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    • PWM noise on gpio - F2803x

    PWM noise on gpio - F2803x

    This question is not answered
    Amr Amin
    Posted by
    on Aug 02 2012 11:27 AM
    Prodigy20 points

    I'm using the HRPWM example code (F2803x - v126) on my F28035 development board. There is a pwm noise signal on some of the unused gpio pins. How do I get rid of this noise?

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    • Kris Parrent
      Posted by
      on Aug 02 2012 16:57 PM
      Expert6005 points

      First things I would suggest:

      If the pin is an input, enable the pull up resistor.  If this doesn't work, set it as an output and drive it high or low.  There's also a possibility it is just your scope lead picking up the noise from the neighboring pin and it is not actually present on the pin itself.

      I can't imagine there is a significant amount of noise on the pin.  What is the concern if the IO is not being used?

      Kris

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    • Amr Amin
      Posted by
      on Aug 03 2012 12:15 PM
      Prodigy20 points

      Hi,

      Thank you for your response.

      I implemented your suggestions, but unfortunately the problem remains.

      For simplicity, I only configured hrpwm1 (i.e. gpio0 and gpio1).

      1. I made the other gpio pins gpio-inputs and tried both enabling and disabling the pull-up resistor. Outcome: a square wave pwm noise (350mV pk-pk) appeared on gpio2. A similar pwm noise appeared on the other gpio pins, but the pk-pk value decreased as I measured further gpio pins. 
      2. I set the other gpio pins as outputs and forced them low.  Outcome: The pwm noise was no longer present, but there were voltage spikes at the same points in time that hrpwm1 toggled.
      3. I tried both a different scope and measuring the pins directly. Outcome: no difference.
      4. Finally, I tried a different development board. Outcome: no difference. 
      I'm using the Piccolo F28035 development board. 
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