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issue with value steps up and down without a reason -28035

Chris15800
Prodigy 140 points

Hi,

I count a float / int variable up to 100 and logg the data, is the value 100 i set it back to 0.

in the sawtoth i have steps and the ramp works after the step normaly but i don´t can find a reason for the steps.


I write the value to the epwm show the value withe the oszi and the steps are not a displayproblem withe the time/frequency graph it is a real step in the value...

The steps are in the variables in my epwm and in independent variables in the idle loop mostly at the same time.

Thanks for help.

 

Chris

 


  • 0
    Mastermind 7585 points

    Chris,

    can you explain your problem a little bit more in detail please? You mentioned that you use an ePWM channel. What do you modify by your variable, is it the period or one compare register? What opmode is your PWM running in? With an oscilloscope you cannot display a PWM-pattern as a ramp. You will need an  integrator (low pass filter) at the output line to transform the duty cycles into a relative voltage between 0 and 3.3Volt.  

     

  • 0 in reply to Frank Bormann
    Prodigy 140 points

    Hi,

    i generate a sinwave with the epwm and a low pass filter, the phase angel is a ramp and use the ccs3.3.

    I generate a ramp with a for loop (int i=0,i<250,i++) (if =i=249) i=0; log[i] for examble

    one ramp in the epwm isr and for compare a independent ramp i the idle loop

    I traced different ramps and loged the data for a few periods and the error was presentet in the independent ramp more than in the isr ramp.

    In the independent ramp the value goes up and after a short time (the time is different) the value goes down with the same value.

    In the isr ramp the value steps and do not step back.

    Withe the oszi it can be a triger problem. Is it possible that the error is a triger problem in the graph funktion.

     

    Thanks for help