| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_decimate_q15.c |
| * Description: Q15 FIR Decimator |
| * |
| * $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 FIR_decimate |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q15 FIR decimator. |
| @param[in] S points to an instance of the Q15 FIR decimator structure |
| @param[in] pSrc points to the block of input data |
| @param[out] pDst points to the block of output data |
| @param[in] blockSize number of input samples to process per call |
| @return none |
| |
| @par Scaling and Overflow Behavior |
| The function is implemented using a 64-bit internal accumulator. |
| Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result. |
| The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format. |
| There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved. |
| After all additions have been performed, the accumulator is truncated to 34.15 format by discarding low 15 bits. |
| Lastly, the accumulator is saturated to yield a result in 1.15 format. |
| |
| @remark |
| Refer to \ref arm_fir_decimate_fast_q15() for a faster but less precise implementation of this function. |
| */ |
| |
| #if defined (ARM_MATH_DSP) |
| |
| void arm_fir_decimate_q15( |
| const arm_fir_decimate_instance_q15 * S, |
| const q15_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q15_t *pStateCur; /* Points to the current sample of the state */ |
| q15_t *px; /* Temporary pointer for state buffer */ |
| const q15_t *pb; /* Temporary pointer for coefficient buffer */ |
| q31_t x0, x1, c0; /* Temporary variables to hold state and coefficient values */ |
| q63_t sum0; /* Accumulators */ |
| q63_t acc0, acc1; |
| q15_t *px0, *px1; |
| uint32_t blkCntN3; |
| uint32_t numTaps = S->numTaps; /* Number of taps */ |
| uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| q31_t c1; /* Temporary variables to hold state and coefficient values */ |
| #endif |
| |
| /* S->pState buffer contains previous frame (numTaps - 1) samples */ |
| /* pStateCur points to the location where the new input data should be written */ |
| pStateCur = S->pState + (numTaps - 1U); |
| |
| /* Total number of output samples to be computed */ |
| blkCnt = outBlockSize / 2; |
| blkCntN3 = outBlockSize - (2 * blkCnt); |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy 2 * decimation factor number of new input samples into the state buffer */ |
| i = S->M * 2; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| acc0 = 0; |
| acc1 = 0; |
| |
| /* Initialize state pointer for all the samples */ |
| px0 = pState; |
| px1 = pState + S->M; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] and b[numTaps-2] coefficients */ |
| c0 = read_q15x2_ia ((q15_t **) &pb); |
| |
| /* Read x[n-numTaps-1] and x[n-numTaps-2]sample */ |
| x0 = read_q15x2_ia (&px0); |
| x1 = read_q15x2_ia (&px1); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 = __SMLALD(x0, c0, acc0); |
| acc1 = __SMLALD(x1, c0, acc1); |
| |
| /* Read the b[numTaps-3] and b[numTaps-4] coefficient */ |
| c0 = read_q15x2_ia ((q15_t **) &pb); |
| |
| /* Read x[n-numTaps-2] and x[n-numTaps-3] sample */ |
| x0 = read_q15x2_ia (&px0); |
| x1 = read_q15x2_ia (&px1); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 = __SMLALD(x0, c0, acc0); |
| acc1 = __SMLALD(x1, c0, acc1); |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *pb++; |
| |
| /* Fetch state variables for acc0, acc1 */ |
| x0 = *px0++; |
| x1 = *px1++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 = __SMLALD(x0, c0, acc0); |
| acc1 = __SMLALD(x1, c0, acc1); |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M * 2; |
| |
| /* Store filter output, smlad returns the values in 2.14 format */ |
| /* so downsacle by 15 to get output in 1.15 */ |
| *pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16)); |
| *pDst++ = (q15_t) (__SSAT((acc1 >> 15), 16)); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| while (blkCntN3 > 0U) |
| { |
| /* Copy decimation factor number of new input samples into the state buffer */ |
| i = S->M; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| sum0 = 0; |
| |
| /* Initialize state pointer */ |
| px = pState; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] and b[numTaps-2] coefficients */ |
| c0 = read_q15x2_ia ((q15_t **) &pb); |
| |
| /* Read x[n-numTaps-1] and x[n-numTaps-2] sample */ |
| x0 = read_q15x2_ia (&px); |
| |
| /* Read the b[numTaps-3] and b[numTaps-4] coefficients */ |
| c1 = read_q15x2_ia ((q15_t **) &pb); |
| |
| /* Perform the multiply-accumulate */ |
| sum0 = __SMLALD(x0, c0, sum0); |
| |
| /* Read x[n-numTaps-2] and x[n-numTaps-3] sample */ |
| x0 = read_q15x2_ia (&px); |
| |
| /* Perform the multiply-accumulate */ |
| sum0 = __SMLALD(x0, c1, sum0); |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *pb++; |
| |
| /* Fetch 1 state variable */ |
| x0 = *px++; |
| |
| /* Perform the multiply-accumulate */ |
| sum0 = __SMLALD(x0, c0, sum0); |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M; |
| |
| /* Store filter output, smlad returns the values in 2.14 format */ |
| /* so downsacle by 15 to get output in 1.15 */ |
