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Comparing sinusoidal and triangular signals for PWM generation

nithin kurian
Intellectual 450 points

Hi,

     I am using Tiva C series and Keil IDE and I want to generate a PWM signal by comparing the sine wave and triangular wave. Frankly speaking, I don't have much experience with the math functions especially trigonometric functions in C programming. So, can somebody suggest me the solution for this. By googling I had found documents related to this, but for TMS320 or other DSP processors and here I am looking for Tiva C series based solution.

  • 0
    Guru 20670 points

    Hi nithin,

    What exacly do you want the output to be depending on the two waves?

  • 0 in reply to Luis Afonso
    Intellectual 450 points

    Hi Luis,

                  Yes, the output should depend upon the two waves. Also I want to know the difference in using the IQMath library and normal math library. Here the sine pulse will update at regular time interval and the triangular pulse remains constant.

               

         

  • 0 in reply to nithin kurian
    Guru 27285 points

    nithin kurian said:

    Hi Luis,

                  Yes, the output should depend upon the two waves. Also I want to know the difference in using the IQMath library and normal math library. Here the sine pulse will update at regular time interval and the triangular pulse remains constant.

    ??????????????

    ^???? what are you thinking about ?

     from where are coming these two wave/signal, what is the goal?

     Are you using analog to digital  converter?

     Are you using analog comparator or are you doing  what?

  • 0 in reply to Roberto Romano
    Intellectual 840 points

    Luis

    Please tell how to generate sine wave in tiva c using math library. then i want to vary the duty of pwm on the basis of sine wave magnitude.

  • 0 in reply to Prashant Surana
    Guru 20670 points
    First it was read now it's generate?
    Please provide a better and clear description of what you want to do so that there is not confusion

    Anyway if you have solutions for other MCUs you can just port the functionality. Now if you want sample code to avoid extra work well, can't help you, I don't have any ready on the subject.
  • 0 in reply to Luis Afonso
    Intellectual 840 points
    Luis,
    that question was asked by some other fellow.
  • 0 in reply to Prashant Surana
    Expert 2415 points

    Well why did you reply to this thread then, with a (not totally, but mostly) different question? And Luis's request for a more clear description of what you want to do still applies.

    Besides, your question is rather generic in nature - the target of this forum is not really 'all things microcomputing', but rather the specifics of the TM4C line of products. So please, think about what you want to do, search around the net how things like that are generally done, and when you have a clear understanding of what you need to do (what kind of peripherals you need to achieve the desired input/output functions, etc etc), take a look at the TivaWare manual, examples and the specific datasheet for your TM4C processor. Once you have done that, you should be able to either do what you want, or post a more specific question that will allow the forum members to help you further.

  • 0 in reply to Prashant Surana
    Guru 20670 points
    Well I apologize for the confusion.

    But I support Veikko points.
  • 0 in reply to Luis Afonso
    Intellectual 840 points
    Hii Luis and Veikko
    Sorry for inconvenience. Actually he wanted to give sine input through ADC and I want to generate that sine inside processor. So i added my question here. I am using TM4c123G launchpad.
    I know there are two possible methods. one using look-up table and another using IQmath library. I surfed through net but didnt get any help. If someone knows, kindly help.
  • 0 in reply to Prashant Surana
    Guru 20670 points

    Well how would you like to generate a sine wave? Is it with an external DAC?
    Well, I don't know any papers from TI nor did I find any in a quick search.

    But check this one, it explains how to use a DAC to generate music, I think the "2.1.2 Digital Sine waveform pattern preparation" is what interests you:

    http://www.st.com/.../CD00259245.pdf

    I never used the iqmath library but it should have something to get sine functions so you should be able to do what's described on that guide

  • 0 in reply to Luis Afonso
    Guru 27285 points

     Hi Luis, I am clearing remained link to this forum.. REading again this hard to impossible to understand question I got some very old concept from early PWM theory at time called chopper. It is more than 40Yr old.

     Old PWM regulator where generating PWM from an analog comparator where a voltage was setting the PWM duty cycle and the other input was feed by a triangular wave, the output was a rectangular wave with duty cycle proportional to input voltage.

     I suppose in emerging country where culture has not evolved these old concept are obscuring pure math method so it can match some of errant writing and the lot of similar delirant requests.

    So to generate sine wave with PWM inverter a sine wave from a generator was feed to PWM controller, I feel this can be the source of this worst confusion.

     SO modern table driven sine generation is far from understanding if this old culture is in place. I seen some thing of this on some design and documents are recent to use that.

     Luis I wish all friend here be better.