FFT calculation problem using TMS320C6416

Hello to all ,
I am pretty new to this subject so please bare with me ..I am just
trying to do a basic FFT calculation code using the Code Composer Studio
(CCS v5)  my goal is to see the number of clock cycles to compute a
Radix-2 FFT;  the input is a 256 points sine wave,  now if i try to see
the FFT magnitude which is supposed to be a dirac impulse, the plot
comes out to be random..i'll put my code in here, maybe i'm missing
something; Can anyone help me Please..!


#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <dsp_radix2.h>
#include <dsp_fltoq15.h>

#define PI (3.141592654)
#define N (256)

float x[N];
short  y[N];



int gen_twiddle(short *w, int n, double scale)
{
    double angle, step;
    int i;

    step = (2.0 * PI) / (double)n;

    for (i = 0, angle = 0.0; i < n; i += 2, angle += step)
    {
        w[i + 0] = d2s(scale * -cos(angle));
        w[i + 1] = d2s(scale * -sin(angle));
    }

    return n;
}

int main(void)
{
	int i, size;
	double scale = 32767.5;
	short *w;



	for(i=1; i<N; i++)
	{
		x[i] = sin(2 * PI *10 * i/N);

	}

	DSP_fltoq15(x,y,N); //float to Q15 format.

	/*========================================================= */
		    			/*Generate the twiddle-factor array*/
    /*=========================================================== */

		    size = gen_twiddle(w, N, scale);

		    printf("const short w[2 * %d] =n{", size / 2);
		    for (i = 0; i < size; i++)
		    {
		     	printf("%s%c0x%.4X",
		       	i == 0 ? "n    " : (i & 7) == 0 ? ",n    " : ", ",
	            w[i] < 0 ? '-' : ' ', abs(w[i]));

	        }
		    printf("n};n");

	/*========================================================= */
  /*Perform the Radix 2 FFT routine using the function predifined in the
DSP library*/
    /*=========================================================== */

		    DSP_radix2(N, y, w);

}



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