393 lines
12 KiB
C
393 lines
12 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_biquad_cascade_df1_q31.c
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* Description: Processing function for the Q31 Biquad cascade filter
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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 BiquadCascadeDF1
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* @{
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*/
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/**
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* @brief Processing function for the Q31 Biquad cascade filter.
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* @param[in] *S points to an instance of the Q31 Biquad cascade 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 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 64-bit accumulator.
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* The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
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* Thus, if the accumulator result overflows it wraps around rather than clip.
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* In order to avoid overflows completely the input signal must be scaled down by 2 bits and lie in the range [-0.25 +0.25).
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* After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to
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* 1.31 format by discarding the low 32 bits.
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*
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* \par
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* Refer to the function <code>arm_biquad_cascade_df1_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
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*/
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void arm_biquad_cascade_df1_q31(
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const arm_biquad_casd_df1_inst_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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q63_t acc; /* accumulator */
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uint32_t uShift = ((uint32_t) S->postShift + 1U);
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uint32_t lShift = 32U - uShift; /* Shift to be applied to the output */
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q31_t *pIn = pSrc; /* input pointer initialization */
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q31_t *pOut = pDst; /* output pointer initialization */
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q31_t *pState = S->pState; /* pState pointer initialization */
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q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */
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q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
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q31_t b0, b1, b2, a1, a2; /* Filter coefficients */
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q31_t Xn; /* temporary input */
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uint32_t sample, stage = S->numStages; /* loop counters */
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#if defined (ARM_MATH_DSP)
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q31_t acc_l, acc_h; /* temporary output variables */
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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do
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{
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/* Reading the coefficients */
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b0 = *pCoeffs++;
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b1 = *pCoeffs++;
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b2 = *pCoeffs++;
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a1 = *pCoeffs++;
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a2 = *pCoeffs++;
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/* Reading the state values */
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Xn1 = pState[0];
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Xn2 = pState[1];
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Yn1 = pState[2];
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Yn2 = pState[3];
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/* Apply loop unrolling and compute 4 output values simultaneously. */
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/* The variable acc hold output values that are being computed:
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*
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* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
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*/
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sample = blockSize >> 2U;
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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** a second loop below computes the remaining 1 to 3 samples. */
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while (sample > 0U)
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{
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/* Read the input */
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Xn = *pIn++;
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/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
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/* acc = b0 * x[n] */
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acc = (q63_t) b0 *Xn;
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/* acc += b1 * x[n-1] */
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acc += (q63_t) b1 *Xn1;
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/* acc += b[2] * x[n-2] */
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acc += (q63_t) b2 *Xn2;
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/* acc += a1 * y[n-1] */
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acc += (q63_t) a1 *Yn1;
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/* acc += a2 * y[n-2] */
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acc += (q63_t) a2 *Yn2;
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/* The result is converted to 1.31 , Yn2 variable is reused */
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/* Calc lower part of acc */
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acc_l = acc & 0xffffffff;
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/* Calc upper part of acc */
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acc_h = (acc >> 32) & 0xffffffff;
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/* Apply shift for lower part of acc and upper part of acc */
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Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
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/* Store the output in the destination buffer. */
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*pOut++ = Yn2;
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/* Read the second input */
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Xn2 = *pIn++;
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/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
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/* acc = b0 * x[n] */
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acc = (q63_t) b0 *Xn2;
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/* acc += b1 * x[n-1] */
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acc += (q63_t) b1 *Xn;
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/* acc += b[2] * x[n-2] */
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acc += (q63_t) b2 *Xn1;
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/* acc += a1 * y[n-1] */
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acc += (q63_t) a1 *Yn2;
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/* acc += a2 * y[n-2] */
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acc += (q63_t) a2 *Yn1;
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/* The result is converted to 1.31, Yn1 variable is reused */
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/* Calc lower part of acc */
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acc_l = acc & 0xffffffff;
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/* Calc upper part of acc */
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acc_h = (acc >> 32) & 0xffffffff;
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/* Apply shift for lower part of acc and upper part of acc */
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Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
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/* Store the output in the destination buffer. */
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*pOut++ = Yn1;
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/* Read the third input */
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Xn1 = *pIn++;
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/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
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/* acc = b0 * x[n] */
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acc = (q63_t) b0 *Xn1;
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/* acc += b1 * x[n-1] */
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acc += (q63_t) b1 *Xn2;
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/* acc += b[2] * x[n-2] */
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acc += (q63_t) b2 *Xn;
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/* acc += a1 * y[n-1] */
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acc += (q63_t) a1 *Yn1;
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/* acc += a2 * y[n-2] */
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acc += (q63_t) a2 *Yn2;
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/* The result is converted to 1.31, Yn2 variable is reused */
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/* Calc lower part of acc */
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acc_l = acc & 0xffffffff;
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/* Calc upper part of acc */
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acc_h = (acc >> 32) & 0xffffffff;
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/* Apply shift for lower part of acc and upper part of acc */
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Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
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/* Store the output in the destination buffer. */
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*pOut++ = Yn2;
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/* Read the forth input */
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Xn = *pIn++;
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/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
