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Author Topic: success ** Samtiq II ** amazing images on page 6  (Read 78295 times)
Drewid
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« Reply #15 on: January 31, 2007, 12:43:43 PM »

Here's a thought. It might be worth trying the LCD rotated 180 degrees and flipping it in the screen drivers (if you can).
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Rumi
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« Reply #16 on: January 31, 2007, 12:58:28 PM »

Just tried that, no luck.  Sad
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Drewid
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« Reply #17 on: January 31, 2007, 02:53:18 PM »

Shield all the cables?
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wei803
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« Reply #18 on: January 31, 2007, 04:44:01 PM »

Looks like we're having the same problem Rumi.
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Rumi
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« Reply #19 on: January 31, 2007, 09:29:35 PM »

Drew: I tried putting all the cables away from the tablet without much improvement. I actually think that the interference is being caused by the transparent little wires which are sandwiched in the Liquid Crystal unit for carrying the signal to each pixel. I am not sure why some LCDs would cause more interference than others but then we all seem to have different tablets anyway so it is hard to compare. I might email the UC-Logic people and ask them what types of LCDs they recommend with their sensors, because they do sell modules separately. That might help in the search for better LCD's.

Wei: Yes we seem to be having the same problem (same monitor)but you have the Wacom, do you get the random clicking problem as well?
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wei803
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« Reply #20 on: February 01, 2007, 04:48:09 AM »

I get random left & right click as I mentioned on another thread whenever my pointer move near to the LCD circuit.
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Rumi
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« Reply #21 on: February 01, 2007, 08:59:03 AM »

I was very excited when I started getting something on the screen but then I  noticed the random clicking and the jittering... oh well back to the drawing board Smiley
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wei803
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« Reply #22 on: February 02, 2007, 05:55:14 AM »

Don't give up! There's still some hope.
Worse come to worse, we can keep the LCD for DIY HD projector project in the future  Grin
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Drewid
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« Reply #23 on: February 02, 2007, 07:16:40 AM »

Or mod a PC case and use it instead of a window
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Rumi
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« Reply #24 on: February 04, 2007, 08:43:01 AM »

After carrying out a lot of tests on the Samtiq and finding problems with the jittering I started to shield various parts of the unit to see if that remedied the problem. Here is the extension cable which runs from the controller to the column drivers on the LCD. I have wrapped aluminum foil around the cable and in this shot I am part way through wrapping it with electric tape:

[img width=800 ]http://www.rumi.studio2pi.com.au/gallery2/d/4515-1/shielded_controller_cable.jpg?g2_GALLERYSID=454665f3677fc0d501ec0f3bb87b9469[/img]
Here is a close up, I used a bit of the ribbon cable as earth:


It was a bit tricky to shield the row and column drivers so I decided to wrap aluminum foil around the tablet instead. This is ok in my case because the tablet reading height is 25mm and I can leave the tablet in its case.


Once I had covered all the non-active area of the tablet, I wrapped a layer of tracing paper over the top to insulate the LCD from the aluminum foil:


With these tests I decided to use the DVI input of the monitor and I think that helps, I dont have any jittering problems at all. The tablet seems to work great except when the pen is lifted off the surface to a height close to its reading limit. In this situation the tablet will sometimes register false clicks, they seem to occur close to the middle of the screen but not the same spots all the time. This is very annoying and seriously affects usability, I did a lot of tests without much success, here are some of my findings:


 
  • lower refresh rates seem to help, but not a huge difference. Min tried was 60Hz
  • shielding and moving the controller/inverter did not seem to make any difference
  • unplugging both backlights tubes didnt make much difference
  • shielding the row/ column drivers don’t seem to make much difference
  • grounding the shields on the tablet, controller cable didn’t make much difference
  • wrapping foil around the pen except the tip, disables the pen! Smiley
  • filling the background in photoshop with black made the inteference worse!



This last point indicates that it is actually the liquid crystal unit which is intefering with my tablet (wacoms may be different). To display black the LCD has to supply power to a bunch of pixels so that they stop light passing through, this voltage is interfering with the tablet.

I am very close with this project but yet so far.... everything is working except when the pen is lifted. I am wondering if UC-Logic uses a special pen for their tablet modules which is not as prone to the inteference from the LCD. Or maybe they specify to the developers what LCDs are suitable for use with their modules. I would love to get some more info about this.
In the meantime I might have to keep sliding my hand across the LCD, and not work on any thing with lots of black in it!  Wink
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wei803
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« Reply #25 on: February 04, 2007, 09:16:12 AM »

I gonna give that a try!
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Drewid
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« Reply #26 on: February 04, 2007, 02:37:39 PM »

Do you think the extra height given by removing the case might help?
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DonShole
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« Reply #27 on: February 04, 2007, 03:46:56 PM »

Hi Rumi, have you tried adjusting the pens click sensitivity from lighter to heavier? this may reduce/stop the random clicks.
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Rumi
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« Reply #28 on: February 04, 2007, 09:32:54 PM »

Drew: I might have to try that, but I am not looking forward to unwrapping everything. Maybe what I will do is remove the backlight slab instead and test that way. Although the problem that I am having is that when the pen is lifted to a height where it is almost losing it, it gets confused and thinks the pen has been clicked and it paints these bird droppings on my screen (and I thought bird droppings were meant to bring you luck!) So I would think that decreasing the case height would only mean that the bird droppings will occur at a different pen height. But at this stage I am willing to try anything.

So Drew, do you get more interference when you work on a black photoshop image? What about random clicking?

Don: Yes I tried that but the drivers are a bit funny and after doing adjustments  sometimes I lose pressure sensitivity and I need to reboot so I havent done that many tests. I will try that today see how it goes. I am doing these tests on a PC running Win XP, I couldn't make the tablet work on the Mac (driver problems), but I did get it to work on Linux using the TabletWizard open source drivers (yay for open source!).

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Rumi
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« Reply #29 on: February 05, 2007, 10:22:22 AM »

Ok I tried decreasing the distance between the LCD and the tablet to see if it improved my random clicking problem byt removing the backlight slab. It actually made the random clicking worse. Please note that this is only for my tablet, other tablets like Wacoms use different technology so decreasing the distance may actually help.

I also tried what Don suggested, increasing the hardness of the pen doesn't decrease the random clicks but it does make them less noticeable because they are more faint.
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