Imprecise Touchscreen

[Meromaru]

When touching the screen, the pointer trembles around a radius of 2 pixels. I already tried calibrating 3+ times in sequence, using a NDS stylus, taking out the screen protector, everything to no avail. Does anyone else have this problem? It's been like this since the first day I got my Wiz (only a few weeks ago).
Firmware version is 1.2.6.

 

[kasi]

Hi Memoramu,

This might be "normal". My WIZ is of the fist batch, still FW 1.1.0. I just re-checked it with touchscreen-test. It's always trembling.

There is a lot of threads and posts regarding the touchscreen. If you consider some of these posts a 2-pixel radius is quite ok.
It seems we just have to live with it. However, I got quite good results at Animagic using the touchscreen.
In some game types I even made it (and stayed) into the top ten vs. my wife using the d-pad.
But THIS is not an issue of the touch screen and not even of myself.

 

[Meromaru]

Seems like a common issue after all. Too bad.

Yeah, I looked up for related posts, but the most I read was about accuracy problems, not so much about the trembling, though.

Still, even a 2-pixel difference is enough for having a hard time in Exult trying to click something instead of dragging ("TOO HEAVY" - damn!).

(btw, good luck for your wife next time! =)

 

[senquack]

I spent a lot of time trying to improve the GP2X's noisy and jumpy touchscreen, but not on the Wiz (yet, anyway) so I can give some limited advice or maybe insight:

This may or may not apply to the Wiz as well: the accuracy of the GP2X touchscreen was extremely bad unless you ignored reported samples with a pressure value of less than 35,000 or something like that. Anything lower and it was likely noise, of which there was a lot that occured when the stylus was lifted from the touchpad. Often the cursor would leap elsewhere entirely! It is interesting it ever reported different pressure values, as it and the Wiz are just simple non-pressure-sensitive pads.

One thing I noticed on the GP2X was that the touchscreen was much more pleasant to use when you only used the stylus for controlling the cursor but an actual button click came from pressing one of the GP2X's buttons. Much more sensible, because it is much nicer to use for programs that have GUIs with small icons. Tap-to-click sucks for these, there's no way to have better than I'd say maybe 90% accuracy on what icons and widgets you are pressing. The button-for-click method allows tapping in the general region you intend, letting go, and examining exactly where the ole' cursor lies so you can follow up with either a button-press (mapped to mouse click) or quick correction with your stylus and then a button press. Maximum accuracy is achieved when holding the stylus down while pressing the button.

Regarding the noise it was always largest in one axis, I believe the horizontal one. I spent a week hacking tslib to have a brand-new 15-sample buffer that filtered the noise quite effectively, while still detecting rapid movements and switching to low-lag high-noise mode for those brief times, flushing the buffer when fast motion is detected. In case anyone wants to look, it's here in the svn

 

[Meromaru]

Thanks a lot, Senor Quack. I'm taking a look at the code.

I also found out you already discussed it here:
http://www.gp32x.de/board/index.php?/topic/52849-touchscreen-jitter-filter/page__view__findpost__p__836469

 

[senquack]

Thanks a lot, Senor Quack. I'm taking a look at the code.

I also found out you already discussed it here:
http://www.gp32x.de/board/index.php?/topic/52849-touchscreen-jitter-filter/page__view__findpost__p__836469

Oh, BTW I am planning on really doing a great job of making a good Exult port that has the best touchscreen and controsl as possible.. hopefully will make this my next project soon.

 

[Darkknight512]

Quack do you know if Win2X uses your version of tslib? I haven't notices the touch screen even shake a bit, the lines I can draw on the test program are incredibly accurate, so accurate that I believed (and still do) that the Wiz has the most accurate touch screen I have ever used.

 

[Meromaru]

At least in my Wiz, Win2X doesn't improve the precision of the touchscreen.

 

[senquack]

Quack do you know if Win2X uses your version of tslib? I haven't notices the touch screen even shake a bit, the lines I can draw on the test program are incredibly accurate, so accurate that I believed (and still do) that the Wiz has the most accurate touch screen I have ever used.

No, I don't know.. Honestly, my Wiz's touchscreen is quite a bit more accurate in all apps than the GP2X's ever was. A jitter of 1 or 2pixels, especially in only one axis, is pretty impressive compared to the GP2X' wildly noisy and somtimes 10-pixel radius jitter. Ultimately, a touchscreen smoother for the Wiz wasn't even necessary for my port of OpenTTD, which has an extremely intricate GUI. I can play it just fine, and it works about as well unfiltered as the GP2X did with my filter.

Do others here think that their Wiz is more noisy than what I am describing with mine? 1-2 pixel jitter or is it significantly more and is it on one axis or both?