QVGA for Neo
laforge at openmoko.org
Thu Oct 4 15:20:22 CEST 2007
Hi, sorry for my delayed response.
On Thu, Sep 27, 2007 at 06:42:47AM -0700, john cass wrote:
> I have been playing with QVGA mode for the Neo and have some observations and
> questions. QVGA will be important for several key Neo applications including
> games and movie playing. It may also offer lower power usage.
yes, we've always wanted QVGA support, but with all the higher priority
> The LCM register set is not documented but a patch was made by Stefan Schmidt
> which demonstrated switching it into QVGA mode.(patch for /drivers/spi/jbt6k74.c)
> Basically this patch changes two register values called DISPLAY_MODE and
> QUAD_RATE, it also fills in timing values to an alternate set of registers
> for vga or qvga.
> This patch does not change the framebuffer driver (within the s3c2410 -
> /drivers/video/s3c2410fb.c) which by default is set up to always generate a
> VGA signal.
I thought Stefan was never able to finish his QVGA patch ?!?
Anyway, what a pleasant surprise.
In QVGA mode, the LCM needs the following minimal timings:
vertical cycle 326 line
vertical data start 4 line
verical sync pulse 2 line
vertical front porch 2 line
vertical back porch 2 line
vertical blanking period 6 line
vertical active area 320 line
horizontal cycle 344 dot
horizontal front porch 88 dot
horizontal fsync pulse 8 dot
horizontal back porch 8 dot
horizontal data start 16 dot
horizontal active area 240 dot
clock frequency 6.5 MHz
So once the LCM has been switched to QVGA using jbt6k74, the s3c2410_fb
needs to be re-programmed to generate a signal according to the
> 1) Does qvga mode in the LCM require/expect a vga signal, or can it run from a
> qvga signal?
QVGA signal accordign to specs above.
> As it stands, we can see qvga on the screen but linux (console, X) still
> thinks it has a 480x640 framebuffer (which it does!) and I cant see a way
> of forcing it to use only a part of that.
> It is relatively straightforward to change the framebuffer (and console, X) to
> generate a qvga signal using fbset but will the LCM accept that?
- Harald Welte <laforge at openmoko.org> http://openmoko.org/
Software for the world's first truly open Free Software mobile phone
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