Olimex Support Forum

OLinuXino Android / Linux boards and System On Modules => A20 => Topic started by: mushketer888 on November 08, 2014, 02:25:46 PM

Title: Screen flickering only with X11 Desktop manager
Post by: mushketer888 on November 08, 2014, 02:25:46 PM
Strange but LCD screen is flickering only with X11 and some dekstop manager
For example x-screensaver doesnt flicker at all!
And terminal also (ctrl-f1 etc)
What can be the cause?
Title: Re: Screen flickering only with X11 Desktop manager
Post by: mushketer888 on November 08, 2014, 03:47:46 PM
Very strange
I edited fex to

lcd_io_cfg0 = 268435456

and all worked well
Title: Re: Screen flickering only with X11 Desktop manager
Post by: martinayotte on November 08, 2014, 04:21:52 PM
Effectively !
I've recently upgraded to A20-Debian-release8 (I was using rel4), and I had to tweak lcd_io_cfg0 again.
I don't know why this old issue isn't fixed forever in newer releases.
Title: Re: Screen flickering only with X11 Desktop manager
Post by: rouvas on November 08, 2014, 04:55:43 PM
Where was that value you edited? In some config file?
Title: Re: Screen flickering only with X11 Desktop manager
Post by: JohnS on November 08, 2014, 05:13:22 PM
Each of you - which LCD are you using?

John
Title: Re: Screen flickering only with X11 Desktop manager
Post by: rouvas on November 08, 2014, 06:16:46 PM
I am using A13-LCD10TS. To be honest, I haven't observed any flickering, but then I'm not loading LXDE either. I stop at openbox.
Title: Re: Screen flickering only with X11 Desktop manager
Post by: martinayotte on November 09, 2014, 03:40:53 PM
I'm using both LCD10TS and LCD7TS and I was facing the this flickering issue since the beginning until last June, when I discovered a thread where someone find a fix using lcd_io_cfg0 = 268435456 in FEX file, I've apply this fix and since then, I don't have the issue anymore.
The flickering was intermittent depending of the contrast of the background images used in my application.
I think this fix should be permanent in /root/change_display_a20_olimex.sh but it isn't there yet.
Title: Re: Screen flickering only with X11 Desktop manager
Post by: dave-at-axon on November 10, 2014, 01:56:14 AM
That value is hex 0x10000000 and sets bit 28 of the TCON0_IO_POL_REG to 1 and I mentioned this here before:

https://www.olimex.com/forum/index.php?topic=2933.msg13211#msg13211

Still not found out what it changes as limited documentation.
Title: Re: Screen flickering only with X11 Desktop manager
Post by: JohnS on November 10, 2014, 10:15:58 AM
Thanks, everyone.

If it's changing a phase then a 'scope, data sheets and some work ought to reveal it.

Or just set it and when it works move on :)

John (who doesn't even own the LCD or have the skills to use the 'scope if I did!)
Title: Re: Screen flickering only with X11 Desktop manager
Post by: dave-at-axon on November 10, 2014, 02:42:05 PM
I'd like to check what is does so I plan to hook up a logic analyser when I get a little time to play with it and then try the different settings.

I just tried out a Newhaven 7" LCD today and although it did display without any timing changes, there is a little bit of an issue that I think can be sorted though timing changes.