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/* ----------------------------------------------------------------------
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* Copyright (C) 2010 ARM Limited. All rights reserved.
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*
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* $Date: 15. July 2011
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* $Revision: V1.0.10
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*
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* Project: CMSIS DSP Library
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* Title: arm_fir_sparse_q31.c
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*
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* Description: Q31 sparse 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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* Version 1.0.10 2011/7/15
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* Big Endian support added and Merged M0 and M3/M4 Source code.
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*
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* Version 1.0.3 2010/11/29
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* Re-organized the CMSIS folders and updated documentation.
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*
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* Version 1.0.2 2010/11/11
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* Documentation updated.
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*
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* Version 1.0.1 2010/10/05
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* Production release and review comments incorporated.
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*
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* Version 1.0.0 2010/09/20
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* Production release and review comments incorporated
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*
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* Version 0.0.7 2010/06/10
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* Misra-C changes done
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* ------------------------------------------------------------------- */
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#include "arm_math.h"
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/**
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* @addtogroup FIR_Sparse
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* @{
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*/
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/**
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* @brief Processing function for the Q31 sparse FIR filter.
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* @param[in] *S points to an instance of the Q31 sparse FIR structure.
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* @param[in] *pSrc points to the block of input data.
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* @param[out] *pDst points to the block of output data
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* @param[in] *pScratchIn points to a temporary buffer of size blockSize.
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* @param[in] blockSize number of input samples to process per call.
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* @return none.
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*
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* <b>Scaling and Overflow Behavior:</b>
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* \par
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* The function is implemented using an internal 32-bit accumulator.
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* The 1.31 x 1.31 multiplications are truncated to 2.30 format.
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* This leads to loss of precision on the intermediate multiplications and provides only a single guard bit.
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* If the accumulator result overflows, it wraps around rather than saturate.
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* In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits.
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*/
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void arm_fir_sparse_q31(
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arm_fir_sparse_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pDst,
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q31_t * pScratchIn,
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uint32_t blockSize)
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{
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q31_t *pState = S->pState; /* State pointer */
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q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q31_t *px; /* Scratch buffer pointer */
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q31_t *py = pState; /* Temporary pointers for state buffer */
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q31_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */
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q31_t *pOut; /* Destination pointer */
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q63_t out; /* Temporary output variable */
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int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */
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uint32_t delaySize = S->maxDelay + blockSize; /* state length */
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uint16_t numTaps = S->numTaps; /* Filter order */
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int32_t readIndex; /* Read index of the state buffer */
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uint32_t tapCnt, blkCnt; /* loop counters */
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q31_t coeff = *pCoeffs++; /* Read the first coefficient value */
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q31_t in;
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/* BlockSize of Input samples are copied into the state buffer */
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/* StateIndex points to the starting position to write in the state buffer */
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arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1,
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(int32_t *) pSrc, 1, blockSize);
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if(readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
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(int32_t *) pb, (int32_t *) pb, blockSize, 1,
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blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pOut = pDst;
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#ifndef ARM_MATH_CM0
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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/* Loop over the blockSize. Unroll by a factor of 4.
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* Compute 4 Multiplications at a time. */
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blkCnt = blockSize >> 2;
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while(blkCnt > 0u)
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{
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/* Perform Multiplications and store in the destination buffer */
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*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
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*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
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*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
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*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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* compute the remaining samples */
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blkCnt = blockSize % 0x4u;
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while(blkCnt > 0u)
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{
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/* Perform Multiplications and store in the destination buffer */
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*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if(readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Loop over the number of taps. */
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tapCnt = (uint32_t) numTaps - 1u;
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while(tapCnt > 0u)
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{
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
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(int32_t *) pb, (int32_t *) pb, blockSize, 1,
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blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pOut = pDst;
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/* Loop over the blockSize. Unroll by a factor of 4.
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* Compute 4 MACS at a time. */
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blkCnt = blockSize >> 2;
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while(blkCnt > 0u)
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{
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out = *pOut;
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out += ((q63_t) * px++ * coeff) >> 32;
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*pOut++ = (q31_t) (out);
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out = *pOut;
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out += ((q63_t) * px++ * coeff) >> 32;
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*pOut++ = (q31_t) (out);
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out = *pOut;
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out += ((q63_t) * px++ * coeff) >> 32;
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*pOut++ = (q31_t) (out);
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out = *pOut;
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out += ((q63_t) * px++ * coeff) >> 32;
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*pOut++ = (q31_t) (out);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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* compute the remaining samples */
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blkCnt = blockSize % 0x4u;
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while(blkCnt > 0u)
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{
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/* Perform Multiply-Accumulate */
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out = *pOut;
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out += ((q63_t) * px++ * coeff) >> 32;
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*pOut++ = (q31_t) (out);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if(readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Decrement the tap loop counter */
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tapCnt--;
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}
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/* Working output pointer is updated */
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pOut = pDst;
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/* Output is converted into 1.31 format. */
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/* Loop over the blockSize. Unroll by a factor of 4.
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* process 4 output samples at a time. */
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blkCnt = blockSize >> 2;
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while(blkCnt > 0u)
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{
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in = *pOut << 1;
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*pOut++ = in;
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in = *pOut << 1;
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*pOut++ = in;
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in = *pOut << 1;
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*pOut++ = in;
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in = *pOut << 1;
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*pOut++ = in;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4,
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* process the remaining output samples */
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blkCnt = blockSize % 0x4u;
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while(blkCnt > 0u)
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{
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in = *pOut << 1;
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*pOut++ = in;
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/* Decrement the loop counter */
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blkCnt--;
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}
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#else
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/* Run the below code for Cortex-M0 */
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blkCnt = blockSize;
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while(blkCnt > 0u)
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{
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/* Perform Multiplications and store in the destination buffer */
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*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if(readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Loop over the number of taps. */
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tapCnt = (uint32_t) numTaps - 1u;
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while(tapCnt > 0u)
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{
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/* Working pointer for state buffer is updated */
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py = pState;
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/* blockSize samples are read from the state buffer */
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arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
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(int32_t *) pb, (int32_t *) pb, blockSize, 1,
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blockSize);
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/* Working pointer for the scratch buffer of state values */
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px = pb;
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/* Working pointer for scratch buffer of output values */
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pOut = pDst;
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blkCnt = blockSize;
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while(blkCnt > 0u)
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{
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/* Perform Multiply-Accumulate */
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out = *pOut;
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out += ((q63_t) * px++ * coeff) >> 32;
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*pOut++ = (q31_t) (out);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Load the coefficient value and
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* increment the coefficient buffer for the next set of state values */
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coeff = *pCoeffs++;
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/* Read Index, from where the state buffer should be read, is calculated. */
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readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
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/* Wraparound of readIndex */
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if(readIndex < 0)
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{
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readIndex += (int32_t) delaySize;
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}
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/* Decrement the tap loop counter */
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tapCnt--;
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}
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/* Working output pointer is updated */
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pOut = pDst;
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/* Output is converted into 1.31 format. */
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blkCnt = blockSize;
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while(blkCnt > 0u)
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{
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in = *pOut << 1;
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*pOut++ = in;
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/* Decrement the loop counter */
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blkCnt--;
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}
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#endif /* #ifndef ARM_MATH_CM0 */
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}
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/**
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* @} end of FIR_Sparse group
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*/
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