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MSP430FR2111: PWM wave is abnormal at the moment of comparator interrupt

Part Number: MSP430FR2111

Hi 

1. Disable comparator interrupt, PWM wave is fine.

2. Once enable  comparator interrupt, as above picture, PWM is pulled down from 3.3V to 2.6V at the moment when rising and falling edge trigger comparator to interrupt.

Add key code as attached. How to resolve the abnormal voltage level? Thanks a lot.

6763.code.docx

  • Hi Daniel,
    according to the code you posted the PWM output should be at P1.7, and according to the datasheet COUT is at P2.0, which are neighbored pins. Could you please double check on one hand, whether there is not a cross link in some way? Also why does channel 4 show 5V and channel 2 1V/div range selection? It looks like a diode link between the two.

    Best regards
    Peter
  • Hi Peter,

    Yes, channel 4 is 5V and channel 2 is 1V/div. Channel 2 is 24V bus which used for bus communication.

    After change it to P1.6, problem is same as before. We also test it on FR2311 launchpad, it's same problem.
  • Hi Daniel,
    so channel 4 is not showing a signal directly from the MSP430. Could you please take a scope shot where the PWM of the MSP430 and the supply voltage of the MSP430 is visible? It might be, that for some reason the supply voltage of the MSP430 is dropping for whatever reasons. That would explain the observed behavior.

    Best regards
    Peter
  • Hi Peter,

    It's resolved now, after we add SYSCFG2 |= TB0TRGSEL; to configure TB0 to be EXTERNAL SOURCE.

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