LCD screen turns white

Hi,

I have a problem with a new mini2440 S3C2440 ARM9 Board with 3.5" TFT LCD
Touch Screen. It appears almost completely white when I turn on the device!
If I tilt the screen, I can see a faint image of bootloader and  Qutopia
interface. Touch functions all work ok, I can launch apps, etc. Here is the
pictures of what it looks like:
http://www.badscience.ru/images/4.jpg
http://www.badscience.ru/images/3.jpg

I only attached a screen and power adapter, didn't change anything at all.
I also checked all LCD connections and didn't find any problems.

Is it some configuration must be done? I didn't find anything about such
behavior in manual.

Seems to be a contrast problem with the display...

maybe it is a problem of broken wire

So, it's definitely a hardware problem, am I correct?
I don't see any broken wires or some other damaged components.

Hi,

maybe the connector cable is incompact

regards

mindee

May be due to poor contact of the connector. 
Try unplug the LCD connector and then reconnect.
Good luck to you.

Thanks for your answers!
Connectors and cables look good to me, but I'll try to get another cable
for a test.

I head the same problem. The power cords ware 1m long and very thin, so the
voltage drop at 1A was more than 1V! So even when power supply was giving
5V the voltage at the board was 4V witch is not enough.

Quite sure it's connector, sometimes happens with me, worse when I move the
board. If I dont touch it, stays on for hours.

When I finally figured out the right DC power connector to buy I found that
I had to buy two different manufacturers representations of the mechanical
dimensions in order to get one type that would not be intermittent.

Hello!

Anyone solve the problem? I've got 5 Mini boards and white-screen problem
appears on each one. Sometimes screen goes white after 2-3 days sometimes
is a couple of minutes. There are two ways to fix it - turn off the board
or disconnect LCD cable, but it's very irritating. Can I do anything else?

best regards
Tom

We have a similar problem with our product. When we set date and time to
our unit, the screen goes to white and remains there until u touch it. The
application behind it is still running. Is there any help any one can
provide here?

Thank you.

Tejas.

The reason for white screen is when the CPU is powered up it by default
configures all the GPIO as output ports and makes them high. The LCD
backlight control (PWR_EN) in the schematics is pulled high and since the
LCD is also not initialized you will see either random lines or a totally
white screen depending on the LCD you have. We fixed by inverting the
PWR_EN signal on the LCD board and by modifying the kernel (
mach_mini2440.c file ) so instead of making the GPIO high  on
initialization we explicitly pull it to ground. 

We did this for the N43i board and it works as described. 

--fatbrain

fatbrain,

I can see how you wouldn't want this unwanted feature in a consumer's
product.

So, thanks for explaining how you sorted the problem.

However, one question.  Your procedure takes care of the initialisation
process, but don't you have to do something for future accesses to the
backlight? IE, invert all backlight commands?

Dave

yes , you need to invert backlight commands for future accesses via command
line. Through code you could initialize GPIO  for inverted logic, so  your
code does  not change and the only changes are done in GPIO init. 

--fatbrain

fatbrain,

"Through code you could initialize GPIO for inverted logic"

Not having run across this capability on the ATMEL AVR series, that I have
been working with for the past 10 years nor aware of being able to do this
on the S3C24XX series I did some investigation.  The Samsung datasheet does
not appear to mention this capability. Also, looking at how one can operate
GPIO from userspace I haven't seen anything which indicates that you can
invert the logic. Could you point me to some documentation or describe in
some more detail how one can do this without modifying legacy code?

Regards,
Dave

I have written  wrapper code over sysfs for accessing GPIO , and the
wrapper code takes care of inverted logic.

Ah . . . thank you.

Dave

calibration of touch screen in  friendly arm mini 2440 w35 board getting
disturbed everytime the board is switched on. i m recalibrating it but no
effect. Please suggest some measures.

Thank You

After you have calibrated the screen you should find a /etc/pointercal
file.  When you turn it off does it disappear?

If it does, show me your /etc/init.d/rcS file