steinerlein
Posts: 18
Joined: Thu Mar 21, 2013 4:59 pm

framebuffer size, overscan and native resolution

Fri Dec 14, 2018 11:50 am

Hi all,

I am currently setting up a custom TFT display over DPI and have gotten the timings to work well so far. Now I am struggling to get the framebuffer size set correctly.
The display I am using displays a resolution of 800x320 but the display controller takes a resolution of 800x480 and cuts off the remaining lines.
Thus, my config.txt looks like this:

Code: Select all

dtparam=audio=on
enable_uart=0

dtparam=spi=off
dtparam=i2c_arm=off

dpi_group=2
dpi_mode=87

enable_dpi_lcd=1
display_default_lcd=1

framebuffer_width=800
framebuffer_height=480

display_rotate=0x10002

dpi_output_format=0x3F4016
dpi_timings=800 0 210 1 46 480 0 22 1 23 0 0 0 60 0 33000000 7

As you can see, I have the framebuffer height set to 480px as well. Everything is displayed at the native resolution in both axis, but the framebuffer goes "off screen". If I set it to the displayed height of 320px I can see everything, but the image is compressed vertically. In this case I also set overscan_bottom to 160.

What am really looking for would be a margin for the framebuffer, so that I can set the native resolution of 480px and tell it to ignore the bottom 160 lines.

Is there such a thing?
Attachments
photo_2018-12-14_12-54-54.geaendert.jpg
framebuffer_height=320 and overscan_bottom=160
photo_2018-12-14_12-54-54.geaendert.jpg (236.85 KiB) Viewed 426 times
photo_2018-12-14_12-54-49.geaendert.jpg
framebuffer_heigt=480
photo_2018-12-14_12-54-49.geaendert.jpg (158.52 KiB) Viewed 426 times

aBUGSworstnightmare
Posts: 1508
Joined: Tue Jun 30, 2015 1:35 pm

Re: framebuffer size, overscan and native resolution

Fri Dec 14, 2018 7:35 pm

What do you expect to be the result of display_rotate in your config?

Are you sure your timimg is right? How does this 'lcd controller' deal with (I expect bottom) remaining lines? Why do you need to add overscan bottom at all?

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