Wrong touch coordinates detection

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    • Wrong touch coordinates detection


      I'm developing a user interface on a 320x240 display, with 4-wire analog touch interface. Everything is working well, just touch seems to be to much rough.
      Our problem is that, even if we calibrate the touchscreen with a 9 points method, still persist a lot of wrong revealed touch: i.e., with reference to the image attacched, finger is pressed on the button '+' (45x45 pixels), but the library detect a touch on the slider, at least 20 pixels over the button itself.

      Calibration is done run-time: once the user has touched all the required points, whose x and y values are retrieved through GUI_TOUCH_GetState() and used to build-up a 2-dimensional array. At the end, logical points and their corresponding ADC values are passed to GUI_TOUCH_CalcCoefficients() to let emWin evaluate calibration coefficients; finally, calibration is automatically enabled with GUI_TOUCH_EnableCalibration(1) so that analog data passed to GUI_PID_StoreState() are already calibrated.
      This is how we implemented calibration.

      Using a smaller object, such as a pen, to touch the screen instead of the finger, we can achieve a little better result, but wrong points detection keep to exist.
      Any suggestion on how to solve this?

      Many thanks
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