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/* acc = b0 * x[n] */
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acc = (q63_t) b0 *Xn;
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/* acc += b1 * x[n-1] */
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acc += (q63_t) b1 *Xn1;
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/* acc += b[2] * x[n-2] */
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acc += (q63_t) b2 *Xn2;
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/* acc += a1 * y[n-1] */
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acc += (q63_t) a1 *Yn2;
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/* acc += a2 * y[n-2] */
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acc += (q63_t) a2 *Yn1;
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/* The result is converted to 1.31, Yn1 variable is reused */
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/* Calc lower part of acc */
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acc_l = acc & 0xffffffff;
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/* Calc upper part of acc */
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acc_h = (acc >> 32) & 0xffffffff;
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/* Apply shift for lower part of acc and upper part of acc */
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Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
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/* Every time after the output is computed state should be updated. */
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/* The states should be updated as: */
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/* Xn2 = Xn1 */
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/* Xn1 = Xn */
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/* Yn2 = Yn1 */
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/* Yn1 = acc */
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Xn2 = Xn1;
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Xn1 = Xn;
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/* Store the output in the destination buffer. */
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*pOut++ = Yn1;
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/* decrement the loop counter */
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sample--;
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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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sample = (blockSize & 0x3U);
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while (sample > 0U)
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{
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/* Read the input */
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Xn = *pIn++;
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/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
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/* acc = b0 * x[n] */
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acc = (q63_t) b0 *Xn;
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/* acc += b1 * x[n-1] */
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acc += (q63_t) b1 *Xn1;
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/* acc += b[2] * x[n-2] */
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acc += (q63_t) b2 *Xn2;
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/* acc += a1 * y[n-1] */
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acc += (q63_t) a1 *Yn1;
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/* acc += a2 * y[n-2] */
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acc += (q63_t) a2 *Yn2;
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/* The result is converted to 1.31 */
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acc = acc >> lShift;
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/* Every time after the output is computed state should be updated. */
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/* The states should be updated as: */
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/* Xn2 = Xn1 */
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/* Xn1 = Xn */
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/* Yn2 = Yn1 */
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/* Yn1 = acc */
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Xn2 = Xn1;
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Xn1 = Xn;
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Yn2 = Yn1;
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Yn1 = (q31_t) acc;
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/* Store the output in the destination buffer. */
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*pOut++ = (q31_t) acc;
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/* decrement the loop counter */
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sample--;
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}
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/* The first stage goes from the input buffer to the output buffer. */
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/* Subsequent stages occur in-place in the output buffer */
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pIn = pDst;
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/* Reset to destination pointer */
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pOut = pDst;
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/* Store the updated state variables back into the pState array */
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*pState++ = Xn1;
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*pState++ = Xn2;
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*pState++ = Yn1;
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*pState++ = Yn2;
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} while (--stage);
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#else
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/* Run the below code for Cortex-M0 */
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do
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{
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/* Reading the coefficients */
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b0 = *pCoeffs++;
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b1 = *pCoeffs++;
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b2 = *pCoeffs++;
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a1 = *pCoeffs++;
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a2 = *pCoeffs++;
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/* Reading the state values */
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Xn1 = pState[0];
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Xn2 = pState[1];
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Yn1 = pState[2];
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Yn2 = pState[3];
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/* The variables acc holds the output value that is computed:
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* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
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*/
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sample = blockSize;
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while (sample > 0U)
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{
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/* Read the input */
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Xn = *pIn++;
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/* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
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/* acc = b0 * x[n] */
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acc = (q63_t) b0 *Xn;
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/* acc += b1 * x[n-1] */
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acc += (q63_t) b1 *Xn1;
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/* acc += b[2] * x[n-2] */
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acc += (q63_t) b2 *Xn2;
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/* acc += a1 * y[n-1] */
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acc += (q63_t) a1 *Yn1;
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/* acc += a2 * y[n-2] */
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acc += (q63_t) a2 *Yn2;
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/* The result is converted to 1.31 */
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acc = acc >> lShift;
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/* Every time after the output is computed state should be updated. */
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/* The states should be updated as: */
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/* Xn2 = Xn1 */
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/* Xn1 = Xn */
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/* Yn2 = Yn1 */
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/* Yn1 = acc */
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Xn2 = Xn1;
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Xn1 = Xn;
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Yn2 = Yn1;
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Yn1 = (q31_t) acc;
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/* Store the output in the destination buffer. */
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*pOut++ = (q31_t) acc;
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/* decrement the loop counter */
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sample--;
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}
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/* The first stage goes from the input buffer to the output buffer. */
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/* Subsequent stages occur in-place in the output buffer */
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pIn = pDst;
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/* Reset to destination pointer */
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pOut = pDst;
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/* Store the updated state variables back into the pState array */
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*pState++ = Xn1;
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*pState++ = Xn2;
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*pState++ = Yn1;
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*pState++ = Yn2;
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} while (--stage);
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#endif /* #if defined (ARM_MATH_DSP) */
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}
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/**
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* @} end of BiquadCascadeDF1 group
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*/
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