/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_lms_q31.c
* Description: Processing function for the Q31 LMS filter
*
* $Date: 27. January 2017
* $Revision: V.1.5.1
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @addtogroup LMS
* @{
*/
/**
* @brief Processing function for Q31 LMS filter.
* @param[in] *S points to an instance of the Q15 LMS filter structure.
* @param[in] *pSrc points to the block of input data.
* @param[in] *pRef points to the block of reference data.
* @param[out] *pOut points to the block of output data.
* @param[out] *pErr points to the block of error data.
* @param[in] blockSize number of samples to process.
* @return none.
*
* \par Scaling and Overflow Behavior:
* The function is implemented using an internal 64-bit accumulator.
* The accumulator has a 2.62 format and maintains full precision of the intermediate
* multiplication results but provides only a single guard bit.
* Thus, if the accumulator result overflows it wraps around rather than clips.
* In order to avoid overflows completely the input signal must be scaled down by
* log2(numTaps) bits.
* The reference signal should not be scaled down.
* After all multiply-accumulates are performed, the 2.62 accumulator is shifted
* and saturated to 1.31 format to yield the final result.
* The output signal and error signal are in 1.31 format.
*
* \par
* In this filter, filter coefficients are updated for each sample and the updation of filter cofficients are saturted.
*/
void arm_lms_q31(
const arm_lms_instance_q31 * S,
q31_t * pSrc,
q31_t * pRef,
q31_t * pOut,
q31_t * pErr,
uint32_t blockSize)
{
q31_t *pState = S->pState; /* State pointer */
uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
q31_t *pStateCurnt; /* Points to the current sample of the state */
q31_t mu = S->mu; /* Adaptive factor */
q31_t *px; /* Temporary pointer for state */
q31_t *pb; /* Temporary pointer for coefficient buffer */
uint32_t tapCnt, blkCnt; /* Loop counters */
q63_t acc; /* Accumulator */
q31_t e = 0; /* error of data sample */
q31_t alpha; /* Intermediate constant for taps update */
q31_t coef; /* Temporary variable for coef */
q31_t acc_l, acc_h; /* temporary input */
uint32_t uShift = ((uint32_t) S->postShift + 1U);
uint32_t lShift = 32U - uShift; /* Shift to be applied to the output */
/* S->pState points to buffer which contains previous frame (numTaps - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = &(S->pState[(numTaps - 1U)]);
/* Initializing blkCnt with blockSize */
blkCnt = blockSize;
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
while (blkCnt > 0U)
{
/* Copy the new input sample into the state buffer */
*pStateCurnt++ = *pSrc++;
/* Initialize state pointer */
px = pState;
/* Initialize coefficient pointer */
pb = pCoeffs;
/* Set the accumulator to zero */
acc = 0;
/* Loop unrolling. Process 4 taps at a time. */
tapCnt = numTaps >> 2;
while (tapCnt > 0U)
{
/* Perform the multiply-accumulate */
/* acc += b[N] * x[n-N] */
acc += ((q63_t) (*px++)) * (*pb++);
/* acc += b[N-1] * x[n-N-1] */
acc += ((q63_t) (*px++)) * (*pb++);
/* acc += b[N-2] * x[n-N-2] */
acc += ((q63_t) (*px++)) * (*pb++);
/* acc += b[N-3] * x[n-N-3] */
acc += ((q63_t) (*px++)) * (*pb++);
/* Decrement the loop counter */
tapCnt--;
}
/* If the filter length is not a multiple of 4, compute the remaining filter taps */
tapCnt = numTaps % 0x4U;
while (tapCnt > 0U)
{
/* Perform the multiply-accumulate */
acc += ((q63_t) (*px++)) * (*pb++);
/* Decrement the loop counter */
tapCnt--;
}
/* Converting the result to 1.31 format */
/* Calc lower part of acc */
acc_l = acc & 0xffffffff;
/* Calc upper part of acc */
acc_h = (acc >> 32) & 0xffffffff;
acc = (uint32_t) acc_l >> lShift | acc_h << uShift;
/* Store the result from accumulator into the destination buffer. */
