/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_fir_decimate_q15.c
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* Description: Q15 FIR Decimator
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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_decimate
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* @{
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*/
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/**
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* @brief Processing function for the Q15 FIR decimator.
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* @param[in] *S points to an instance of the Q15 FIR decimator 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 location where the output result is written.
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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 a 64-bit internal accumulator.
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* Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
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* The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
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* There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
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* After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits.
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* Lastly, the accumulator is saturated to yield a result in 1.15 format.
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*
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* \par
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* Refer to the function <code>arm_fir_decimate_fast_q15()</code> for a faster but less precise implementation of this function for Cortex-M3 and Cortex-M4.
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*/
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#if defined (ARM_MATH_DSP)
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#ifndef UNALIGNED_SUPPORT_DISABLE
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void arm_fir_decimate_q15(
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const arm_fir_decimate_instance_q15 * S,
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q15_t * pSrc,
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q15_t * pDst,
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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 *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q15_t *pStateCurnt; /* Points to the current sample of the state */
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q15_t *px; /* Temporary pointer for state buffer */
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q15_t *pb; /* Temporary pointer coefficient buffer */
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q31_t x0, x1, c0, c1; /* Temporary variables to hold state and coefficient values */
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q63_t sum0; /* Accumulators */
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q63_t acc0, acc1;
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q15_t *px0, *px1;
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uint32_t blkCntN3;
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uint32_t numTaps = S->numTaps; /* Number of taps */
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uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M; /* Loop counters */
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/* S->pState buffer contains previous frame (numTaps - 1) samples */
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/* pStateCurnt points to the location where the new input data should be written */
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pStateCurnt = S->pState + (numTaps - 1U);
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/* Total number of output samples to be computed */
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blkCnt = outBlockSize / 2;
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blkCntN3 = outBlockSize - (2 * blkCnt);
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while (blkCnt > 0U)
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{
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/* Copy decimation factor number of new input samples into the state buffer */
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i = 2 * S->M;
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do
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{
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*pStateCurnt++ = *pSrc++;
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} while (--i);
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/* Set accumulator to zero */
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acc0 = 0;
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acc1 = 0;
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/* Initialize state pointer */
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px0 = pState;
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px1 = pState + S->M;
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/* Initialize coeff pointer */
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pb = pCoeffs;
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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/* Loop over the number of taps. Unroll by a factor of 4.
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** Repeat until we've computed numTaps-4 coefficients. */
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while (tapCnt > 0U)
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{
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/* Read the Read b[numTaps-1] and b[numTaps-2] coefficients */
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c0 = *__SIMD32(pb)++;
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/* Read x[n-numTaps-1] and x[n-numTaps-2]sample */
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x0 = *__SIMD32(px0)++;
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x1 = *__SIMD32(px1)++;
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/* Perform the multiply-accumulate */
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acc0 = __SMLALD(x0, c0, acc0);
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acc1 = __SMLALD(x1, c0, acc1);
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/* Read the b[numTaps-3] and b[numTaps-4] coefficient */
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c0 = *__SIMD32(pb)++;
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/* Read x[n-numTaps-2] and x[n-numTaps-3] sample */
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x0 = *__SIMD32(px0)++;
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x1 = *__SIMD32(px1)++;
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/* Perform the multiply-accumulate */
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acc0 = __SMLALD(x0, c0, acc0);
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acc1 = __SMLALD(x1, c0, acc1);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the filter length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = numTaps % 0x4U;
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while (tapCnt > 0U)
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{
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/* Read coefficients */
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c0 = *pb++;
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/* Fetch 1 state variable */
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x0 = *px0++;
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x1 = *px1++;
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/* Perform the multiply-accumulate */
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acc0 = __SMLALD(x0, c0, acc0);
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acc1 = __SMLALD(x1, c0, acc1);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Advance the state pointer by the decimation factor
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* to process the next group of decimation factor number samples */
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pState = pState + S->M * 2;
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/* Store filter output, smlad returns the values in 2.14 format */
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/* so downsacle by 15 to get output in 1.15 */
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*pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16));
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*pDst++ = (q15_t) (__SSAT((acc1 >> 15), 16));
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/* Decrement the loop counter */
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blkCnt--;
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}
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while (blkCntN3 > 0U)
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{
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/* Copy decimation factor number of new input samples into the state buffer */
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i = S->M;
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do
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{
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*pStateCurnt++ = *pSrc++;
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} while (--i);
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/*Set sum to zero */
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sum0 = 0;
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/* Initialize state pointer */
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px = pState;
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/* Initialize coeff pointer */
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pb = pCoeffs;
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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/* Loop over the number of taps. Unroll by a factor of 4.
