k60-keil

K60-Keil版本（下载安装MDK4.23）

        s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];

        /* ya - yc */
        s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];

        /* xb + xd */
        t1 = pSrc[2u * i1] + pSrc[2u * i3];

        /* xa' = xa + xb + xc + xd */
        pSrc[2u * i0] = r1 + t1;

        /* xa + xc -(xb + xd) */
        r1 = r1 - t1;

        /* yb + yd */
        t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];

        /* ya' = ya + yb + yc + yd */
        pSrc[(2u * i0) + 1u] = s1 + t2;

        /* (ya + yc) - (yb + yd) */
        s1 = s1 - t2;

        /* (yb - yd) */
        t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];

        /* (xb - xd) */
        t2 = pSrc[2u * i1] - pSrc[2u * i3];

        /* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
        pSrc[2u * i1] = (r1 * co2) - (s1 * si2);

        /* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
        pSrc[(2u * i1) + 1u] = (s1 * co2) + (r1 * si2);

        /* (xa - xc) - (yb - yd) */
        r1 = r2 - t1;

        /* (xa - xc) + (yb - yd) */
        r2 = r2 + t1;

        /* (ya - yc) +  (xb - xd) */
        s1 = s2 + t2;

        /* (ya - yc) -  (xb - xd) */
        s2 = s2 - t2;

        /* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
        pSrc[2u * i2] = (r1 * co1) - (s1 * si1);

        /* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
        pSrc[(2u * i2) + 1u] = (s1 * co1) + (r1 * si1);

        /* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
        pSrc[2u * i3] = (r2 * co3) - (s2 * si3);

        /* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
        pSrc[(2u * i3) + 1u] = (s2 * co3) + (r2 * si3);
      }
    }
    twidCoefModifier <<= 2u;
  }

  /*  Initializations of last stage */
  n1 = n2;
  n2 >>= 2u;

  /*  Calculations of last stage */
  for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1)
  {
    /*  index calculation for the input as, */
    /*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
    i1 = i0 + n2;
    i2 = i1 + n2;
    i3 = i2 + n2;

    /*  Butterfly implementation */
    /* xa + xc */
    r1 = pSrc[2u * i0] + pSrc[2u * i2];

    /* xa - xc */
    r2 = pSrc[2u * i0] - pSrc[2u * i2];

    /* ya + yc */
    s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];

    /* ya - yc */
    s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];

    /* xc + xd */
    t1 = pSrc[2u * i1] + pSrc[2u * i3];

    /* xa' = xa + xb + xc + xd */
    pSrc[2u * i0] = (r1 + t1) * onebyfftLen;

    /* (xa + xb) - (xc + xd) */
    r1 = r1 - t1;

    /* yb + yd */
    t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];

    /* ya' = ya + yb + yc + yd */
    pSrc[(2u * i0) + 1u] = (s1 + t2) * onebyfftLen;

    /* (ya + yc) - (yb + yd) */
    s1 = s1 - t2;

    /* (yb-yd) */
    t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];

    /* (xb-xd) */
    t2 = pSrc[2u * i1] - pSrc[2u * i3];

    /* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
    pSrc[2u * i1] = r1 * onebyfftLen;

    /* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
    pSrc[(2u * i1) + 1u] = s1 * onebyfftLen;


    /* (xa - xc) - (yb-yd) */
    r1 = r2 - t1;

    /* (xa - xc) + (yb-yd) */
    r2 = r2 + t1;

    /* (ya - yc) + (xb-xd) */
    s1 = s2 + t2;

    /* (ya - yc) - (xb-xd) */
    s2 = s2 - t2;

    /* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
    pSrc[2u * i2] = r1 * onebyfftLen;

    /* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
    pSrc[(2u * i2) + 1u] = s1 * onebyfftLen;

    /* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
    pSrc[2u * i3] = r2 * onebyfftLen;

    /* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
    pSrc[(2u * i3) + 1u] = s2 * onebyfftLen;
  }


#else

  /* Run the below code for Cortex-M0 */

  /*  Initializations for the first stage */
  n2 = fftLen;
  n1 = n2;

  /*  Calculation of first stage */
  for (k = fftLen; k > 4u; k >>= 2u)
  {
    /*  Initializations for the first stage */
    n1 = n2;
    n2 >>= 2u;
    ia1 = 0u;