| *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16)); |
| |
| /* Decrement loop counter */ |
| blkCntN3--; |
| } |
| |
| /* 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 state buffer */ |
| pStateCur = S->pState; |
| |
| i = (numTaps - 1U) >> 2U; |
| |
| /* copy data */ |
| while (i > 0U) |
| { |
| write_q15x2_ia (&pStateCur, read_q15x2_ia (&pState)); |
| write_q15x2_ia (&pStateCur, read_q15x2_ia (&pState)); |
| |
| /* Decrement loop counter */ |
| i--; |
| } |
| |
| i = (numTaps - 1U) % 0x04U; |
| |
| /* Copy data */ |
| while (i > 0U) |
| { |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| i--; |
| } |
| |
| } |
| |
| #else /* #if defined (ARM_MATH_DSP) */ |
| |
| void arm_fir_decimate_q15( |
| const arm_fir_decimate_instance_q15 * S, |
| const q15_t * pSrc, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q15_t *pStateCur; /* Points to the current sample of the state */ |
| q15_t *px; /* Temporary pointer for state buffer */ |
| const q15_t *pb; /* Temporary pointer for coefficient buffer */ |
| q15_t x0, x1, c0; /* Temporary variables to hold state and coefficient values */ |
| q63_t sum0; /* Accumulators */ |
| q63_t acc0, acc1; |
| q15_t *px0, *px1; |
| uint32_t blkCntN3; |
| uint32_t numTaps = S->numTaps; /* Number of taps */ |
| uint32_t i, blkCnt, tapCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| |
| |
| /* S->pState buffer contains previous frame (numTaps - 1) samples */ |
| /* pStateCur points to the location where the new input data should be written */ |
| pStateCur = S->pState + (numTaps - 1U); |
| |
| /* Total number of output samples to be computed */ |
| blkCnt = outBlockSize / 2; |
| blkCntN3 = outBlockSize - (2 * blkCnt); |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy 2 * decimation factor number of new input samples into the state buffer */ |
| i = S->M * 2; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| acc0 = 0; |
| acc1 = 0; |
| |
| /* Initialize state pointer */ |
| px0 = pState; |
| px1 = pState + S->M; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the Read b[numTaps-1] coefficients */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-1] for sample 0 and for sample 1 */ |
| x0 = *px0++; |
| x1 = *px1++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-2] for sample 0 and sample 1 */ |
| x0 = *px0++; |
| x1 = *px1++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| |
| /* Read the b[numTaps-3] coefficients */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-3] for sample 0 and sample 1 */ |
| x0 = *px0++; |
| x1 = *px1++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-4] for sample 0 and sample 1 */ |
| x0 = *px0++; |
| x1 = *px1++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *pb++; |
| |
| /* Fetch 1 state variable */ |
| x0 = *px0++; |
| x1 = *px1++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += x0 * c0; |
| acc1 += x1 * c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M * 2; |
| |
| /* Store filter output, smlad returns the values in 2.14 format */ |
| /* so downsacle by 15 to get output in 1.15 */ |
| |
| *pDst++ = (q15_t) (__SSAT((acc0 >> 15), 16)); |
| *pDst++ = (q15_t) (__SSAT((acc1 >> 15), 16)); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| while (blkCntN3 > 0U) |
| { |
| /* Copy decimation factor number of new input samples into the state buffer */ |
| i = S->M; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| sum0 = 0; |
| |
| /* Initialize state pointer */ |
| px = pState; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-1] sample */ |
| x0 = *px++; |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += x0 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-2] sample */ |
| x0 = *px++; |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += x0 * c0; |
| |
| /* Read the b[numTaps-3] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-3] sample */ |
| x0 = *px++; |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += x0 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-4] sample */ |
| x0 = *px++; |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += x0 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *pb++; |
| |
| /* Fetch 1 state variable */ |
| x0 = *px++; |
| |
| /* Perform the multiply-accumulate */ |
| sum0 += x0 * c0; |
| |
| /* Decrement the loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M; |
| |
| /* Store filter output, smlad returns the values in 2.14 format */ |
| /* so downsacle by 15 to get output in 1.15 */ |
| *pDst++ = (q15_t) (__SSAT((sum0 >> 15), 16)); |
| |
| /* Decrement loop counter */ |
| blkCntN3--; |
| } |
| |
| /* 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 state buffer */ |
| pStateCur = S->pState; |
| |
| i = (numTaps - 1U) >> 2U; |
| |
| /* copy data */ |
| while (i > 0U) |
| { |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| i--; |
| } |
| |
| i = (numTaps - 1U) % 0x04U; |
| |
| /* copy data */ |
| while (i > 0U) |
| { |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| i--; |
| } |
| } |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| /** |
| @} end of FIR_decimate group |
| */ |