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Thread: Calibrating touch screen display

  1. #1
    Junior Member
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    Jan 2017
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    Calibrating touch screen display

    Hi all,
    I'm using the color touchscreen display and am making good progress. When I look at the raw numbers of touch point coordinates, they clearly have no relationship to the underlying pixel coordinate. I've looked through the threads on this forum, and at least one thread referred to calibrating the touchscreen so the top left and bottom right values are known. I've tried doing this with the tip of a retracted ball point pen and the values seem to vary quite widely even when I'm within a millimeter or so of my last touch. Is there any trick, or are there set numbers?

    Thanks.

    Ed

  2. #2
    Senior Member+ defragster's Avatar
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    It has been a while but I did this 'back then'

    See if this thread/post or following post makes any sense and has a tested solution: https://forum.pjrc.com/threads/39878...l=1#post124208

  3. #3
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    Thank you. I thought perhaps there were known parameters, but I guess each one of the little guys is different.

  4. #4
    Senior Member+ defragster's Avatar
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    What I came up with in that code worked for the ones I had from eBay and PJRC - and for others with the same display AFAIK. There was some rumble about not working - but never got feedback from those users to adjust or understand if something changed.

    To get those numbers I just ran the touch sample showing values on the screen - then touched the screen and ran off all four edges to see the last number reported in some fashion. Those MAX/MIN values for X and Y go into the MAP array and as I set it up ( hopefully in linked code ) the map function gets display pixel right (+/-) in any rotated orientation.

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