*pOut++ = (q31_t) acc;
/* Compute and store error */
e = *pRef++ - (q31_t) acc;
*pErr++ = (q31_t) e;
/* Compute alpha i.e. intermediate constant for taps update */
alpha = (q31_t) (((q63_t) e * mu) >> 31);
/* Initialize state pointer */
/* Advance state pointer by 1 for the next sample */
px = pState++;
/* Initialize coefficient pointer */
pb = pCoeffs;
/* Loop unrolling. Process 4 taps at a time. */
tapCnt = numTaps >> 2;
/* Update filter coefficients */
while (tapCnt > 0U)
{
/* coef is in 2.30 format */
coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
/* get coef in 1.31 format by left shifting */
*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
/* update coefficient buffer to next coefficient */
pb++;
coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
pb++;
coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
pb++;
coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
pb++;
/* Decrement the loop counter */
tapCnt--;
}
/* If the filter length is not a multiple of 4, compute the remaining filter taps */
tapCnt = numTaps % 0x4U;
while (tapCnt > 0U)
{
/* Perform the multiply-accumulate */
coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
pb++;
/* Decrement the loop counter */
tapCnt--;
}
/* Decrement the loop counter */
blkCnt--;
}
/* Processing is complete. Now copy the last numTaps - 1 samples to the
satrt of the state buffer. This prepares the state buffer for the
next function call. */
/* Points to the start of the pState buffer */
pStateCurnt = S->pState;
/* Loop unrolling for (numTaps - 1U) samples copy */
tapCnt = (numTaps - 1U) >> 2U;
/* copy data */
while (tapCnt > 0U)
{
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
/* Calculate remaining number of copies */
tapCnt = (numTaps - 1U) % 0x4U;
/* Copy the remaining q31_t data */
while (tapCnt > 0U)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
#else
/* Run the below code for Cortex-M0 */
while (blkCnt > 0U)
{
/* Copy the new input sample into the state buffer */
*pStateCurnt++ = *pSrc++;
/* Initialize pState pointer */
px = pState;
/* Initialize pCoeffs pointer */
pb = pCoeffs;
/* Set the accumulator to zero */
acc = 0;
/* Loop over numTaps number of values */
tapCnt = numTaps;
while (tapCnt > 0U)
{
/* Perform the multiply-accumulate */
acc += ((q63_t) (*px++)) * (*pb++);
/* Decrement the loop counter */
tapCnt--;
}
/* Converting the result to 1.31 format */
/* Store the result from accumulator into the destination buffer. */
/* Calc lower part of acc */
acc_l = acc & 0xffffffff;
/* Calc upper part of acc */
acc_h = (acc >> 32) & 0xffffffff;
acc = (uint32_t) acc_l >> lShift | acc_h << uShift;
*pOut++ = (q31_t) acc;
/* Compute and store error */
e = *pRef++ - (q31_t) acc;
*pErr++ = (q31_t) e;
/* Weighting factor for the LMS version */
alpha = (q31_t) (((q63_t) e * mu) >> 31);
/* Initialize pState pointer */
/* Advance state pointer by 1 for the next sample */
px = pState++;
/* Initialize pCoeffs pointer */
pb = pCoeffs;
/* Loop over numTaps number of values */
tapCnt = numTaps;
while (tapCnt > 0U)
{
/* Perform the multiply-accumulate */
coef = (q31_t) (((q63_t) alpha * (*px++)) >> (32));
*pb = clip_q63_to_q31((q63_t) * pb + (coef << 1U));
pb++;
/* Decrement the loop counter */
tapCnt--;
}
/* Decrement the loop counter */
blkCnt--;
}
/* Processing is complete. Now copy the last numTaps - 1 samples to the
start of the state buffer. This prepares the state buffer for the
next function call. */
/* Points to the start of the pState buffer */
pStateCurnt = S->pState;
/* Copy (numTaps - 1U) samples */
tapCnt = (numTaps - 1U);
/* Copy the data */
while (tapCnt > 0U)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
#endif /* #if defined (ARM_MATH_DSP) */
}
/**
* @} end of LMS group
*/