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398 lines
12 KiB
C
398 lines
12 KiB
C
/* ----------------------------------------------------------------------
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* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
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*
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* $Date: 19. March 2015
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* $Revision: V.1.4.5
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*
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* Project: CMSIS DSP Library
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* Title: arm_fir_q7.c
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*
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* Description: Q7 FIR filter processing function.
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*
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* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* - Neither the name of ARM LIMITED nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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* -------------------------------------------------------------------- */
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#include "arm_math.h"
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/**
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* @ingroup groupFilters
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*/
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/**
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* @addtogroup FIR
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* @{
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*/
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/**
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* @param[in] *S points to an instance of the Q7 FIR filter 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 a 32-bit internal accumulator.
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* Both coefficients and state variables are represented in 1.7 format and multiplications yield a 2.14 result.
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* The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 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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* The accumulator is converted to 18.7 format by discarding the low 7 bits.
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* Finally, the result is truncated to 1.7 format.
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*/
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void arm_fir_q7(
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const arm_fir_instance_q7 * S,
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q7_t * pSrc,
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q7_t * pDst,
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uint32_t blockSize)
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{
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#ifndef ARM_MATH_CM0_FAMILY
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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q7_t *pState = S->pState; /* State pointer */
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q7_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q7_t *pStateCurnt; /* Points to the current sample of the state */
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q7_t x0, x1, x2, x3; /* Temporary variables to hold state */
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q7_t c0; /* Temporary variable to hold coefficient value */
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q7_t *px; /* Temporary pointer for state */
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q7_t *pb; /* Temporary pointer for coefficient buffer */
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q31_t acc0, acc1, acc2, acc3; /* Accumulators */
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uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
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uint32_t i, tapCnt, blkCnt; /* Loop counters */
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/* S->pState points to state array which 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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/* Apply loop unrolling and compute 4 output values simultaneously.
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* The variables acc0 ... acc3 hold output values that are being computed:
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*
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* acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]
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* acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]
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* acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]
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* acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3]
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*/
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blkCnt = blockSize >> 2;
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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(blkCnt > 0u)
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{
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/* Copy four new input samples into the state buffer */
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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*pStateCurnt++ = *pSrc++;
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/* Set all accumulators to zero */
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acc0 = 0;
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acc1 = 0;
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acc2 = 0;
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acc3 = 0;
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/* Initialize state pointer */
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px = pState;
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/* Initialize coefficient pointer */
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pb = pCoeffs;
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/* Read the first three samples from the state buffer:
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* x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */
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x0 = *(px++);
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x1 = *(px++);
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x2 = *(px++);
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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i = tapCnt;
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while(i > 0u)
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{
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/* Read the b[numTaps] coefficient */
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c0 = *pb;
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/* Read x[n-numTaps-3] sample */
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x3 = *px;
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/* acc0 += b[numTaps] * x[n-numTaps] */
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acc0 += ((q15_t) x0 * c0);
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/* acc1 += b[numTaps] * x[n-numTaps-1] */
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acc1 += ((q15_t) x1 * c0);
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/* acc2 += b[numTaps] * x[n-numTaps-2] */
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acc2 += ((q15_t) x2 * c0);
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/* acc3 += b[numTaps] * x[n-numTaps-3] */
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acc3 += ((q15_t) x3 * c0);
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/* Read the b[numTaps-1] coefficient */
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c0 = *(pb + 1u);
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/* Read x[n-numTaps-4] sample */
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x0 = *(px + 1u);
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/* Perform the multiply-accumulates */
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acc0 += ((q15_t) x1 * c0);
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acc1 += ((q15_t) x2 * c0);
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acc2 += ((q15_t) x3 * c0);
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acc3 += ((q15_t) x0 * c0);
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/* Read the b[numTaps-2] coefficient */
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c0 = *(pb + 2u);
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/* Read x[n-numTaps-5] sample */
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x1 = *(px + 2u);
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/* Perform the multiply-accumulates */
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acc0 += ((q15_t) x2 * c0);
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acc1 += ((q15_t) x3 * c0);
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acc2 += ((q15_t) x0 * c0);
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acc3 += ((q15_t) x1 * c0);
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/* Read the b[numTaps-3] coefficients */
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c0 = *(pb + 3u);
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/* Read x[n-numTaps-6] sample */
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x2 = *(px + 3u);
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/* Perform the multiply-accumulates */
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acc0 += ((q15_t) x3 * c0);
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acc1 += ((q15_t) x0 * c0);
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acc2 += ((q15_t) x1 * c0);
