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promble of FFT for F28377D use!!help!!

guodong cao
Prodigy 90 points


HI everybody!

i am using F28377D for a THD calculate , but now i got TWO prombles for help!

in order to finish this calculate , FFT procedure is necessary, so i use the program in controlsuit  named "2837x_vcu2_rfft_256",but i don not know clearly that what dose the oupput array sequence means.

fot example:if the output array is 1,2,3,4,5,6,7,8,9;do all these numbers are for X(k),(k=0.1.2.3......)

                    OR    1 for the  real part of X(0),2 for the imaginary part of X(0)......

AND THE second question is  i want to transplant this program to another ,but i can not find the content of 

subfunction which named "CFFT_init128Pt" and it is located in "vcu2_fft.h",when i transplant this program to another,build error shows that  "CFFT_init128Pt" is undefined.........for help!!!!!!

how can i use this for THD calculate,THANKS FOR ALL!!

  • 0
    Intellectual 540 points

    Hi Cao,


    I am a new user of the TI's device.Hope I can do help for you -- In most case I can not :)

    About the second question -- the "CFFT_init128Pt" is undefined -- you need not only the header file, but also the C source code which defined the function, or if this function were defined in a lib, and you included this lib file.

    I don't know the details, but if you can find a file 'vcu2_fft.c', that will be the file with source code. Otherwise, you need to read the manual and find out the solution.

    Bests,

    King

  • 0
    TI__Mastermind 20850 points

    Hi,

    since you are using the VCU library, you can check chapter 3 of the user's guide for information on how to inlcude the library in your porject. The error "CFFT_init128Pt is undefined" is due to the fact that your project cannot find the C28x_vcu_library.lib file. 

    If you refer to chapter 3 there is a step by step description of how to integrate the library. 

  • 0
    Intellectual 540 points

    Hi Cao,

    Also take care about the data structure, the FFT function may use a structure instead of real/image data in turn.

    Today I studied this part for my program, and I used a function like "CFFT_f32(&cfft);", here the cfft is a structure, stores the input data (real/image/real/image in turn), the magnitude of FFT, the output data, the sine-coef and so on.

    So, read the manual at first.

    Bests,

    King