[Arm-netbook] 480 × 272 5" LCD lash up ready for testing

[joem]

On Thu, 2013-09-12 at 10:09 +0000, joem wrote:
> Hi,
> 
> A 480 × 272 5" LCD which costs <$15 has been lashed up for testing:
> 
> http://www.gplsquared.com/eoma_boot/eoma_boot.html#lcd_lashup
> 
> The LCD is a KD43G18-40NB-A1.
> Aliexpress store sell these LCDs
> http://www.aliexpress.com/wholesale?SearchText=KD43G18-40NB-A1
> 
> Datasheet http://www.gplsquared.com/eoma_boot/KD43G18-40NB-A1-1.pdf 
> 
> Anyone got a time to do a time saving uSD image
> configured for 480 x 272 operation that I can try for
> a bit of quick verification :) ?


The LCD was wired up with 3.3V and 18V + 100R in series
for the back light last night.

Notice one problem straight away.
That particular model of LCD requires a DEN signal
The DEN or Display ENable signal informs the LCD
to ignore the data on the IO lines while the CPU
is booting, or when the video bus is doing
something unrelated to video. There is no DEN signal from
the MEB, so I left it fully on by tying it to
3.3V through a 1K resistor.

The consequence of doing that was the display
would show a lot of agonising interference lines until
the CPU has booted and set up the IO lines.

If the EOMA has spare pins, I recommend adding a DEN line
from EOMA to make LCDs more easier to use.
As a temporary solution,
may be a gpio line could be persuaded to become the DEN line
by modifying script.fex.

VGA displays are usually OK on not needing a DEN signal
because the picture won't light up until monitor
receives good number of correct vertical sync signals.


At the moment the LCD is not being initialised properly.
The boot log is here
http://www.gplsquared.com/eoma_boot/lcd_boot_log.txt
The script.fex used is here
http://www.gplsquared.com/eoma_boot/script.fex

Any help appreciated.