lcd display image in different offset

[rans]

Hello,

I have configured a 240x320 LCD with timing correcpond to 240 pixel line and 512 lines (instead of 320). Any other configuration did not work with my LCD.

Now I can finally get a stable image , but each time the image starts at different line (and the rest of the screen is blank).

on doing:

dd if=/dev/zero of=/dev/fb0

It resolved this issue.

Does anyone anyone knows why the above command resolve the problem ? I would assume that framebuffer content is the same even before doing this command, so i don't understand the effect.

I also do not understand what the reason for the different line offset in the first place.

Thanks,

Ran

[Yuri]

Hello,

Looks like the LCD was not fully correctly in initialized.

Please look at app note  AN3974 “Different Display Configurations on

i.MX35 Linux PDK” describing display parameters for initialization.

http://cache.freescale.com/files/dsp/doc/app_note/AN3974.pdf

Have a great day,
Yuri

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[rans]

Hi Yuri,

Thank you for the suggestion and link.

But why did the following command seems to redsolved the issue

dd if=/dev/zero of=/dev/fb0

What effect does it have, and does it imply that the timing are correct ?

Regards,

Ran

[rans]

Hi,

I wanted to add that framebuffer is configured as following:

fbset -fb /dev/fb0 -xres 240 -yres 320 -vxres 240 -vyres 320

so, I don't know why

dd if=/dev/zero of=/dev/fb0

results in image correct display starting with line 0 on the screen.

I think that writing to framebuffer should fill the complete buffer.

Regards,

Ran

[Yuri]

Hello,

I do not think, that clearing frame buffer fully resolve the issue, if timings are

not correct.

Regards,
Yuri.