/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_fir_sparse_q15.c
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* Description: Q15 sparse FIR filter processing 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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* @addtogroup FIR_Sparse
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* @{
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*/
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/**
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* @brief Processing function for the Q15 sparse FIR filter.
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* @param[in] *S points to an instance of the Q15 sparse FIR structure.
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* @param[in] *pSrc points to the block of input data.
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* @param[out] *pDst points to the block of output data
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* @param[in] *pScratchIn points to a temporary buffer of size blockSize.
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* @param[in] *pScratchOut points to a temporary buffer of size blockSize.
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* @param[in] blockSize number of input samples to process per call.
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* @return none.
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*
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* <b>Scaling and Overflow Behavior:</b>
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* \par
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* The function is implemented using an internal 32-bit accumulator.
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* The 1.15 x 1.15 multiplications yield a 2.30 result and these are added to a 2.30 accumulator.
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* Thus the full precision of the multiplications is maintained but there is only a single guard bit in the accumulator.
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* If the accumulator result overflows it will wrap around rather than saturate.
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* After all multiply-accumulates are performed, the 2.30 accumulator is truncated to 2.15 format and then saturated to 1.15 format.
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* In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits.
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*/
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void arm_fir_sparse_q15(
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arm_fir_sparse_instance_q15 * S,
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q15_t * pSrc,
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q15_t * pDst,
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q15_t * pScratchIn,
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q31_t * pScratchOut,
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uint32_t blockSize)
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{
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q15_t *pState = S->pState; /* State pointer */
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q15_t *pIn = pSrc; /* Working pointer for input */
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q15_t *pOut = pDst; /* Working pointer for output */
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q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q15_t *px; /* Temporary pointers for scratch buffer */
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q15_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */
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q15_t *py = pState; /* Temporary pointers for state buffer */
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int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */
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uint32_t delaySize = S->maxDelay + blockSize; /* state length */
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uint16_t numTaps = S->numTaps; /* Filter order */
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int32_t readIndex; /* Read index of the state buffer */
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uint32_t tapCnt, blkCnt; /* loop counters */
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q15_t coeff = *pCoeffs++; /* Read the first coefficient value */
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q31_t *pScr2 = pScratchOut; /* Working pointer for pScratchOut */
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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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q31_t in1, in2; /* Temporary variables */
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/* BlockSize of Input samples are copied into the state buffer */
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/* StateIndex points to the starting position to write in the state buffer */
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arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);
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/* Loop over the number of taps. */
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tapCnt = numTaps;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q15(py, delaySize, &readIndex, 1,
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pb, pb, blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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/* Loop over the blockSize. Unroll by a factor of 4.
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* Compute 4 multiplications at a time. */
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blkCnt = blockSize >> 2;
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while (blkCnt > 0U)
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{
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/* Perform multiplication and store in the scratch buffer */
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*pScratchOut++ = ((q31_t) * px++ * coeff);
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*pScratchOut++ = ((q31_t) * px++ * coeff);
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*pScratchOut++ = ((q31_t) * px++ * coeff);
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*pScratchOut++ = ((q31_t) * px++ * coeff);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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* compute the remaining samples */
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blkCnt = blockSize % 0x4U;
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while (blkCnt > 0U)
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{
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/* Perform multiplication and store in the scratch buffer */
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*pScratchOut++ = ((q31_t) * px++ * coeff);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Loop over the number of taps. */
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tapCnt = (uint32_t) numTaps - 2U;
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while (tapCnt > 0U)
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{
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q15(py, delaySize, &readIndex, 1,
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pb, pb, blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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/* Loop over the blockSize. Unroll by a factor of 4.
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* Compute 4 MACS at a time. */
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blkCnt = blockSize >> 2;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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*pScratchOut++ += (q31_t) * px++ * coeff;
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*pScratchOut++ += (q31_t) * px++ * coeff;
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*pScratchOut++ += (q31_t) * px++ * coeff;
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*pScratchOut++ += (q31_t) * px++ * coeff;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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* compute the remaining samples */
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blkCnt = blockSize % 0x4U;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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*pScratchOut++ += (q31_t) * px++ * coeff;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Decrement the tap loop counter */
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tapCnt--;
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}
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/* Compute last tap without the final read of pTapDelay */
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q15(py, delaySize, &readIndex, 1,
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pb, pb, blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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/* Loop over the blockSize. Unroll by a factor of 4.
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* Compute 4 MACS at a time. */
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blkCnt = blockSize >> 2;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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*pScratchOut++ += (q31_t) * px++ * coeff;
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*pScratchOut++ += (q31_t) * px++ * coeff;
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*pScratchOut++ += (q31_t) * px++ * coeff;
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*pScratchOut++ += (q31_t) * px++ * coeff;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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* compute the remaining samples */
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blkCnt = blockSize % 0x4U;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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*pScratchOut++ += (q31_t) * px++ * coeff;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* All the output values are in pScratchOut buffer.
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Convert them into 1.15 format, saturate and store in the destination buffer. */
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/* Loop over the blockSize. */
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blkCnt = blockSize >> 2;
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while (blkCnt > 0U)
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{
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in1 = *pScr2++;
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in2 = *pScr2++;
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#ifndef ARM_MATH_BIG_ENDIAN
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*__SIMD32(pOut)++ =
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__PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
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16);
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#else
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*__SIMD32(pOut)++ =
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__PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
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16);
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#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
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in1 = *pScr2++;
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in2 = *pScr2++;
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#ifndef ARM_MATH_BIG_ENDIAN
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*__SIMD32(pOut)++ =
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__PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
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16);
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#else
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*__SIMD32(pOut)++ =
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__PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
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16);
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#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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remaining samples are processed in the below loop */
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blkCnt = blockSize % 0x4U;
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while (blkCnt > 0U)
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{
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*pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
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blkCnt--;
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}
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#else
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/* Run the below code for Cortex-M0 */
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/* BlockSize of Input samples are copied into the state buffer */
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/* StateIndex points to the starting position to write in the state buffer */
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arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);
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/* Loop over the number of taps. */
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tapCnt = numTaps;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q15(py, delaySize, &readIndex, 1,
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pb, pb, blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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blkCnt = blockSize;
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while (blkCnt > 0U)
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{
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/* Perform multiplication and store in the scratch buffer */
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*pScratchOut++ = ((q31_t) * px++ * coeff);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Loop over the number of taps. */
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tapCnt = (uint32_t) numTaps - 2U;
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while (tapCnt > 0U)
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{
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q15(py, delaySize, &readIndex, 1,
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pb, pb, blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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blkCnt = blockSize;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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*pScratchOut++ += (q31_t) * px++ * coeff;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if (readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Decrement the tap loop counter */
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tapCnt--;
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}
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/* Compute last tap without the final read of pTapDelay */
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_q15(py, delaySize, &readIndex, 1,
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pb, pb, blockSize, 1, blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pScratchOut = pScr2;
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blkCnt = blockSize;
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while (blkCnt > 0U)
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{
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/* Perform Multiply-Accumulate */
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*pScratchOut++ += (q31_t) * px++ * coeff;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* All the output values are in pScratchOut buffer.
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Convert them into 1.15 format, saturate and store in the destination buffer. */
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/* Loop over the blockSize. */
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blkCnt = blockSize;
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while (blkCnt > 0U)
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{
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*pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
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blkCnt--;
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}
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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_Sparse group
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*/
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