arm_fir_interpolate_init_q15.c

00001 /* ----------------------------------------------------------------------
00002  * Project:      CMSIS DSP Library
00003  * Title:        arm_fir_interpolate_init_q15.c
00004  * Description:  Q15 FIR interpolator initialization function
00005  *
00006  * $Date:        27. January 2017
00007  * $Revision:    V.1.5.1
00008  *
00009  * Target Processor: Cortex-M cores
00010  * -------------------------------------------------------------------- */
00011 /*
00012  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
00013  *
00014  * SPDX-License-Identifier: Apache-2.0
00015  *
00016  * Licensed under the Apache License, Version 2.0 (the License); you may
00017  * not use this file except in compliance with the License.
00018  * You may obtain a copy of the License at
00019  *
00020  * www.apache.org/licenses/LICENSE-2.0
00021  *
00022  * Unless required by applicable law or agreed to in writing, software
00023  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00024  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00025  * See the License for the specific language governing permissions and
00026  * limitations under the License.
00027  */
00028 
00029 #include "arm_math.h"
00030 
00031 /**
00032  * @ingroup groupFilters
00033  */
00034 
00035 /**
00036  * @addtogroup FIR_Interpolate
00037  * @{
00038  */
00039 
00040 /**
00041  * @brief  Initialization function for the Q15 FIR interpolator.
00042  * @param[in,out] *S        points to an instance of the Q15 FIR interpolator structure.
00043  * @param[in]     L         upsample factor.
00044  * @param[in]     numTaps   number of filter coefficients in the filter.
00045  * @param[in]     *pCoeffs  points to the filter coefficient buffer.
00046  * @param[in]     *pState   points to the state buffer.
00047  * @param[in]     blockSize number of input samples to process per call.
00048  * @return        The function returns ARM_MATH_SUCCESS if initialization was successful or ARM_MATH_LENGTH_ERROR if
00049  * the filter length <code>numTaps</code> is not a multiple of the interpolation factor <code>L</code>.
00050  *
00051  * <b>Description:</b>
00052  * \par
00053  * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:
00054  * <pre>
00055  *    {b[numTaps-1], b[numTaps-2], b[numTaps-2], ..., b[1], b[0]}
00056  * </pre>
00057  * The length of the filter <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code>.
00058  * \par
00059  * <code>pState</code> points to the array of state variables.
00060  * <code>pState</code> is of length <code>(numTaps/L)+blockSize-1</code> words
00061  * where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_interpolate_q15()</code>.
00062  */
00063 
00064 arm_status arm_fir_interpolate_init_q15(
00065   arm_fir_interpolate_instance_q15 * S,
00066   uint8_t L,
00067   uint16_t numTaps,
00068   q15_t * pCoeffs,
00069   q15_t * pState,
00070   uint32_t blockSize)
00071 {
00072   arm_status status;
00073 
00074   /* The filter length must be a multiple of the interpolation factor */
00075   if ((numTaps % L) != 0U)
00076   {
00077     /* Set status as ARM_MATH_LENGTH_ERROR */
00078     status = ARM_MATH_LENGTH_ERROR;
00079   }
00080   else
00081   {
00082 
00083     /* Assign coefficient pointer */
00084     S->pCoeffs = pCoeffs;
00085 
00086     /* Assign Interpolation factor */
00087     S->L = L;
00088 
00089     /* Assign polyPhaseLength */
00090     S->phaseLength = numTaps / L;
00091 
00092     /* Clear state buffer and size of buffer is always phaseLength + blockSize - 1 */
00093     memset(pState, 0,
00094            (blockSize + ((uint32_t) S->phaseLength - 1U)) * sizeof(q15_t));
00095 
00096     /* Assign state pointer */
00097     S->pState = pState;
00098 
00099     status = ARM_MATH_SUCCESS;
00100   }
00101 
00102   return (status);
00103 
00104 }
00105 
00106  /**
00107   * @} end of FIR_Interpolate group
00108   */
00109