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Full Version: SL-C860 stylus-digitizer weirdness
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dfnr2
I just got a C860 with Cacko-1.21a rom. After a while in use, the digitizer develops "jitter" about 1cm about the touch-point along the long axis. This is severe enough to make the system unusable--wrong icons are selected, etc. In the handwriting window, touching the screen with the stylus produces a line in the long axis of the screen, about 1cm long, centered at the stylus. Moving the stylus in the short-axis dimension produces a zig-zag pattern. Rebooting the system restores the normal behavior.


My first thought was flaky hardware, but since reboot fixes it, I wonder if it could be a driver bug. Has anyone else with a c860 or c7X0 seen the problem?

Thanks,

Dave
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If you've been playing with the overclocking , you'll find that power saving settings (ie normal and below on c750/760) produce some weird stylus effects......this could be your problem.

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dfnr2
Bingo! That's exactly it. Thanks
dwchapin
This is odd...

I experienced this jitter along the long axis for the first time this morning, after doing pretty much what I do every morning -- swapping the bluetooth CF card out for the WiFi, doing various synchronizations with my home machine (KOPI, sitescooper files, etc) and then putting the bluetooth card (Socket G) back in.

Next thing I know I'm making a note in FreeNote/Qt and the lines are super-jittery.

Weird thing is that I've never ever moved the clocking on my 860 from where Cacko defaults it ("Default (PXA250)"). I'd never heard of this jitter problem so after a brief moment of panic I played with various levels of resort (reboot, power off and remove battery, etc) which did not fix the problem.

One thing I *did* notice though was that the jitter went from the occasional blip (drawing a straight line has one or two jaggies) to a chaotic mess (attempt to draw a straight line produces a 1-cm wide path of scribbles) when I had the bluetooth card in. Perhaps the Socket G is putting the Z in some sort of powersave mode that exposes the bug?

Odd thing is I've been using the Z with this exact configuration for some time (on Cacko 1.21a and 1.22 since it's release) without incident, and AFAICT I didn't do/change/install anything else that would cause this to suddenly start happening.

Now that I've switched the clocking to "Normal" ("Overclocked" works as well) everything is fine, but when I go back to Default (PXA250) or "Power Saving" I get jitter, and now it happens whether or not the bluetooth card is inserted. The only stable modes seem to be 'Normal', "Default (PXA255)" and "Overclocked".
kahm
QUOTE(dwchapin @ Jan 24 2005, 05:05 PM)
This is odd...

I experienced this jitter along the long axis for the first time this morning, after doing pretty much what I do every morning -- swapping the bluetooth CF card out for the WiFi, doing various synchronizations with my home machine (KOPI, sitescooper files, etc) and then putting the bluetooth card (Socket G) back in.

Next thing I know I'm making a note in FreeNote/Qt and the lines are super-jittery.

Weird thing is that I've never ever moved the clocking on my 860 from where Cacko defaults it ("Default (PXA250)").  I'd never heard of this jitter problem so after a brief moment of panic  I played with various levels of resort (reboot, power off and remove battery, etc) which did not fix the problem.

One thing I *did* notice though was that the jitter went from the occasional blip (drawing a straight line has one or two jaggies) to a chaotic mess (attempt to draw a straight line produces a 1-cm wide path of scribbles) when I had the bluetooth card in.  Perhaps the Socket G is putting the Z in some sort of powersave mode that exposes the bug?

Odd thing is I've been using the Z with this exact configuration for some time (on Cacko 1.21a and 1.22 since it's release) without incident, and AFAICT I didn't do/change/install anything else that would cause this to suddenly start happening.

Now that I've switched the clocking to "Normal" ("Overclocked" works as well) everything is fine, but when I go back to Default (PXA250) or "Power Saving" I get jitter, and now it happens whether or not the bluetooth card is inserted.  The only stable modes seem to be 'Normal', "Default (PXA255)" and "Overclocked".
*



That is because you're 860 is a PXA255, not a 250. I believe the SL-C700 is the only one of the C series with a PXA250 chip. If you run it at on the Default PXA250 you're underclocking the Z.
dwchapin
QUOTE
That is because you're 860 is a PXA255, not a 250. I believe the SL-C700 is the only one of the C series with a PXA250 chip. If you run it at on the Default PXA250 you're underclocking the Z.


Aha. This is the problem then: I don't think I ever knew what type of processor I had; all I knew was that I had never changed the clocking. I was therefore assuming that since I'd never changed it, it was at the default.

So here is the problem: even after I change the clocking to PXA255, every once in a while (usu. after a suspend-resume) it reverts back to a PXA250. I get this about once/day (may be happening more but it's only really noticeable in FreeNote, so I discover it only when I need to doodle). This has to be some sort of bug...
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