/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_fir_lattice_q31.c
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* Description: Q31 FIR lattice 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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* @ingroup groupFilters
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*/
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/**
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* @addtogroup FIR_Lattice
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* @{
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*/
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/**
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* @brief Processing function for the Q31 FIR lattice filter.
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* @param[in] *S points to an instance of the Q31 FIR lattice 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] blockSize number of samples to process.
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* @return none.
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*
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* @details
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* <b>Scaling and Overflow Behavior:</b>
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* In order to avoid overflows the input signal must be scaled down by 2*log2(numStages) bits.
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*/
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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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void arm_fir_lattice_q31(
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const arm_fir_lattice_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pDst,
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uint32_t blockSize)
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{
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q31_t *pState; /* State pointer */
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q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q31_t *px; /* temporary state pointer */
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q31_t *pk; /* temporary coefficient pointer */
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q31_t fcurr1, fnext1, gcurr1 = 0, gnext1; /* temporary variables for first sample in loop unrolling */
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q31_t fcurr2, fnext2, gnext2; /* temporary variables for second sample in loop unrolling */
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uint32_t numStages = S->numStages; /* Length of the filter */
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uint32_t blkCnt, stageCnt; /* temporary variables for counts */
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q31_t k;
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pState = &S->pState[0];
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blkCnt = blockSize >> 1U;
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/* First part of the processing with loop unrolling. Compute 2 outputs at a time.
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a second loop below computes the remaining 1 sample. */
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while (blkCnt > 0U)
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{
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/* f0(n) = x(n) */
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fcurr1 = *pSrc++;
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/* f0(n) = x(n) */
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fcurr2 = *pSrc++;
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/* Initialize coeff pointer */
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pk = (pCoeffs);
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/* Initialize state pointer */
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px = pState;
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/* read g0(n - 1) from state buffer */
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gcurr1 = *px;
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/* Read the reflection coefficient */
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k = *pk++;
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/* for sample 1 processing */
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/* f1(n) = f0(n) + K1 * g0(n-1) */
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fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
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fnext1 = fcurr1 + (fnext1 << 1U);
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gnext1 = gcurr1 + (gnext1 << 1U);
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/* for sample 1 processing */
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/* f1(n) = f0(n) + K1 * g0(n-1) */
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fnext2 = (q31_t) (((q63_t) fcurr1 * k) >> 32);
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32);
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fnext2 = fcurr2 + (fnext2 << 1U);
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gnext2 = fcurr1 + (gnext2 << 1U);
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/* save g1(n) in state buffer */
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*px++ = fcurr2;
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr1 = fnext1;
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fcurr2 = fnext2;
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stageCnt = (numStages - 1U);
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/* stage loop */
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while (stageCnt > 0U)
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{
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/* Read the reflection coefficient */
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k = *pk++;
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/* read g2(n) from state buffer */
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gcurr1 = *px;
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/* save g1(n) in state buffer */
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*px++ = gnext2;
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/* Sample processing for K2, K3.... */
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/* f2(n) = f1(n) + K2 * g1(n-1) */
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fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
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fnext2 = (q31_t) (((q63_t) gnext1 * k) >> 32);
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fnext1 = fcurr1 + (fnext1 << 1U);
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fnext2 = fcurr2 + (fnext2 << 1U);
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/* g2(n) = f1(n) * K2 + g1(n-1) */
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gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32);
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gnext2 = gnext1 + (gnext2 << 1U);
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/* g2(n) = f1(n) * K2 + g1(n-1) */
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gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
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gnext1 = gcurr1 + (gnext1 << 1U);
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr1 = fnext1;
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fcurr2 = fnext2;
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stageCnt--;
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}
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/* y(n) = fN(n) */
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*pDst++ = fcurr1;
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*pDst++ = fcurr2;
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x2U;
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while (blkCnt > 0U)
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{
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/* f0(n) = x(n) */
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fcurr1 = *pSrc++;
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/* Initialize coeff pointer */
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pk = (pCoeffs);
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/* Initialize state pointer */
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px = pState;
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/* read g0(n - 1) from state buffer */
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gcurr1 = *px;
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/* Read the reflection coefficient */
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k = *pk++;
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/* for sample 1 processing */
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/* f1(n) = f0(n) + K1 * g0(n-1) */
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fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
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fnext1 = fcurr1 + (fnext1 << 1U);
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
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gnext1 = gcurr1 + (gnext1 << 1U);
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/* save g1(n) in state buffer */
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*px++ = fcurr1;
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr1 = fnext1;
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stageCnt = (numStages - 1U);
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/* stage loop */
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while (stageCnt > 0U)
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{
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/* Read the reflection coefficient */
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k = *pk++;
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/* read g2(n) from state buffer */
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gcurr1 = *px;
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/* save g1(n) in state buffer */
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*px++ = gnext1;
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/* Sample processing for K2, K3.... */
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/* f2(n) = f1(n) + K2 * g1(n-1) */
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fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
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fnext1 = fcurr1 + (fnext1 << 1U);
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/* g2(n) = f1(n) * K2 + g1(n-1) */
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gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
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gnext1 = gcurr1 + (gnext1 << 1U);
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr1 = fnext1;
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stageCnt--;
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}
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/* y(n) = fN(n) */
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*pDst++ = fcurr1;
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blkCnt--;
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}
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}
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#else
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/* Run the below code for Cortex-M0 */
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void arm_fir_lattice_q31(
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const arm_fir_lattice_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pDst,
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uint32_t blockSize)
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{
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q31_t *pState; /* State pointer */
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q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q31_t *px; /* temporary state pointer */
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q31_t *pk; /* temporary coefficient pointer */
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q31_t fcurr, fnext, gcurr, gnext; /* temporary variables */
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uint32_t numStages = S->numStages; /* Length of the filter */
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uint32_t blkCnt, stageCnt; /* temporary variables for counts */
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pState = &S->pState[0];
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blkCnt = blockSize;
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while (blkCnt > 0U)
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{
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/* f0(n) = x(n) */
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fcurr = *pSrc++;
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/* Initialize coeff pointer */
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pk = (pCoeffs);
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/* Initialize state pointer */
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px = pState;
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/* read g0(n-1) from state buffer */
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gcurr = *px;
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/* for sample 1 processing */
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/* f1(n) = f0(n) + K1 * g0(n-1) */
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fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr;
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr;
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/* save g1(n) in state buffer */
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*px++ = fcurr;
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr = fnext;
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stageCnt = (numStages - 1U);
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/* stage loop */
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while (stageCnt > 0U)
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{
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/* read g2(n) from state buffer */
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gcurr = *px;
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/* save g1(n) in state buffer */
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*px++ = gnext;
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/* Sample processing for K2, K3.... */
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/* f2(n) = f1(n) + K2 * g1(n-1) */
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fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr;
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/* g2(n) = f1(n) * K2 + g1(n-1) */
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gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr;
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr = fnext;
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stageCnt--;
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}
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/* y(n) = fN(n) */
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*pDst++ = fcurr;
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blkCnt--;
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}
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}
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#endif /* #if defined (ARM_MATH_DSP) */
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/**
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* @} end of FIR_Lattice group
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*/
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