DSP/Source/FilteringFunctions/arm_fir_interpolate_init_q15.c

/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_fir_interpolate_init_q15.c
 * Description:  Q15 FIR interpolator initialization function
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 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"

/**
  @ingroup groupFilters
 */

/**
  @addtogroup FIR_Interpolate
  @{
 */

/**
  @brief         Initialization function for the Q15 FIR interpolator.
  @param[in,out] S         points to an instance of the Q15 FIR interpolator structure
  @param[in]     L         upsample factor
  @param[in]     numTaps   number of filter coefficients in the filter
  @param[in]     pCoeffs   points to the filter coefficient buffer
  @param[in]     pState    points to the state buffer
  @param[in]     blockSize number of input samples to process per call
  @return        execution status
                   - \ref ARM_MATH_SUCCESS        : Operation successful
                   - \ref ARM_MATH_ARGUMENT_ERROR : filter length <code>numTaps</code> is not a multiple of the interpolation factor <code>L</code>


  @par           Details
                   <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:
  <pre>
      {b[numTaps-1], b[numTaps-2], b[numTaps-2], ..., b[1], b[0]}
  </pre>
                   The length of the filter <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code>.
  @par
                   <code>pState</code> points to the array of state variables.
                   <code>pState</code> is of length <code>(numTaps/L)+blockSize-1</code> words
                   where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_interpolate_q15()</code>.
 */

arm_status arm_fir_interpolate_init_q15(
        arm_fir_interpolate_instance_q15 * S,
        uint8_t L,
        uint16_t numTaps,
  const q15_t * pCoeffs,
        q15_t * pState,
        uint32_t blockSize)
{
  arm_status status;

  /* The filter length must be a multiple of the interpolation factor */
  if ((numTaps % L) != 0U)
  {
    /* Set status as ARM_MATH_LENGTH_ERROR */
    status = ARM_MATH_LENGTH_ERROR;
  }
  else
  {
    /* Assign coefficient pointer */
    S->pCoeffs = pCoeffs;

    /* Assign Interpolation factor */
    S->L = L;

    /* Assign polyPhaseLength */
    S->phaseLength = numTaps / L;

    /* Clear state buffer and size of buffer is always phaseLength + blockSize - 1 */
    memset(pState, 0, (blockSize + ((uint32_t) S->phaseLength - 1U)) * sizeof(q15_t));

    /* Assign state pointer */
    S->pState = pState;

    status = ARM_MATH_SUCCESS;
  }

  return (status);
}

/**
  @} end of FIR_Interpolate group
 */