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acc3 += ((q15_t) x2 * c0);
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/* update coefficient pointer */
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pb += 4u;
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px += 4u;
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/* Decrement the loop counter */
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i--;
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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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i = numTaps - (tapCnt * 4u);
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while(i > 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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x3 = *(px++);
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/* Perform the multiply-accumulates */
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acc0 += ((q15_t) x0 * c0);
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acc1 += ((q15_t) x1 * c0);
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acc2 += ((q15_t) x2 * c0);
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acc3 += ((q15_t) x3 * c0);
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/* Reuse the present sample states for next sample */
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x0 = x1;
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x1 = x2;
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x2 = x3;
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/* Decrement the loop counter */
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i--;
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}
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/* Advance the state pointer by 4 to process the next group of 4 samples */
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pState = pState + 4;
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/* The results in the 4 accumulators are in 2.62 format. Convert to 1.31
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** Then store the 4 outputs in the destination buffer. */
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acc0 = __SSAT((acc0 >> 7u), 8);
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*pDst++ = acc0;
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acc1 = __SSAT((acc1 >> 7u), 8);
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*pDst++ = acc1;
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acc2 = __SSAT((acc2 >> 7u), 8);
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*pDst++ = acc2;
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acc3 = __SSAT((acc3 >> 7u), 8);
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*pDst++ = acc3;
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/* Decrement the samples loop counter */
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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 % 4u;
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while(blkCnt > 0u)
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{
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/* Copy one sample at a time into state buffer */
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*pStateCurnt++ = *pSrc++;
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/* Set the accumulator to zero */
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acc0 = 0;
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/* Initialize state pointer */
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px = pState;
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/* Initialize Coefficient pointer */
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pb = (pCoeffs);
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i = numTaps;
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/* Perform the multiply-accumulates */
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do
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{
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acc0 += (q15_t) * (px++) * (*(pb++));
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i--;
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} while(i > 0u);
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/* The result is in 2.14 format. Convert to 1.7
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** Then store the output in the destination buffer. */
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*pDst++ = __SSAT((acc0 >> 7u), 8);
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/* Advance state pointer by 1 for the next sample */
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pState = pState + 1;
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/* Decrement the samples loop counter */
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blkCnt--;
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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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tapCnt = (numTaps - 1u) >> 2u;
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/* copy data */
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while(tapCnt > 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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tapCnt--;
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}
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/* Calculate remaining number of copies */
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tapCnt = (numTaps - 1u) % 0x4u;
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/* Copy the remaining q31_t data */
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while(tapCnt > 0u)
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{
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*pStateCurnt++ = *pState++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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#else
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/* Run the below code for Cortex-M0 */
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uint32_t numTaps = S->numTaps; /* Number of taps in the filter */
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uint32_t i, blkCnt; /* Loop counters */
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q7_t *pState = S->pState; /* State pointer */
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q7_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q7_t *px, *pb; /* Temporary pointers to state and coeff */
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q31_t acc = 0; /* Accumlator */
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q7_t *pStateCurnt; /* Points to the current sample of the state */
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/* S->pState points to state array which 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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/* Initialize blkCnt with blockSize */
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blkCnt = blockSize;
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/* Perform filtering upto BlockSize - BlockSize%4 */
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while(blkCnt > 0u)
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{
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/* Copy one sample at a time into state buffer */
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*pStateCurnt++ = *pSrc++;
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/* Set accumulator to zero */
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acc = 0;
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/* Initialize state pointer of type q7 */
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px = pState;
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/* Initialize coeff pointer of type q7 */
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pb = pCoeffs;
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i = numTaps;
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while(i > 0u)
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{
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/* acc = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */
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acc += (q15_t) * px++ * *pb++;
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i--;
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}
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/* Store the 1.7 format filter output in destination buffer */
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*pDst++ = (q7_t) __SSAT((acc >> 7), 8);
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/* Advance the state pointer by 1 to process the next sample */
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pState = pState + 1;
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/* Decrement the loop counter */
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blkCnt--;
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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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/* Copy numTaps number of values */
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i = (numTaps - 1u);
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/* Copy q7_t data */
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while(i > 0u)
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{
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*pStateCurnt++ = *pState++;
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i--;
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}
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#endif /* #ifndef ARM_MATH_CM0_FAMILY */
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}
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/**
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* @} end of FIR group
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*/
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