[okl4-developer] some questions about addressing / lcd-driver of the S3C2410 gta01

[Robert Wetzel]

Dennis Gessner wrote:

> Inside the manual in section 15-17 it is said (on the upper part of the
> page), that every pixel is written in 2 bytes (what would be logical in
> a 5-6-5 16bpp coding). The LOWER part of the page says, ONE Pixel is
> coded into a 24bit-field with a lot of don't-care-values (also a 5-6-5
> coding). I tried both versions of coding and never got the result I
> would like to have. For example it looks like I only have 4 different
> values of blue, what should not be with a 5 bit blue-value.

On the page 15-17 you see the layouts for both memory and pinout, which
are two different things; as a programmer you don't need to care about
the actual pinout. Maybe the byte/half-word swap configuration is not
set properly for your hardware (see lcdc#5 register, according to the
values shown both byte and halfword swap are enabled).


> Also I tried to enable 24bpp-mode
> 
> // We want to have 24BPP, so we need to chance the lcdcon1-Register
>     lcdcon1_write(0x0000017A);
> // Change HWSWP to 0 (was 1)
>     lcdcon5_write(0x0001cf08);

After digging through the documentation and stumbling over the address
registers: Do you configure these properly as well? They need a somewhat
different config in 24bpp mode(s) to the 16bpp ones due to the different
screen/bpp sizes (i.e. framebuffer end address and page width values).
That could explain the weird repeating of your pixel data on the screen.


> Another confusing thing is, inside the manual of the S3C2410 it is
> written the lcd-controller supports 24bpp. BUT - the display itself of
> the gta01 "TD028TTEC1" only supports 262k colors (what again would mean,
> I only can use 65k colors).

That is something I honestly wouldn't worry about. It's the job of the
hardware to handle this; infact there are enough LCD screens around
which cannot handle full 24bpp even though they are used together with
24/32bpp modes.


Good luck with this thing, I hope you get it working soon :-)


Robert


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Robert Wetzel
Software Engineer

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