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** Repeat until we've computed numTaps-4 coefficients. */
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while (tapCnt > 0U)
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{
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/* Read the Read b[numTaps-1] and b[numTaps-2] coefficients */
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c0 = *__SIMD32(pb)++;
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/* Read x[n-numTaps-1] and x[n-numTaps-2]sample */
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x0 = *__SIMD32(px)++;
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/* Read the b[numTaps-3] and b[numTaps-4] coefficient */
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c1 = *__SIMD32(pb)++;
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/* Perform the multiply-accumulate */
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sum0 = __SMLALD(x0, c0, sum0);
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/* Read x[n-numTaps-2] and x[n-numTaps-3] sample */
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x0 = *__SIMD32(px)++;
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/* Perform the multiply-accumulate */
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sum0 = __SMLALD(x0, c1, sum0);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the filter length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = numTaps % 0x4U;
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while (tapCnt > 0U)
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{
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/* Read coefficients */
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c0 = *pb++;
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/* Fetch 1 state variable */
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x0 = *px++;
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/* Perform the multiply-accumulate */
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sum0 = __SMLALD(x0, c0, sum0);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Advance the state pointer by the decimation factor
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* to process the next group of decimation factor number samples */
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pState = pState + S->M;
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/* Store filter output, smlad returns the values in 2.14 format */
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/* so downsacle by 15 to get output in 1.15 */
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*pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
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/* Decrement the loop counter */
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blkCntN3--;
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}
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/* Processing is complete.
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** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
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** This prepares the state buffer for the next function call. */
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/* Points to the start of the state buffer */
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pStateCurnt = S->pState;
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i = (numTaps - 1U) >> 2U;
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/* copy data */
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while (i > 0U)
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{
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*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
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*__SIMD32(pStateCurnt)++ = *__SIMD32(pState)++;
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/* Decrement the loop counter */
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i--;
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}
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i = (numTaps - 1U) % 0x04U;
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/* copy data */
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while (i > 0U)
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{
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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i--;
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}
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}
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#else
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void arm_fir_decimate_q15(
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const arm_fir_decimate_instance_q15 * S,
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q15_t * pSrc,
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q15_t * pDst,
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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 *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q15_t *pStateCurnt; /* Points to the current sample of the state */
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q15_t *px; /* Temporary pointer for state buffer */
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q15_t *pb; /* Temporary pointer coefficient buffer */
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q15_t x0, x1, c0; /* Temporary variables to hold state and coefficient values */
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q63_t sum0; /* Accumulators */
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q63_t acc0, acc1;
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q15_t *px0, *px1;
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uint32_t blkCntN3;
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uint32_t numTaps = S->numTaps; /* Number of taps */
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uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M; /* Loop counters */
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/* S->pState buffer contains previous frame (numTaps - 1) samples */
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/* pStateCurnt points to the location where the new input data should be written */
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pStateCurnt = S->pState + (numTaps - 1U);
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/* Total number of output samples to be computed */
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blkCnt = outBlockSize / 2;
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blkCntN3 = outBlockSize - (2 * blkCnt);
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while (blkCnt > 0U)
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{
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/* Copy decimation factor number of new input samples into the state buffer */
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i = 2 * S->M;
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do
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{
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*pStateCurnt++ = *pSrc++;
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} while (--i);
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/* Set accumulator to zero */
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acc0 = 0;
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acc1 = 0;
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/* Initialize state pointer */
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px0 = pState;
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px1 = pState + S->M;
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/* Initialize coeff pointer */
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pb = pCoeffs;
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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/* Loop over the number of taps. Unroll by a factor of 4.
