| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_lms_q31.c |
| * Description: Processing function for the Q31 LMS filter |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 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 Q31 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, |
| const q31_t * pSrc, |
| q31_t * pRef, |
| q31_t * pOut, |
| q31_t * pErr, |
| uint32_t blockSize) |
| { |
| q31_t *pState = S->pState; /* State pointer */ |
| q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q31_t *pStateCurnt; /* Points to the current sample of the state */ |
| q31_t *px, *pb; /* Temporary pointers for state and coefficient buffers */ |
| q31_t mu = S->mu; /* Adaptive factor */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| 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)]); |
| |
| /* initialise loop count */ |
| blkCnt = blockSize; |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy the new input sample into the state buffer */ |
| *pStateCurnt++ = *pSrc++; |
| |
| /* Initialize pState pointer */ |
| px = pState; |
| |
| /* Initialize coefficient pointer */ |
| pb = pCoeffs; |
| |
| /* Set the accumulator to zero */ |
| acc = 0; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time. */ |
| tapCnt = numTaps >> 2U; |
| |
| 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 loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of samples */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| 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++ = e; |
| |
| /* Compute alpha i.e. intermediate constant for taps update */ |
| alpha = (q31_t) (((q63_t) e * mu) >> 31); |
| |
| /* Initialize pState pointer */ |
| /* Advance state pointer by 1 for the next sample */ |
| px = pState++; |
| |
| /* Initialize coefficient pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time. */ |
| tapCnt = numTaps >> 2U; |
| |
| /* Update filter coefficients */ |
| while (tapCnt > 0U) |
| { |
| /* Perform the multiply-accumulate */ |
| |
| /* 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 loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of samples */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| 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 loop counter */ |
| tapCnt--; |
| } |
| |
| /* Decrement 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 data */ |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time. */ |
| tapCnt = (numTaps - 1U) >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = (numTaps - 1U) % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of samples */ |
| tapCnt = (numTaps - 1U); |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| *pStateCurnt++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| } |
| |
| /** |
| @} end of LMS group |
| */ |