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Problem using real time mode

Gaston_Melo_Arg
Mastermind 7675 points

Hi,

I generate a simple sine wave, but when i want to see it in the graph window  using real time mode i see a random signal, but when i use a toggle breakpoint i get the sine wave in the graph window.  I'm using a f28027 

1) Whats the problem?

Thanks

Gastón

  • 0
    Genius 5885 points

    Hi Gaston!

    In real time mode CCS refreshes the graph window once every 100ms or so. If you have a sine signal with period less then cca 10*100ms then you are undersampling the signal. As Nyquist said it is not possible to reconstruct the original signal if the sampling frequency is less than 2*signal frequency (in practive 10*signal frequency). You can easily check this if you lower your signal frequency

    What you could do is buffer one (or more) period of sine signal somewhere in RAM and than put the entire contents of buffer in graph window. The TI DLOG module form digital motor control library is one possible solution

    Hope this helps

    Regards, Mitja