    /*  Calculation of first stage */
    for (j = 0u; j <= (n2 - 1u); j++)
    {
      /*  index calculation for the coefficients */
      ia2 = ia1 + ia1;
      ia3 = ia2 + ia1;
      co1 = pCoef[ia1 * 2u];
      si1 = pCoef[(ia1 * 2u) + 1u];
      co2 = pCoef[ia2 * 2u];
      si2 = pCoef[(ia2 * 2u) + 1u];
      co3 = pCoef[ia3 * 2u];
      si3 = pCoef[(ia3 * 2u) + 1u];

      /*  Twiddle coefficients index modifier */
      ia1 = ia1 + twidCoefModifier;

      for (i0 = j; i0 < fftLen; i0 += n1)
      {
        /*  index calculation for the input as, */
        /*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
        i1 = i0 + n2;
        i2 = i1 + n2;
        i3 = i2 + n2;

        /* xa + xc */
        r1 = pSrc[(2u * i0)] + pSrc[(2u * i2)];

        /* xa - xc */
        r2 = pSrc[(2u * i0)] - pSrc[(2u * i2)];

        /* ya + yc */
        s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];

        /* ya - yc */
        s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];

        /* xb + xd */
        t1 = pSrc[2u * i1] + pSrc[2u * i3];

        /* xa' = xa + xb + xc + xd */
        pSrc[2u * i0] = r1 + t1;

        /* xa + xc -(xb + xd) */
        r1 = r1 - t1;

        /* yb + yd */
        t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];

        /* ya' = ya + yb + yc + yd */
        pSrc[(2u * i0) + 1u] = s1 + t2;

        /* (ya + yc) - (yb + yd) */
        s1 = s1 - t2;

        /* (yb - yd) */
        t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];

        /* (xb - xd) */
        t2 = pSrc[2u * i1] - pSrc[2u * i3];

        /* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
        pSrc[2u * i1] = (r1 * co2) - (s1 * si2);

        /* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
        pSrc[(2u * i1) + 1u] = (s1 * co2) + (r1 * si2);

        /* (xa - xc) - (yb - yd) */
        r1 = r2 - t1;

        /* (xa - xc) + (yb - yd) */
        r2 = r2 + t1;

        /* (ya - yc) +  (xb - xd) */
        s1 = s2 + t2;

        /* (ya - yc) -  (xb - xd) */
        s2 = s2 - t2;

        /* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
        pSrc[2u * i2] = (r1 * co1) - (s1 * si1);

        /* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
        pSrc[(2u * i2) + 1u] = (s1 * co1) + (r1 * si1);

        /* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
        pSrc[2u * i3] = (r2 * co3) - (s2 * si3);

        /* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
        pSrc[(2u * i3) + 1u] = (s2 * co3) + (r2 * si3);
      }
    }
    twidCoefModifier <<= 2u;
  }
  /*  Initializations of last stage */
  n1 = n2;
  n2 >>= 2u;

  /*  Calculations of last stage */
  for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1)
  {
    /*  index calculation for the input as, */
    /*  pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
    i1 = i0 + n2;
    i2 = i1 + n2;
    i3 = i2 + n2;

    /*  Butterfly implementation */
    /* xa + xc */
    r1 = pSrc[2u * i0] + pSrc[2u * i2];

    /* xa - xc */
    r2 = pSrc[2u * i0] - pSrc[2u * i2];

    /* ya + yc */
    s1 = pSrc[(2u * i0) + 1u] + pSrc[(2u * i2) + 1u];

    /* ya - yc */
    s2 = pSrc[(2u * i0) + 1u] - pSrc[(2u * i2) + 1u];

    /* xc + xd */
    t1 = pSrc[2u * i1] + pSrc[2u * i3];

    /* xa' = xa + xb + xc + xd */
    pSrc[2u * i0] = (r1 + t1) * onebyfftLen;

    /* (xa + xb) - (xc + xd) */
    r1 = r1 - t1;

    /* yb + yd */
    t2 = pSrc[(2u * i1) + 1u] + pSrc[(2u * i3) + 1u];

    /* ya' = ya + yb + yc + yd */
    pSrc[(2u * i0) + 1u] = (s1 + t2) * onebyfftLen;

