kodi the dispaly goes out of range or something.
And then to return to X I have to Ctrl+Alt+F1 and then back to F6 ...... I will look around the xml configs and try to force 60 Hz or something...
Else I will have to choose a different approach to using it as a car radio replacement....
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#13
Report output of "tvservice -s" when lcd is working and when Kodi is running. That may show the difference.
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#14
It does not change sitting at:
state 0x12001a [HDMI DMT (87) RGB full 15:9], 1024x600 @ 60.00Hz, progressive


The black screen after quitting kodi can be reproduced by switching the resolution like this:
[email protected]:/home/pi# tvservice -m DMT
Group DMT has 2 modes:
mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive
(prefer) mode 87: 1024x600 @ 60Hz 15:9, clock:49MHz progressive
[email protected]:/home/pi# tvservice -e "DMT 4"
Powering on HDMI with explicit settings (DMT mode 4)
[email protected]:/home/pi# tvservice -e "DMT 87"
Powering on HDMI with explicit settings (DMT mode 87)

And if I try force it while kodi is running with tvservice -e "DMT 87", there is no change at all.
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#15
Is the problem a black screen when starting or stopping kodi?

Changing hdmi mode will blank the screen.
You can't do that when kodi is running - you will get a blank screen (whether using hdmi or kodi).

Are you using wheezy/jessie? How did you install kodi?
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Problem with an HDMI 7 inch LCD (Waveshare)51