/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_fir_init_q15.c
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* Description: Q15 FIR filter initialization function
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*
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* $Date: 27. January 2017
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* $Revision: V.1.5.1
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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* @ingroup groupFilters
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*/
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/**
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* @addtogroup FIR
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* @{
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*/
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/**
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* @param[in,out] *S points to an instance of the Q15 FIR filter structure.
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* @param[in] numTaps Number of filter coefficients in the filter. Must be even and greater than or equal to 4.
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* @param[in] *pCoeffs points to the filter coefficients buffer.
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* @param[in] *pState points to the state buffer.
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* @param[in] blockSize is number of samples processed per call.
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* @return The function returns ARM_MATH_SUCCESS if initialization is successful or ARM_MATH_ARGUMENT_ERROR if
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* <code>numTaps</code> is not greater than or equal to 4 and even.
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*
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* <b>Description:</b>
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* \par
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* <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:
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* <pre>
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* {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
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* </pre>
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* Note that <code>numTaps</code> must be even and greater than or equal to 4.
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* To implement an odd length filter simply increase <code>numTaps</code> by 1 and set the last coefficient to zero.
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* For example, to implement a filter with <code>numTaps=3</code> and coefficients
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* <pre>
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* {0.3, -0.8, 0.3}
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* </pre>
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* set <code>numTaps=4</code> and use the coefficients:
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* <pre>
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* {0.3, -0.8, 0.3, 0}.
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* </pre>
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* Similarly, to implement a two point filter
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* <pre>
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* {0.3, -0.3}
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* </pre>
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* set <code>numTaps=4</code> and use the coefficients:
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* <pre>
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* {0.3, -0.3, 0, 0}.
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* </pre>
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* \par
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* <code>pState</code> points to the array of state variables.
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* <code>pState</code> is of length <code>numTaps+blockSize</code>, when running on Cortex-M4 and Cortex-M3 and is of length <code>numTaps+blockSize-1</code>, when running on Cortex-M0 where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_q15()</code>.
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*/
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arm_status arm_fir_init_q15(
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arm_fir_instance_q15 * S,
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uint16_t numTaps,
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q15_t * pCoeffs,
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q15_t * pState,
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uint32_t blockSize)
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{
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arm_status status;
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#if defined (ARM_MATH_DSP)
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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/* The Number of filter coefficients in the filter must be even and at least 4 */
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if (numTaps & 0x1U)
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{
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status = ARM_MATH_ARGUMENT_ERROR;
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}
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else
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{
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/* Assign filter taps */
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S->numTaps = numTaps;
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/* Assign coefficient pointer */
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S->pCoeffs = pCoeffs;
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/* Clear the state buffer. The size is always (blockSize + numTaps ) */
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memset(pState, 0, (numTaps + (blockSize)) * sizeof(q15_t));
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/* Assign state pointer */
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S->pState = pState;
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status = ARM_MATH_SUCCESS;
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}
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return (status);
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#else
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/* Run the below code for Cortex-M0 */
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/* Assign filter taps */
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S->numTaps = numTaps;
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/* Assign coefficient pointer */
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S->pCoeffs = pCoeffs;
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/* Clear the state buffer. The size is always (blockSize + numTaps - 1) */
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memset(pState, 0, (numTaps + (blockSize - 1U)) * sizeof(q15_t));
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/* Assign state pointer */
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S->pState = pState;
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status = ARM_MATH_SUCCESS;
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return (status);
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#endif /* #if defined (ARM_MATH_DSP) */
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}
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/**
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* @} end of FIR group
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*/
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