N900 touch screen calibration not accurate
 

I recently got myself a N900 and found it a great phone, except for the touch screen. It seemed, even after calibrating the screen as exactly as possible, that the stylus was not accurate. I had to click links and menu buttons multiple times before they reacted. e.g. It was nearly impossible to get a flash video fullscreen (pushing the little icon in bottom right corner).

When I started using VNC I noticed that the screen was not calibrated perfectly. VNC indicates (when connected to a remote desktop) where your mouse is when you move the stylus over the screen. In my case the mouse tended too much to the left and right sides of the screen. Vertical alignment was quite good.

After some testing with the calibration tool I found that this tool is not as exact as it should be. But I found a way to get the calibration accurate:

Start the touch screen calibration, and use the stylus. It asks you to press the center of the first target.

-precisely press the bottom right edge of the ring around target 1
-precisely press the bottom left edge of the ring around target 2
-precisely press the top left edge of the ring around target 3
-precisely press the top right edge of the ring around target 4

To see if the screen is calibrated correctly I checked with VNC to see the black dot exactly onder the stylus.

By calibrating the screen this way my N900 is much more accurate, also when using fingers to control the device. It resulted in much lesser miss clicks and multiple taps to opening links, menu's, icons etc...

This post might get obsolete if the screen calibration tool is updated in a newer firmware but until then it might help you to get your N900 the way it should be !

Re: N900 touch screen calibration not accurate
 

You're talking about the outermost ring?

Yeah I noticed the same thing, especially with VNC. I carefully pressed the center of each target, but at the edges of the screen it saw the pointer as being further towards the center than it was - this made moving the scroll bars difficult.

Re: N900 touch screen calibration not accurate
 

anyone posted or seen a bug? would be useful to get it fixed :D

Re: N900 touch screen calibration not accurate
 

you must have a faulty device... mine is calibrated perfectly using the calibration tool.

edit: tested it right now again using the sketch program. perfectly calibrated...

Re: N900 touch screen calibration not accurate
 

@GameboyRMH : yes, the outer ring. I had exact the same issue as you. When pointing at the scroll bar I found the 'cursor' on my remote desktop.

I don't think my device is faulty, because it works perfect. I can't say it's a bug because I don't know of other people have this too. I think most people don't even notice (and get frustrated pressing a link 3-4 times before it opens :) ).

By testing with sketch I couldn't see a difference between normal calibration and my workaround. Both seemed to be accurate.

Re: N900 touch screen calibration not accurate
 

Thanks, I can confirm the exact same symptoms. Perfect in most of the screen, everything seems fine in Sketch, but inaccurate at the edges. I'll try your calibration method when I get home later today.

Edit: I can't try VNC right now but I calibrated with your method and everything still seems fine in Sketch. Bringing up History and the cursor in MicroB seems to be easier.

Re: N900 touch screen calibration not accurate
 

I agree that Sketch seems to be fine for me, but I don't have VNC but do feel at times especially in MicroB that it's not always detecting where I'm pressing.

Weird :confused:

Re: N900 touch screen calibration not accurate
 

okay, have now recalibrated using your method... the outer ring, right?
in sketch: no difference
time will tell if I feel a difference in the browser.

Re: N900 touch screen calibration not accurate
 

Just tried VNC, it's much better now! :D I have no problem using the scroll bars anymore. The pointer is always exactly under the stylus now.

Re: N900 touch screen calibration not accurate
 

I had this problem a while ago and the solution was to touch the targets closer to the centre of the screen to get access to the edges. Shadowjk also suggested compiling and using tscalib instead and using that helps.

http://talk.maemo.org/showthread.php?t=44373