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** Repeat until we've computed numTaps-4 coefficients. */
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while (tapCnt > 0U)
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{
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/* Read the Read b[numTaps-1] coefficients */
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c0 = *pb++;
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/* Read x[n-numTaps-1] for sample 0 and for sample 1 */
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x0 = *px0++;
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x1 = *px1++;
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/* Perform the multiply-accumulate */
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acc0 += x0 * c0;
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acc1 += x1 * c0;
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/* Read the b[numTaps-2] coefficient */
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c0 = *pb++;
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/* Read x[n-numTaps-2] for sample 0 and sample 1 */
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x0 = *px0++;
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x1 = *px1++;
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/* Perform the multiply-accumulate */
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acc0 += x0 * c0;
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acc1 += x1 * c0;
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/* Read the b[numTaps-3] coefficients */
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c0 = *pb++;
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/* Read x[n-numTaps-3] for sample 0 and sample 1 */
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x0 = *px0++;
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x1 = *px1++;
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/* Perform the multiply-accumulate */
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acc0 += x0 * c0;
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acc1 += x1 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *pb++;
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/* Read x[n-numTaps-4] for sample 0 and sample 1 */
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x0 = *px0++;
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x1 = *px1++;
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/* Perform the multiply-accumulate */
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acc0 += x0 * c0;
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acc1 += x1 * c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the filter length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = numTaps % 0x4U;
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while (tapCnt > 0U)
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{
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/* Read coefficients */
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c0 = *pb++;
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/* Fetch 1 state variable */
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x0 = *px0++;
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x1 = *px1++;
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/* Perform the multiply-accumulate */
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acc0 += x0 * c0;
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acc1 += x1 * c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Advance the state pointer by the decimation factor
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* to process the next group of decimation factor number samples */
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pState = pState + S->M * 2;
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/* Store filter output, smlad returns the values in 2.14 format */
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/* so downsacle by 15 to get output in 1.15 */
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*pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16));
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*pDst++ = (q15_t) (__SSAT((acc1 >> 15), 16));
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/* Decrement the loop counter */
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blkCnt--;
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}
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while (blkCntN3 > 0U)
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{
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/* Copy decimation factor number of new input samples into the state buffer */
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i = S->M;
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do
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{
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*pStateCurnt++ = *pSrc++;
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} while (--i);
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/*Set sum to zero */
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sum0 = 0;
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/* Initialize state pointer */
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px = pState;
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/* Initialize coeff pointer */
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pb = pCoeffs;
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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/* Loop over the number of taps. Unroll by a factor of 4.
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** Repeat until we've computed numTaps-4 coefficients. */
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while (tapCnt > 0U)
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{
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/* Read the Read b[numTaps-1] coefficients */
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c0 = *pb++;
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/* Read x[n-numTaps-1] and sample */
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x0 = *px++;
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/* Perform the multiply-accumulate */
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sum0 += x0 * c0;
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/* Read the b[numTaps-2] coefficient */
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c0 = *pb++;
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/* Read x[n-numTaps-2] and sample */
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x0 = *px++;
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/* Perform the multiply-accumulate */
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sum0 += x0 * c0;
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/* Read the b[numTaps-3] coefficients */
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c0 = *pb++;
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/* Read x[n-numTaps-3] sample */
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x0 = *px++;
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/* Perform the multiply-accumulate */
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sum0 += x0 * c0;
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/* Read the b[numTaps-4] coefficient */
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c0 = *pb++;
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/* Read x[n-numTaps-4] sample */
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x0 = *px++;
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/* Perform the multiply-accumulate */
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sum0 += x0 * c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the filter length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = numTaps % 0x4U;
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while (tapCnt > 0U)
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{
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/* Read coefficients */
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c0 = *pb++;
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/* Fetch 1 state variable */
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x0 = *px++;
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/* Perform the multiply-accumulate */
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sum0 += x0 * c0;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Advance the state pointer by the decimation factor
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* to process the next group of decimation factor number samples */
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pState = pState + S->M;
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/* Store filter output, smlad returns the values in 2.14 format */
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/* so downsacle by 15 to get output in 1.15 */
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*pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
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/* Decrement the loop counter */
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blkCntN3--;
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}
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/* Processing is complete.
