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Old 03-18-2013, 03:55 PM   #1
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LCD panel not the same as VGA

I am running the Debian distribution on a Manx PC104 embedded board. The board has a normal VGA video output that I have connected to a monitor and this works fine.

It also has an LVDS Panel Display output which is reported to be logically the same as the VGA. When I connect an LCD panel to this port here's what happens.

1) I see the Linux Penquin logo and the initial start text on both the VGA and LCD panel. So the hardware interface is working.

2) The system switches to a default wallpaper background. (I assume it has entered some graphics processing instead of text.) I continue to see the upper left quadrant of the picture on the LCD while the full screen is display on the VGA

3. Both screens blank except for a waiting icon on the VGA.

4 The VGA display goes to the final desktop with a Task bar on the bottom and, as it turns out, the browser covering most of screen. However the panel still remains blank.

5. When I shutdown the system. VGA graphics is replaced by the console text showing the final shutdown process. At this point, the panel comes alive again and shows a quadrant of the VGA screen.

My questions are:

1. How do I get the panel to remain active through the main graphics portion?

2. How do I adjust the system so the the panel show the entire display?

3. In short, how do I get the panel to mimic the VGA?
Old 04-25-2013, 03:32 PM   #2
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You want to mimic iow have 2 identical screens show up across both monitors? Or "extended" view with 1 monitor on the left, for instance, and the other on the right?

Have you tried using xrandr?

$ xrandr --output LVDS --below VGA

Will display the X output of LVDS "geographically below" the VGA X output. Use "xrandr --help" or "man xrandr" for more settings.
If the chip is nVidia, you could probably do this with the proprietary driver as well.
Old 04-25-2013, 03:53 PM   #3
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Not displaying the full screen or blanking out on LCDs usually is caused by wrong settings for resolution and/or refresh rate. Try to set the correct settings for the LCD.
Old 04-25-2013, 05:10 PM   #4
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My problem was caused by a faulty setting in the CMOS EEPROM. The LCD was not enabled which is why it worked only part of the time. It certainly wasn't enabled with a resolution corresponding to the actual LCD,hence the truncated display.


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