    /* (ya + yc) - (yb + yd) */
    s1 = s1 - t2;

    /* (yb-yd) */
    t1 = pSrc[(2u * i1) + 1u] - pSrc[(2u * i3) + 1u];

    /* (xb-xd) */
    t2 = pSrc[2u * i1] - pSrc[2u * i3];

    /* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
    pSrc[2u * i1] = r1 * onebyfftLen;

    /* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
    pSrc[(2u * i1) + 1u] = s1 * onebyfftLen;


    /* (xa - xc) - (yb-yd) */
    r1 = r2 - t1;

    /* (xa - xc) + (yb-yd) */
    r2 = r2 + t1;

    /* (ya - yc) + (xb-xd) */
    s1 = s2 + t2;

    /* (ya - yc) - (xb-xd) */
    s2 = s2 - t2;

    /* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
    pSrc[2u * i2] = r1 * onebyfftLen;

    /* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
    pSrc[(2u * i2) + 1u] = s1 * onebyfftLen;

    /* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
    pSrc[2u * i3] = r2 * onebyfftLen;

    /* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
    pSrc[(2u * i3) + 1u] = s2 * onebyfftLen;
  }

#endif /* #ifndef ARM_MATH_CM0 */

}

/*   
 * @brief  In-place bit reversal function.  
 * @param[in, out] *pSrc        points to the in-place buffer of floating-point data type.  
 * @param[in]      fftSize      length of the FFT.  
 * @param[in]      bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table.  
 * @param[in]      *pBitRevTab  points to the bit reversal table.  
 * @return none.  
 */

void arm_bitreversal_f32(
  float32_t * pSrc,
  uint16_t fftSize,
  uint16_t bitRevFactor,
  uint16_t * pBitRevTab)
{
  uint16_t fftLenBy2, fftLenBy2p1;
  uint16_t i, j;
  float32_t in;

  /*  Initializations */
  j = 0u;
  fftLenBy2 = fftSize >> 1u;
  fftLenBy2p1 = (fftSize >> 1u) + 1u;

  /* Bit Reversal Implementation */
  for (i = 0u; i <= (fftLenBy2 - 2u); i += 2u)
  {
    if(i < j)
    {
      /*  pSrc[i] <-> pSrc[j]; */
      in = pSrc[2u * i];
      pSrc[2u * i] = pSrc[2u * j];
      pSrc[2u * j] = in;

      /*  pSrc[i+1u] <-> pSrc[j+1u] */
      in = pSrc[(2u * i) + 1u];
      pSrc[(2u * i) + 1u] = pSrc[(2u * j) + 1u];
      pSrc[(2u * j) + 1u] = in;

      /*  pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
      in = pSrc[2u * (i + fftLenBy2p1)];
      pSrc[2u * (i + fftLenBy2p1)] = pSrc[2u * (j + fftLenBy2p1)];
      pSrc[2u * (j + fftLenBy2p1)] = in;

      /*  pSrc[i+fftLenBy2p1+1u] <-> pSrc[j+fftLenBy2p1+1u] */
      in = pSrc[(2u * (i + fftLenBy2p1)) + 1u];
      pSrc[(2u * (i + fftLenBy2p1)) + 1u] =
        pSrc[(2u * (j + fftLenBy2p1)) + 1u];
      pSrc[(2u * (j + fftLenBy2p1)) + 1u] = in;

    }

    /*  pSrc[i+1u] <-> pSrc[j+1u] */
    in = pSrc[2u * (i + 1u)];
    pSrc[2u * (i + 1u)] = pSrc[2u * (j + fftLenBy2)];
    pSrc[2u * (j + fftLenBy2)] = in;

    /*  pSrc[i+2u] <-> pSrc[j+2u] */
    in = pSrc[(2u * (i + 1u)) + 1u];
    pSrc[(2u * (i + 1u)) + 1u] = pSrc[(2u * (j + fftLenBy2)) + 1u];
    pSrc[(2u * (j + fftLenBy2)) + 1u] = in;

    /*  Reading the index for the bit reversal */
    j = *pBitRevTab;

    /*  Updating the bit reversal index depending on the fft length  */
    pBitRevTab += bitRevFactor;
  }
}