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Original question:

TSC2046: Problems with conversion and X/Y measurement

TSC2046: Calibration's algorithm values

luigi Quaglia
Expert 1155 points

Part Number: TSC2046

Good Morning everybody!

I'm creating my touch screen calibration function according to the article Calibration in touch-screen systems by W.Fang and T.Chang.

I drew three different indipendent points and then I read the values of X and Y for each point.

Everything works fine until here!
The problems start when I calculate:

det A

det AX1          det AY1

det AX2          det AY2

det Ax3          det AY3

Is it possible that some of these values are NEGATIVE?

Why does this happen?

Any advice and help to understand what's wrong (if there is something wrong) would be really appreciated.

Best regards,

Luigi

  • 0
    TI__Mastermind 22950 points

    Hello Luigi,

    Great question! It is possible for values to be negative. The determinant of a matrix can be denoted by "bars'' on the sides of the matrix. This does not represent the absolute value. The sign of a determinant indicates whether the orientation of the transform has been preserved or flipped. 

    On the top of page 8 in the article, you can even see that some negative values were calculated for the Y coordinate equation. Hope this helps!

    Regards,

    Aaron