Fix black screen blinking flickering with HDMI-VGA-adapter

[Ultradrom]

    Problem:
Fullscreen black blinking-flickering on TVbox (H6: "V96 mini") with HDMI-VGA-adapter and Armbian.
10 seconds picture is ok, 5 seconds picture is black, repeat...
More affected on white images.

 

    Details:
TVbox : "V96 mini" (Allwinner H6)
HDMI-VGA-adapter : 10cm cable with small square box (with audio jack, without power)
Distro: (from Balbes150) Armbian_21.08.0-trunk_Aw-h6-tv_hirsute_current_5.10.53_xfce_desktop.img.xz
Monitor: any with resolution 1280x1024 (may be another)
No problems with direct HDMI connection, and/or under Android.

 

    Solution: (fix for example 1280x1024 @ 60hz)
In two words: change default refresh rate Hz to anoher value (for needed resolution).

 

1. Check current list of resolutions and refresh rates:
Note: current mode marked by "*".

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
HDMI-1 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 531mm x 298mm
   1920x1080     60.00 +  59.94  
   1680x1050     59.88  
   1600x900      60.00  
   1280x1024     75.02    60.02* 
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    59.94  
   1024x768      75.03    60.00  
   832x624       74.55  
   800x600       75.00    60.32  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  

 

2. Prepare for adding new mode (Calculate VESA CVT mode lines for 1280x1024 , 60hz ):
Note : some text output from last line of this command needed for next command.

$ cvt 1280 1024 60
# 1280x1024 59.89 Hz (CVT 1.31M4) hsync: 63.67 kHz; pclk: 109.00 MHz
Modeline "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

 

3. Create new mode:
Before run : need to copy all text from previous command after word "Modeline",
and paste to this command after words "xrandr --newmode".

$ xrandr --newmode "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync

 

4. Add new mode:

$ xrandr --addmode HDMI-1 "1280x1024_60.00"

 

5. Check is new mode added to list:

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
HDMI-1 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 531mm x 298mm
   1920x1080     60.00 +  59.94  
   1680x1050     59.88  
   1600x900      60.00  
   1280x1024     75.02    60.02* 
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    59.94  
   1024x768      75.03    60.00  
   832x624       74.55  
   800x600       75.00    60.32  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  
   1280x1024_60.00  59.89

 

6. Switch to new mode now:

$ xrandr --output HDMI-1 --mode 1280x1024_60.00

 

7. Final check:
Note: old bad hz value is "60.02", new good hz value is "59.89"

$ xrandr
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
HDMI-1 connected primary 1280x1024+0+0 (normal left inverted right x axis y axis) 531mm x 298mm
   1920x1080     60.00 +  59.94  
   1680x1050     59.88  
   1600x900      60.00  
   1280x1024     75.02    60.02  
   1280x800      59.91  
   1152x864      75.00  
   1280x720      60.00    59.94  
   1024x768      75.03    60.00  
   832x624       74.55  
   800x600       75.00    60.32  
   720x480       60.00    59.94  
   640x480       75.00    60.00    59.94  
   720x400       70.08  
   1280x1024_60.00  59.89* 

 

8. If it works as expected, save new mode permanently (work after reboot).
Add it to Xorg config by editing or creating file "/etc/X11/xorg.conf.d/40-monitor.conf":

Section "Monitor"
Identifier "HDMI-1"
Modeline "1280x1024_60.00"  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync
Option "PreferredMode" "1280x1024"
EndSection

 

9. Reboot

 

? 10. Check settings in your GUI (for XFCE : Settings / Display ) :
? 1280x1024*
? 59.9hz
? Apply, Reboot