Problems with 7'' Display

Hello,

we tested several Mini2440, two with 3.5'' Display and 4 with 7'' Display.
We got them via E-Bay from Shanghai and Hongkong.
With the Mini2440s, we got small switching power-supplies for 5V.

The two with 3.5'' Display work perfectly, but the Mini2440 with 7''
Display make problems.

Sometimes, they don´t start, the screen remains white, sometimes, we see
the starting screen (tasman tux) for less than a second and then a white
screen and then, the system starts normaly, but may be, after some time,
some minutes or hours, the screen gets white again.

The mini2440 remains active, console output on RS232 is ok, but nothing on
the screen and no possibility, to get the screen back to normal function,
even pressing the reset button has no success. Only power off and after
some seconds on can solve it.

I already changed the power supply to another one (mean well 5V 25VA), but
the same result. We also tested several kernels and linux distributions
without better results.

Any hints or suggestions, how to solve this problem?

Today, i got 5 new devices from a distributor here in germany, but i have
not tested.

Best regards

Stefan Bröring
DF9BI

Hello Stefan,
I can only confirm the same behavior using this GPE image [1]. No problem
with the original Qtopia image.

Regards.
Clemente.


[1]
http://www.andahammer.com/Downloads/MoreFlorian/gpe-image-micro2440.jffs2

Hi, thank you for this hint.

Problem is, i am not so much involved in the whole thing and i am not the
linux or qtopia specialist. But as i understood, the colege, who installed
the image had some problems with Qtopia, so he tried qt instead. I am not
sure, which image he used, but i think, it was the original version for 7''
display from this page. But now, we need access to gpio and as a read,
access to gpio is not possible with the original image, so he installed
something called armstorm-linux.

But, we saw this behaviour with the original image from this site and also
with the armstorm-image.

So i thought, it might be a hardware problem with the 7'' display...

Best regards

Stefan DF9BI

hello stefan,

for the first time i had the same problems with this display.
the (my) displays needs a minimum of 5.14V, but the main problem
was the dc-connector and the dc-plug.

greetings
harald

hi

I had the same problem. Make sure you have really 5V and not 4.5V or 4.7V.

Hello to all,

problem was the image we used. Now with the original image, it is doing
well.

Thanks for all the hints, i will also have a look on the voltage.

Best regards

Stefan
DF9BI

My friendlyARM 7'' Display has some problems.as like yours  not Sometimes
but always the screen remains white and most important thing is that its
USB port does not recognise USB cable.if any body have the solution please
send it to my id->>'tudu_bhimsen@yahoo.com'

Try the Qtopia image from the download section. 
Here is a small guide http://www.friendlyarm.net/dl.php?file=download.pdf

Also is the LCD Power Jumper set to 5V?

I had the same problem:
- voltage from power supply drops by 0,2v on dc connecter and power switch
- it drops another 0,5v on cable connecting computer with display
- according to lcd documentation - backlight voltage should be in range
4,8-5,2v

You can solve the problem by attaching additional +5v wire directly to lcd
board.
Original 5v power supply works properly, because it has actually 5,5v.

I had exactly the same problem with my 7" display. It was going white while
working or while loading the OS. The reason appeared to be the ribbon
cable. After several re-connections tiny deformations occur at the places
where connector's pins press the cable and connection becomes loose
. 
Since I turned the ends of the cable the problem disappeared.

Of course the best solution would be a new cable. Avoid disassembling of
the connections.