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some question about the function"gen_twiddle_fft16x16" in DSPLIB of C64pius?

OuyangZhao ouyang
Intellectual 620 points

Hi,

       I use c64 + dsplib library " DSP_fft16x16" functions to achieve N = 256 point fft, but I found the  function "gen_twiddle_fft16x16" that used to  generated twiddle factors only produce 504 data, while the twiddle factors is defined by 2 * N = 512 data,  why? does it will effect the functoin of "DSP_fft16x16",because the  twiddle factors is used in the function.

Thanks,

Ouyang

  

  • 0
    TI__Guru** 116170 points

    What version of the DSPLIB are you refering to. Looking at the gan_twiddle_fft16x16 function in DSPLIB 3.x, it appears that it would generate 512 data and not 504 as you have indicated. Please ensure you are using the DSPLIB 3.x and let us know if this is still an issue.

    Regards,

    Rahul

  • 0 in reply to Rahul Prabhu
    Intellectual 620 points

    Hi,

             yes, i am using DSPLIB3.X,in the function gen_twiddle_fft16x16 function to do N=256 points fft,in the gen_twiddle_fft16x16 function each inner loop generates  12 twiddle factors,according to the restrictions i and j ,the function only within the inner loop 42 cycles, only 504 points generated.  first twiddle factors is initialized to 0, after calling function found only in front of 504 data changes.

             Thanks very much.

    Regards,

    Ouyang