DSP/Source/FilteringFunctions/arm_lms_init_q31.c

/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_lms_init_q31.c
 * Description:  Q31 LMS filter 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 LMS
  @{
 */

/**
  @brief         Initialization function for Q31 LMS filter.
  @param[in]     S          points to an instance of the Q31 LMS filter structure
  @param[in]     numTaps    number of filter coefficients
  @param[in]     pCoeffs    points to coefficient buffer
  @param[in]     pState     points to state buffer
  @param[in]     mu         step size that controls filter coefficient updates
  @param[in]     blockSize  number of samples to process
  @param[in]     postShift  bit shift applied to coefficients
  @return        none

  @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[N-2], ..., b[1], b[0]}
  </pre>
                   The initial filter coefficients serve as a starting point for the adaptive filter.
                   <code>pState</code> points to an array of length <code>numTaps+blockSize-1</code> samples,
                   where <code>blockSize</code> is the number of input samples processed by each call to
                   <code>arm_lms_q31()</code>.
 */

void arm_lms_init_q31(
  arm_lms_instance_q31 * S,
  uint16_t numTaps,
  q31_t * pCoeffs,
  q31_t * pState,
  q31_t mu,
  uint32_t blockSize,
  uint32_t postShift)
{
  /* Assign filter taps */
  S->numTaps = numTaps;

  /* Assign coefficient pointer */
  S->pCoeffs = pCoeffs;

  /* Clear state buffer and size is always blockSize + numTaps - 1 */
  memset(pState, 0, (numTaps + (blockSize - 1U)) * sizeof(q31_t));

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

  /* Assign Step size value */
  S->mu = mu;

  /* Assign postShift value to be applied */
  S->postShift = postShift;
}

/**
  @} end of LMS group
 */