tear-free screen on latest Debian image

[spin]

I am using latest Debian image with Mali drivers. I installed rootfs on microsd and also on a 60 Gb SSD

In Xorg.0.log file I get a message about tear-free screen. I have bottom part of my 10" LCD flickering.
So I have created a uEnv.txt file with sunxi_fb_mem_reserve=24 (but also 16 or 32) and modified script.bin file for defining fb0_framebuffer_num=3 as suggested in log message.

No change in screen flickering. This is more intense when there is a pop-up message (as when a download is complete) or at panel level. There is CPU monitor in panel, ad per default for LXDE in latest Debian image

Using previous image, without mail driver and with XFCE4, no flickering at all.

How can I remove this annoying effect?

Regards

Franco Spinelli

[zokl]

Hi,

Try to use a shorter cable between board and lcd. I had the same problem and it helped me.

[spin]

I am using Olimex 15 cm cable. I can reduce it to 112-13 cm but this cable is needed for the case I am building for using A20-Olinuxino on my sail boat.

Flickering i present when CPU usage go high or when there is some pop-up window in screen.

Reproducing problem is easy:

start any graphing program (midori as example), pop-up a window (setup for midori) and you have flickering

Regards

Franco Spinelli

[dlombardo]

Hi Franco,

Did you find optimal solution?


I have tested several lengths of 40 pin cable (self-made) with the latest official Debian SD image.

With 20 cm cable, Touch screen is not usable (it works, but poorly). Tearing and flickering is present.
With 15 cm cable Touch screen works, but display is jumpy from time to time, flickering and tearing with some popups.
With 10 cm cable seems like Franco described.
With 5 cm cable the picture is quite ok, a few (1-3) lines at the bottom flickering. Occasionally picture tearing with some popups - e.g. No network present at startup.

When reading older posts I ask:

1. Is it worth a hassle with the PWM to reduce the brightness?
[SOLVED] Flickering 10 inch LCD - https://www.olimex.com/forum/index.php?topic=2126.0

Although the brightness setting was already set at the middle setting, turning it down just a little bit stabilized the LCD image.

Specially, as the screen is not very bright in the first place.

2. Using settings from the older Debian image?
[RESOLVED] A10-LCD10″TS chatter
https://www.olimex.com/forum/index.php?topic=1916.0

Re: A10-LCD10″TS chatter
« Reply #3 on: September 26, 2013, 10:52:51 AM »
Yesterday I noticed the same problem.
I resolved by copiyng the proper script.bin from debian r2 image, but it's better do after modifyng the uart6 & uart7 entry in the fex and generate a new bin.
Here the script.bin
https://www.amazon.it/clouddrive/share?s=NwX9iwrcST8g7_qCUEf0z4

I guess, it is best to try with option 2.

Franco, what image did you use?

[dave-at-axon]

See the postings here. The fault as found by Marc is the dotclk runs next to VSYNC and as this is running at 33Mhz (7" LCD) it affects the signal integrity of the VSYNC. Marc has done some tests on this and can see the affect. It gets worse with the 10" panel due to the higher speed.

https://www.olimex.com/forum/index.php?topic=3052.0

A shorter cable does work for 7" panels.

I am working on a drop in replacement connection that will bring the signals out to LVDS and convert back to RGB at the LCD. The 2 boards will plug into the existing connectors. I'll post this design up once I have it tested and working. I'll be using a 30 way FPC cable of up to 200mm as a test. I don't use the resistive touch but I have an LCD here I can do a test with.

[dlombardo]

Thanks. I did miss the recent updates on https://www.olimex.com/forum/index.php?topic=3052.0

So, it means it is not worth testing by changing software settings ?

[Marc Coussement]

Hi,

For your information on my 10 inch the flickering can change depending on screen contend.

I didn't check the timing at this time, but i detected a Vsync signal disturbed by Dotclk.

It is not a bad idea to verify the LCD signal timing  using a oscilloscope, but by improving the Vsync signal quality the Vertical flickering problem is solved.

At this time I am struggling with Mono implementation on A20. So LCD timing is not my major concern at this time.

Marc,

[dlombardo]

I have updated https://www.olimex.com/forum/index.php?topic=3052.0

SOLUTION:
Boot A20 Debian release 7 (current wiki linked) image on a card with HDMI monitor (and USB keyboard /w mouse for convenience)
Change the lcd_io_cfg0 from 0 to 268435456 setting for the LCD 10" in /root/change_display_a20_OlinuXino.sh
(I find it cleanly writen using switch/case syntax  )
and rerun /root/change_display_a20_OlinuXino.sh

Code Select Expand


sudo vi /root/change_display_a20_OlinuXino.sh
sudo /root/change_display_a20_OlinuXino.sh