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** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
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** This prepares the state buffer for the next function call. */
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/* Points to the start of the state buffer */
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pStateCurnt = S->pState;
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i = (numTaps - 1U) >> 2U;
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/* copy data */
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while (i > 0U)
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{
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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i--;
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}
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i = (numTaps - 1U) % 0x04U;
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/* copy data */
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while (i > 0U)
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{
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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i--;
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}
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}
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#endif /* #ifndef UNALIGNED_SUPPORT_DISABLE */
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#else
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void arm_fir_decimate_q15(
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const arm_fir_decimate_instance_q15 * S,
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q15_t * pSrc,
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q15_t * pDst,
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uint32_t blockSize)
|
{
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q15_t *pState = S->pState; /* State pointer */
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q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
|
q15_t *pStateCurnt; /* Points to the current sample of the state */
|
q15_t *px; /* Temporary pointer for state buffer */
|
q15_t *pb; /* Temporary pointer coefficient buffer */
|
q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
|
q63_t sum0; /* Accumulators */
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uint32_t numTaps = S->numTaps; /* Number of taps */
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uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M; /* Loop counters */
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|
|
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/* Run the below code for Cortex-M0 */
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/* S->pState buffer contains previous frame (numTaps - 1) samples */
|
/* pStateCurnt points to the location where the new input data should be written */
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pStateCurnt = S->pState + (numTaps - 1U);
|
|
/* Total number of output samples to be computed */
|
blkCnt = outBlockSize;
|
|
while (blkCnt > 0U)
|
{
|
/* Copy decimation factor number of new input samples into the state buffer */
|
i = S->M;
|
|
do
|
{
|
*pStateCurnt++ = *pSrc++;
|
|
} while (--i);
|
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/*Set sum to zero */
|
sum0 = 0;
|
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/* Initialize state pointer */
|
px = pState;
|
|
/* Initialize coeff pointer */
|
pb = pCoeffs;
|
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tapCnt = numTaps;
|
|
while (tapCnt > 0U)
|
{
|
/* Read coefficients */
|
c0 = *pb++;
|
|
/* Fetch 1 state variable */
|
x0 = *px++;
|
|
/* Perform the multiply-accumulate */
|
sum0 += (q31_t) x0 *c0;
|
|
/* Decrement the loop counter */
|
tapCnt--;
|
}
|
|
/* Advance the state pointer by the decimation factor
|
* to process the next group of decimation factor number samples */
|
pState = pState + S->M;
|
|
/*Store filter output , smlad will return the values in 2.14 format */
|
/* so downsacle by 15 to get output in 1.15 */
|
*pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16));
|
|
/* Decrement the loop counter */
|
blkCnt--;
|
}
|
|
/* Processing is complete.
|
** Now copy the last numTaps - 1 samples to the start of the state buffer.
|
** This prepares the state buffer for the next function call. */
|
|
/* Points to the start of the state buffer */
|
pStateCurnt = S->pState;
|
|
i = numTaps - 1U;
|
|
/* copy data */
|
while (i > 0U)
|
{
|
*pStateCurnt++ = *pState++;
|
|
/* Decrement the loop counter */
|
i--;
|
}
|
|
|
}
|
#endif /* #if defined (ARM_MATH_DSP) */
|
|
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/**
|
* @} end of FIR_decimate group
|
*/
|
