DSP/Source/TransformFunctions/arm_cfft_q15.c

/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_cfft_q15.c
 * Description:  Combined Radix Decimation in Q15 Frequency CFFT processing function
 *
 * $Date:        27. January 2017
 * $Revision:    V.1.5.1
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

extern void arm_radix4_butterfly_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    q15_t * pCoef,
    uint32_t twidCoefModifier);

extern void arm_radix4_butterfly_inverse_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    q15_t * pCoef,
    uint32_t twidCoefModifier);

extern void arm_bitreversal_16(
    uint16_t * pSrc,
    const uint16_t bitRevLen,
    const uint16_t * pBitRevTable);

void arm_cfft_radix4by2_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    const q15_t * pCoef);

void arm_cfft_radix4by2_inverse_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    const q15_t * pCoef);

/**
* @ingroup groupTransforms
*/

/**
* @addtogroup ComplexFFT
* @{
*/

/**
* @details
* @brief       Processing function for the Q15 complex FFT.
* @param[in]      *S    points to an instance of the Q15 CFFT structure.
* @param[in, out] *p1   points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place.
* @param[in]     ifftFlag       flag that selects forward (ifftFlag=0) or inverse (ifftFlag=1) transform.
* @param[in]     bitReverseFlag flag that enables (bitReverseFlag=1) or disables (bitReverseFlag=0) bit reversal of output.
* @return none.
*/

void arm_cfft_q15(
    const arm_cfft_instance_q15 * S,
    q15_t * p1,
    uint8_t ifftFlag,
    uint8_t bitReverseFlag)
{
    uint32_t L = S->fftLen;

    if (ifftFlag == 1U)
    {
        switch (L)
        {
        case 16:
        case 64:
        case 256:
        case 1024:
        case 4096:
            arm_radix4_butterfly_inverse_q15  ( p1, L, (q15_t*)S->pTwiddle, 1 );
            break;

        case 32:
        case 128:
        case 512:
        case 2048:
            arm_cfft_radix4by2_inverse_q15  ( p1, L, S->pTwiddle );
            break;
        }
    }
    else
    {
        switch (L)
        {
        case 16:
        case 64:
        case 256:
        case 1024:
        case 4096:
            arm_radix4_butterfly_q15  ( p1, L, (q15_t*)S->pTwiddle, 1 );
            break;

        case 32:
        case 128:
        case 512:
        case 2048:
            arm_cfft_radix4by2_q15  ( p1, L, S->pTwiddle );
            break;
        }
    }

    if ( bitReverseFlag )
        arm_bitreversal_16((uint16_t*)p1,S->bitRevLength,S->pBitRevTable);
}

/**
* @} end of ComplexFFT group
*/

void arm_cfft_radix4by2_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    const q15_t * pCoef)
{
    uint32_t i;
    uint32_t n2;
    q15_t p0, p1, p2, p3;
#if defined (ARM_MATH_DSP)
    q31_t T, S, R;
    q31_t coeff, out1, out2;
    const q15_t *pC = pCoef;
    q15_t *pSi = pSrc;
    q15_t *pSl = pSrc + fftLen;
#else
    uint32_t ia, l;
    q15_t xt, yt, cosVal, sinVal;
#endif

    n2 = fftLen >> 1;

#if defined (ARM_MATH_DSP)

    for (i = n2; i > 0; i--)
    {
        coeff = _SIMD32_OFFSET(pC);
        pC += 2;

        T = _SIMD32_OFFSET(pSi);
        T = __SHADD16(T, 0); // this is just a SIMD arithmetic shift right by 1

        S = _SIMD32_OFFSET(pSl);
        S = __SHADD16(S, 0); // this is just a SIMD arithmetic shift right by 1

        R = __QSUB16(T, S);

        _SIMD32_OFFSET(pSi) = __SHADD16(T, S);
        pSi += 2;

    #ifndef ARM_MATH_BIG_ENDIAN

        out1 = __SMUAD(coeff, R) >> 16;
        out2 = __SMUSDX(coeff, R);

    #else

        out1 = __SMUSDX(R, coeff) >> 16U;
        out2 = __SMUAD(coeff, R);

    #endif //     #ifndef ARM_MATH_BIG_ENDIAN

        _SIMD32_OFFSET(pSl) =
        (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
        pSl += 2;
    }

#else //    #if defined (ARM_MATH_DSP)

    ia = 0;
    for (i = 0; i < n2; i++)
    {
        cosVal = pCoef[ia * 2];
        sinVal = pCoef[(ia * 2) + 1];
        ia++;

        l = i + n2;

        xt = (pSrc[2 * i] >> 1U) - (pSrc[2 * l] >> 1U);
        pSrc[2 * i] = ((pSrc[2 * i] >> 1U) + (pSrc[2 * l] >> 1U)) >> 1U;

        yt = (pSrc[2 * i + 1] >> 1U) - (pSrc[2 * l + 1] >> 1U);
        pSrc[2 * i + 1] =
        ((pSrc[2 * l + 1] >> 1U) + (pSrc[2 * i + 1] >> 1U)) >> 1U;

        pSrc[2U * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) +
                  ((int16_t) (((q31_t) yt * sinVal) >> 16)));

        pSrc[2U * l + 1U] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) -
                       ((int16_t) (((q31_t) xt * sinVal) >> 16)));
    }

