MonJovi

Another observation with my TX.
There are times that when I quick-tap a menu item, the next item either above or below (mostly below) responds instead. Using a digitizer tool, "digitest", it shows that the digitizer is properly calibrated, only that if I tap it (too) quickly, the point of contact jumps about 2 to 3 millimeters away usually in a downward direction.
Does this happen to your TX? Could this be a digitizer problem?

userwaldo

Try recal. There are a number of calibration programs out there but I've found recal to be pretty good and high resolution support was just added.

http://www.freewarepalm.com/utilities/recal.shtml

dmitrygr

never happened to me, but if it REALLY bothers you, get an over/under clocking app and significantly lower the speed. For example BUS: 91, CPU: 136. Will save you some battery as well

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thenightfly42

I think I see that as well - usually while playing a Minesweeper clone. I'll see if that calibrator referenced above helps.

pgenie

Its alright 2mm -- There is no problem at all...

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Thornburgh

I've seen this issue on several TXs, especially in the graffiti area after about a month's use.

The digitizer seems to become less sensitive, so that simply sliding the pen over the graffiti area no longer registers (think felt tip pressure) -- you must push down (more like a pencil). At the same time, the digitizer starts to register false strokes. Quick dots are regularly perceived as diagonal lines, for example, or letters have a diagonal line appended to them when you lift up. You can see this effect because of the visual feedback in the graffiti area on the TX.

Also if you repeatedly tap the same spot in the the graffiti area, you can see that some of the dots register several millimeters away from the spot tapped. You can also record this effect using the notepad program full screen.

Recalibrating has no effect on this.

I exchanged my first TX because of this problem, but the replacement developed the same problem after about a month.

I think it's just a design flaw in the digitizer. I also wonder whether it affected my older palms too. They didn't have the visual feedback for graffiti, so I don't know, but it might explain why I've always had graffiti errors. You really have to write large characters, slowly and with firm pressure, to avoid this.

_Em

I've had this problem off and on; I've always found that it goes away after a hard reset and then slowly creeps back. I just tried DigiE from the T3 thread, and it seems to have fixed the issue! So now I'll just keep that little app on my SD card and use it when the screen goes sloppy on me next.

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pruss

How do you use DigiE? I just get resets after every tap on my TX.

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_Em

Strange; I keep it in my Launcher folder, and run it from there. Launch the app, tap where the lines intersect, and when it's done, the digitizer is back to normal and you're back in the default applications launcher.

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pruss

Oh, it just sets the callibration. No, it's not going to fix the jitter, I think.

I found a developer side fix for half the jitter--the pen down jitter. You just ignore the sample in the event structure on the penDownEvent and replace it with the next sample you grab yourself from HALPenPosition() (an ARM-only function). There is no pen movement jitter, but I still have no cure for the pen-up jitter.

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pruss

I lowered the speed to the minimum of 26MHz, and the problem persists.

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willbewill

DigiE caused problems on my TX with Mini Keyboard and others - seemed to calibrate to wrong places, had to remove and soft reset to put it right again.

pruss

I did a lot of experimenting this morning, logging a couple of megabytes of pen data and looking at it. The jitter happens at the end of a stroke, more often when the stroke is just a tap. What happens is that the last two (on my TX) or three (on my T5) digitizer samples before the pen-up condition is detected are faulty--maybe even VERY faulty. We're talking about a 5ms period of time at the end of the stroke here.

I am guessing that what is happening is that while the pen is being lifted up, the touch screen uncompresses in a way that causes a false reading. If at that very point the digitizer detected the pen up, then everything would be fine. But it only detects the pen up AFTER giving the false readings. Hence the problem.

I was able to reduce the incidence of this problem in AtomikKeyboard by an order of magnitude simply by discarding the last five samples before a penUp event. Interestingly, this did not significantly impact sensitivity--people do not move the pen that fast.

This issue has nothing to do with callibration, I am pretty sure.

It might be possible to write a little hack that fixes this. I don't know. For now I will live with the AtomikKeyboard-specific solution, and see how well that works.

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maceyr

Check out my Palm blog posting on digitizers and see if anything helps.