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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_lms_q31.c
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*
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* Description: Processing function for the Q31 LMS filter.
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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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* @ingroup groupFilters
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*/
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/**
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* @addtogroup LMS
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* @{
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*/
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/**
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* @brief Processing function for Q31 LMS filter.
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* @param[in] *S points to an instance of the Q15 LMS filter structure.
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* @param[in] *pSrc points to the block of input data.
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* @param[in] *pRef points to the block of reference data.
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* @param[out] *pOut points to the block of output data.
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* @param[out] *pErr points to the block of error 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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* \par Scaling and Overflow Behavior:
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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
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* multiplication results but provides only a single guard bit.
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* Thus, if the accumulator result overflows it wraps around rather than clips.
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* In order to avoid overflows completely the input signal must be scaled down by
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* log2(numTaps) bits.
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* The reference signal should not be scaled down.
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* After all multiply-accumulates are performed, the 2.62 accumulator is shifted
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* and saturated to 1.31 format to yield the final result.
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* The output signal and error signal are in 1.31 format.
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*
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* \par
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* In this filter, filter coefficients are updated for each sample and the updation of filter cofficients are saturted.
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*/
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void arm_lms_q31(
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const arm_lms_instance_q31 * S,
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q31_t * pSrc,
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q31_t * pRef,
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q31_t * pOut,
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q31_t * pErr,
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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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uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
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q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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q31_t *pStateCurnt; /* Points to the current sample of the state */
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q31_t mu = S->mu; /* Adaptive factor */
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q31_t *px; /* Temporary pointer for state */
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q31_t *pb; /* Temporary pointer for coefficient buffer */
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uint32_t tapCnt, blkCnt; /* Loop counters */
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q63_t acc; /* Accumulator */
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q31_t e = 0; /* error of data sample */
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q31_t alpha; /* Intermediate constant for taps update */
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uint8_t shift = (uint8_t) (32u - (S->postShift + 1u)); /* Shift to be applied to the output */
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q31_t coef; /* Temporary variable for coef */
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/* S->pState points to buffer 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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/* Initializing blkCnt with blockSize */
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blkCnt = blockSize;
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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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while(blkCnt > 0u)
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{
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/* Copy the new input sample into the state buffer */
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*pStateCurnt++ = *pSrc++;
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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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/* Set the accumulator to zero */
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acc = 0;
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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while(tapCnt > 0u)
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{
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/* Perform the multiply-accumulate */
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/* acc += b[N] * x[n-N] */
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acc += ((q63_t) (*px++)) * (*pb++);
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/* acc += b[N-1] * x[n-N-1] */
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acc += ((q63_t) (*px++)) * (*pb++);
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/* acc += b[N-2] * x[n-N-2] */
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acc += ((q63_t) (*px++)) * (*pb++);
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/* acc += b[N-3] * x[n-N-3] */
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acc += ((q63_t) (*px++)) * (*pb++);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the filter length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = numTaps % 0x4u;
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while(tapCnt > 0u)
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{
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/* Perform the multiply-accumulate */
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acc += ((q63_t) (*px++)) * (*pb++);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Converting the result to 1.31 format */
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/* Store the result from accumulator into the destination buffer. */
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acc = (q31_t) (acc >> shift);
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*pOut++ = (q31_t) acc;
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/* Compute and store error */
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e = *pRef++ - (q31_t) acc;
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*pErr++ = (q31_t) e;
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/* Compute alpha i.e. intermediate constant for taps update */
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alpha = (q31_t) (((q63_t) e * mu) >> 31);
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/* Initialize state pointer */
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/* Advance state pointer by 1 for the next sample */
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px = pState++;
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/* Initialize coefficient pointer */
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pb = pCoeffs;
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/* Loop unrolling. Process 4 taps at a time. */
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tapCnt = numTaps >> 2;
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/* Update filter coefficients */
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while(tapCnt > 0u)
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{
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/* coef is in 2.30 format */
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coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
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/* get coef in 1.31 format by left shifting */
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*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1u));
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/* update coefficient buffer to next coefficient */
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pb++;
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coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
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*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1u));
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pb++;
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coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
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*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1u));
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pb++;
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coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
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*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1u));
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pb++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* If the filter length is not a multiple of 4, compute the remaining filter taps */
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tapCnt = numTaps % 0x4u;
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while(tapCnt > 0u)
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{
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/* Perform the multiply-accumulate */
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coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
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*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1u));
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pb++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Processing is complete. Now copy the last numTaps - 1 samples to the
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satrt of the state buffer. This prepares the state buffer for the
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next function call. */
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/* Points to the start of the pState buffer */
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pStateCurnt = S->pState;
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/* Loop unrolling for (numTaps - 1u) samples copy */
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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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while(blkCnt > 0u)
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{
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/* Copy the new input sample into the state buffer */
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*pStateCurnt++ = *pSrc++;
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/* Initialize pState pointer */
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px = pState;
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/* Initialize pCoeffs pointer */
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pb = pCoeffs;
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/* Set the accumulator to zero */
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acc = 0;
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/* Loop over numTaps number of values */
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tapCnt = numTaps;
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while(tapCnt > 0u)
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{
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/* Perform the multiply-accumulate */
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acc += ((q63_t) (*px++)) * (*pb++);
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Converting the result to 1.31 format */
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/* Store the result from accumulator into the destination buffer. */
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acc = (q31_t) (acc >> shift);
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*pOut++ = (q31_t) acc;
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/* Compute and store error */
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e = *pRef++ - (q31_t) acc;
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*pErr++ = (q31_t) e;
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/* Weighting factor for the LMS version */
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alpha = (q31_t) (((q63_t) e * mu) >> 31);
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/* Initialize pState pointer */
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/* Advance state pointer by 1 for the next sample */
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px = pState++;
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/* Initialize pCoeffs pointer */
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pb = pCoeffs;
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/* Loop over numTaps number of values */
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tapCnt = numTaps;
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while(tapCnt > 0u)
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{
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/* Perform the multiply-accumulate */
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coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
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*pb += (coef << 1u);
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pb++;
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/* Decrement the loop counter */
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tapCnt--;
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}
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* Processing is complete. Now copy the last numTaps - 1 samples to the
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start of the state buffer. This prepares the state buffer for the
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next function call. */
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/* Points to the start of the pState buffer */
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pStateCurnt = S->pState;
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/* Copy (numTaps - 1u) samples */
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tapCnt = (numTaps - 1u);
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/* Copy the 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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#endif /* #ifndef ARM_MATH_CM0 */
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}
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/**
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* @} end of LMS group
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*/
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