FFT time

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//******************************************************************************
// transform_ex1_fft_fixed_q15 - Real FFT with fixed scaling.
//
// This example demonstrates how to use the msp_fft_auto_q15 API to transform a
// real input data array to the frequency domain using the fast fourier
// transform (FFT) with fixed scaling.
//
// Jeremy Friesenhahn, Brent Peterson
// Texas Instruments Inc.
// April 2016
//******************************************************************************
#include "msp430.h"

#include <math.h>
#include <stdint.h>
#include <stdbool.h>

#include "DSPLib.h"

/* Global defines */
#define SAMPLES     512
#define FS          4096
#define FREQ1       250
#define FREQ2       1000
#define AMPL1       0.25
#define AMPL2       0.10

/* Input vector A */
DSPLIB_DATA(vectorA,MSP_ALIGN_FFT_Q15(SAMPLES))
_q15 vectorA[SAMPLES];

/* Input vector B */
DSPLIB_DATA(vectorB,MSP_ALIGN_FFT_Q15(SAMPLES))
_q15 vectorB[SAMPLES];

/* Allocate DSPLib parameter structures. */
msp_add_q15_params addParams;
msp_fft_q15_params fftParams;

/* Benchmark cycle counts */
volatile uint32_t cycleCount;

void main(void)
{
    float pi;
    float time;
    uint16_t i;
    msp_status status;
    
    /* Disable WDT. */
    WDTCTL = WDTPW + WDTHOLD;
    
    /* Initialize local variables. */
    pi = acosf(-1);

    /*
     * Generate a floating point sine wave and convert to Q15.
     *     time = 1/(SAMPLES*2) * [0:1:SAMPLES-1];
     *     vectorA = AMPL1*sin(2*pi*FREQ1*time);
     *     vectorB = AMPL2*sin(2*pi*FREQ2*time);
     */
    for (i = 0; i < SAMPLES; i++) {
        time = (float)i/(float)FS;
        vectorA[i] = _Q15(AMPL1*sinf(2*pi*FREQ1*time));
        vectorB[i] = _Q15(AMPL2*sinf(2*pi*FREQ2*time));
    }
    
    /* Call vector add function to sum vectorA and vectorB. */
    addParams.length = SAMPLES;
    status = msp_add_q15(&addParams, vectorA, vectorB, vectorB);
    
    /* Check status flag. */
    if (status != MSP_SUCCESS) {
        /* ERROR! */
        __no_operation();
    }
    
    /* Initialize the fft parameter structure. */
    fftParams.length = SAMPLES;
    fftParams.bitReverse = 1;
    fftParams.twiddleTable = msp_cmplx_twiddle_table_512_q15;
    
    /* Call fixed scaling real fft function. */
    msp_benchmarkStart(TIMER_A0_BASE, 16);
    status = msp_fft_fixed_q15(&fftParams, vectorB);
    cycleCount = msp_benchmarkStop(TIMER_A0_BASE);
    
    /* Check status flag. */
    if (status != MSP_SUCCESS) {
        /* ERROR! */
        while(1);
    }
    
    /* End of program. */
    while (1);
}