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Hissing sound during and after playing wave file

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  • #16


    Thank you for the tip, but can't make it work properly either.
    I unsticked the LCD with the touch-screen to see if this noise was induced by the touch-panel itself, but it appears not to come from it directly.
    One issue I see is that on the Picaso chip, the two pins YD and XL for the touch panel are just nearby the audio output pin. And as the refreshment of the touch panel is about 1kHz, it is induced by crosstalk in the audio at his point and all along up to R21. I also noticed that the capacitors C28 and C30 (on XR and YU lines) are not mounted, but this does nothing.
    Is it possible to diminish the refreshment frequency of the touch panel?

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    • #17


      Are you saying the noise is there only when touch is turned on?
      Mark

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      • #18


        Yes, when I disable touch, the noise stops.

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        • #19


          Well, that doesn't make much sense.



          What comes from Audio is PWM, the Touch could only introduce AM noise on the audio line.



          The 74LC08 (with clean 'analogue' power) should completely remove any AM noise on the PWM.



          Mark

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