Re: [H2200-port] Re: Fwd: Unstable pointing?

Hello Vladimir,

Monday, June 19, 2006, 1:50:38 PM, you wrote:

> Hi,

> I've seen the same thing on my h2200. Sometimes pointer jumps to the top of
> the screen. It makes handwriting recognition unusable. Sometimes when I'm
> pressing a button in the GUI opie ignores it and I need to press twice.

> Strange, but in GPE touchscreen works quite better. I've thought that GPE
> and OPIE uses the same tslib, don't they ?

> And even in GPE there is some jitter with touchscreen: when I drag scrollbar
> and stop to move my stylus scrollbar positions still oscillates around
> stylus. There is no such effect in WinCE.

  Yes, those are all effects of drivers written not up to specs. On
the example of h4000_ts evolution (tracking h1910_ts):

1. Once it just read the first sample from ADC after interrupt -
diplsaying all those horrible "linearity" problems.
2. Then it was brought a little to specs: there're few samples taken
each time (on initial pen IRQ or on subequent timter IRQs). First N
are thrown away (N=1 apparently works good enough). The rest are
bounded - i.e., all samples are checked to be close (within 8 units,
IIRC), and if not, thrown away as not stabel reading. Well, outcome of
this all machinery unfortunately is one random sample (like, first,
or something) taken as reading. Result - that cursor jitter which is being
described.
3. But just adhering to recommended algorithm - averaging few readings
from the step above (I tried with 3) gave me a rock-solid cursor, not
worse than in wince. (The caveat is that sometimes sursor stopped
tracking on quick moves - so, all parameters needs to be tries and
adjusted first).

  Ok, looking in h2200's driver, samcop_ts.c - it just that naive as
to take first ADC reading. Of course, SAMCOP might be doing some
dejittering on its own, but I'd rather not trust that and use
techniques as described above.

> Carl Beech wrote:

>> Ok, many thanks Erik, I'll pass this one over to the 2210 people I know -
>> and see if they have any comment....
>> 
>> Many thanks
>> 
>> Carl.
>> 
>> On 6/18/06, Erik Hovland <[email protected]>
>> wrote:
[]
>>>
>>> You might want to ask on the h2200-port list or kernel-discuss.
>>>
>>> I will say that h2200 support in Opie is a farely new thing and it might
>>> be likely that the tslib support is not quite right.
>>>
>>> But my h5550 occassionally shows glitches in Opie with the handwriting
>>> applet and the companion chip in h2200 and h5550 are very similar. So I
>>> am not surprised that you see this issue.


-- 
Best regards,
 Paul                            mailto:[email protected]

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