（LIB）使用 FFT

参考https://blog.csdn.net/m0_51220742/article/details/124869371

#include "fft_test.h"

#include "arm_math.h"
#include "arm_const_structs.h"
#include "stdio.h"


#define Fs 100000
#define FFT_LENGTH 1024

float32_t lBufInArray[FFT_LENGTH*2] = {0};
float32_t lBufOutArray[FFT_LENGTH / 2] = {0};
uint16_t ADC_Value[FFT_LENGTH] = {0};

void InitBufInArray(void)
{
  unsigned short i;
  float fx;
  for(i = 0; i < FFT_LENGTH; i++)
  {
    fx = 1024 * sin(2 * PI * i * 13500.0 / Fs)
         + 512 * sin(2 * PI * i * 8500.0 / Fs)
         + 512 * sin(2 * PI * i * 3500.0 / Fs);

    ADC_Value[i] = fx + 2048;
  }
}

void FFT(void)
{
  InitBufInArray();
  for (int i = 0; i < FFT_LENGTH; i++)
  {
    lBufInArray[i * 2] = ADC_Value[i]; //实部赋值
    lBufInArray[i * 2 + 1] = 0; //虚部赋值
  }
  arm_cfft_f32(&arm_cfft_sR_f32_len1024, lBufInArray, 0, 1);
  arm_cmplx_mag_f32(lBufInArray, lBufOutArray, FFT_LENGTH);

  for (int i = 1; i < FFT_LENGTH/2; i++)
  {
    lBufOutArray[i] /= 512;
  }

  for(int16_t i = 1; i < FFT_LENGTH/2; i++)
  {
    printf("%f\n", lBufOutArray[i]);
  }
}