#endif //    #if defined (ARM_MATH_DSP)

    // first col
    arm_radix4_butterfly_q15( pSrc, n2, (q15_t*)pCoef, 2U);
    // second col
    arm_radix4_butterfly_q15( pSrc + fftLen, n2, (q15_t*)pCoef, 2U);

    for (i = 0; i < fftLen >> 1; i++)
    {
        p0 = pSrc[4*i+0];
        p1 = pSrc[4*i+1];
        p2 = pSrc[4*i+2];
        p3 = pSrc[4*i+3];

        p0 <<= 1;
        p1 <<= 1;
        p2 <<= 1;
        p3 <<= 1;

        pSrc[4*i+0] = p0;
        pSrc[4*i+1] = p1;
        pSrc[4*i+2] = p2;
        pSrc[4*i+3] = p3;
    }
}

void arm_cfft_radix4by2_inverse_q15(
    q15_t * pSrc,
    uint32_t fftLen,
    const q15_t * pCoef)
{
    uint32_t i;
    uint32_t n2;
    q15_t p0, p1, p2, p3;
#if defined (ARM_MATH_DSP)
    q31_t T, S, R;
    q31_t coeff, out1, out2;
    const q15_t *pC = pCoef;
    q15_t *pSi = pSrc;
    q15_t *pSl = pSrc + fftLen;
#else
    uint32_t ia, l;
    q15_t xt, yt, cosVal, sinVal;
#endif

    n2 = fftLen >> 1;

#if defined (ARM_MATH_DSP)

    for (i = n2; i > 0; i--)
    {
        coeff = _SIMD32_OFFSET(pC);
        pC += 2;

        T = _SIMD32_OFFSET(pSi);
        T = __SHADD16(T, 0); // this is just a SIMD arithmetic shift right by 1

        S = _SIMD32_OFFSET(pSl);
        S = __SHADD16(S, 0); // this is just a SIMD arithmetic shift right by 1

        R = __QSUB16(T, S);

        _SIMD32_OFFSET(pSi) = __SHADD16(T, S);
        pSi += 2;

    #ifndef ARM_MATH_BIG_ENDIAN

        out1 = __SMUSD(coeff, R) >> 16;
        out2 = __SMUADX(coeff, R);
    #else

        out1 = __SMUADX(R, coeff) >> 16U;
        out2 = __SMUSD(__QSUB(0, coeff), R);

    #endif //     #ifndef ARM_MATH_BIG_ENDIAN

        _SIMD32_OFFSET(pSl) =
        (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
        pSl += 2;
    }

#else //    #if defined (ARM_MATH_DSP)

    ia = 0;
    for (i = 0; i < n2; i++)
    {
        cosVal = pCoef[ia * 2];
        sinVal = pCoef[(ia * 2) + 1];
        ia++;

        l = i + n2;
        xt = (pSrc[2 * i] >> 1U) - (pSrc[2 * l] >> 1U);
        pSrc[2 * i] = ((pSrc[2 * i] >> 1U) + (pSrc[2 * l] >> 1U)) >> 1U;

        yt = (pSrc[2 * i + 1] >> 1U) - (pSrc[2 * l + 1] >> 1U);
        pSrc[2 * i + 1] =
          ((pSrc[2 * l + 1] >> 1U) + (pSrc[2 * i + 1] >> 1U)) >> 1U;

        pSrc[2U * l] = (((int16_t) (((q31_t) xt * cosVal) >> 16)) -
                        ((int16_t) (((q31_t) yt * sinVal) >> 16)));

        pSrc[2U * l + 1U] = (((int16_t) (((q31_t) yt * cosVal) >> 16)) +
                           ((int16_t) (((q31_t) xt * sinVal) >> 16)));
    }

#endif //    #if defined (ARM_MATH_DSP)

    // first col
    arm_radix4_butterfly_inverse_q15( pSrc, n2, (q15_t*)pCoef, 2U);
    // second col
    arm_radix4_butterfly_inverse_q15( pSrc + fftLen, n2, (q15_t*)pCoef, 2U);

    for (i = 0; i < fftLen >> 1; i++)
    {
        p0 = pSrc[4*i+0];
        p1 = pSrc[4*i+1];
        p2 = pSrc[4*i+2];
        p3 = pSrc[4*i+3];

        p0 <<= 1;
        p1 <<= 1;
        p2 <<= 1;
        p3 <<= 1;

        pSrc[4*i+0] = p0;
        pSrc[4*i+1] = p1;
        pSrc[4*i+2] = p2;
        pSrc[4*i+3] = p3;
    }
}