| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_sparse_q15.c |
| * Description: Q15 sparse FIR filter processing function |
| * |
| * $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_Sparse |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q15 sparse FIR filter. |
| @param[in] S points to an instance of the Q15 sparse FIR structure |
| @param[in] pSrc points to the block of input data |
| @param[out] pDst points to the block of output data |
| @param[in] pScratchIn points to a temporary buffer of size blockSize |
| @param[in] pScratchOut points to a temporary buffer of size blockSize |
| @param[in] blockSize number of input samples to process per call |
| @return none |
| |
| @par Scaling and Overflow Behavior |
| The function is implemented using an internal 32-bit accumulator. |
| The 1.15 x 1.15 multiplications yield a 2.30 result and these are added to a 2.30 accumulator. |
| Thus the full precision of the multiplications is maintained but there is only a single guard bit in the accumulator. |
| If the accumulator result overflows it will wrap around rather than saturate. |
| After all multiply-accumulates are performed, the 2.30 accumulator is truncated to 2.15 format and then saturated to 1.15 format. |
| In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits. |
| */ |
| |
| void arm_fir_sparse_q15( |
| arm_fir_sparse_instance_q15 * S, |
| const q15_t * pSrc, |
| q15_t * pDst, |
| q15_t * pScratchIn, |
| q31_t * pScratchOut, |
| uint32_t blockSize) |
| { |
| q15_t *pState = S->pState; /* State pointer */ |
| const q15_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q15_t *px; /* Temporary pointers for scratch buffer */ |
| q15_t *py = pState; /* Temporary pointers for state buffer */ |
| q15_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */ |
| q15_t *pOut = pDst; /* Working pointer for output */ |
| int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */ |
| uint32_t delaySize = S->maxDelay + blockSize; /* state length */ |
| uint16_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| int32_t readIndex; /* Read index of the state buffer */ |
| uint32_t tapCnt, blkCnt; /* loop counters */ |
| q31_t *pScr2 = pScratchOut; /* Working pointer for scratch buffer of output values */ |
| q15_t coeff = *pCoeffs++; /* Read the first coefficient value */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| q31_t in1, in2; /* Temporary variables */ |
| #endif |
| |
| /* BlockSize of Input samples are copied into the state buffer */ |
| /* StateIndex points to the starting position to write in the state buffer */ |
| arm_circularWrite_q15(py, (int32_t) delaySize, &S->stateIndex, 1,pSrc, 1, blockSize); |
| |
| /* Loop over the number of taps. */ |
| tapCnt = numTaps; |
| |
| /* Read Index, from where the state buffer should be read, is calculated. */ |
| readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; |
| |
| /* Wraparound of readIndex */ |
| if (readIndex < 0) |
| { |
| readIndex += (int32_t) delaySize; |
| } |
| |
| /* Working pointer for state buffer is updated */ |
| py = pState; |
| |
| /* blockSize samples are read from the state buffer */ |
| arm_circularRead_q15(py, (int32_t) delaySize, &readIndex, 1, |
| pb, pb, (int32_t) blockSize, 1, blockSize); |
| |
| /* Working pointer for the scratch buffer of state values */ |
| px = pb; |
| |
| /* Working pointer for scratch buffer of output values */ |
| pScratchOut = pScr2; |
| |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform multiplication and store in the scratch buffer */ |
| *pScratchOut++ = ((q31_t) *px++ * coeff); |
| *pScratchOut++ = ((q31_t) *px++ * coeff); |
| *pScratchOut++ = ((q31_t) *px++ * coeff); |
| *pScratchOut++ = ((q31_t) *px++ * coeff); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiplication and store in the scratch buffer */ |
| *pScratchOut++ = ((q31_t) *px++ * coeff); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Load the coefficient value and |
| * increment the coefficient buffer for the next set of state values */ |
| coeff = *pCoeffs++; |
| |
| /* Read Index, from where the state buffer should be read, is calculated. */ |
| readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; |
| |
| /* Wraparound of readIndex */ |
| if (readIndex < 0) |
| { |
| readIndex += (int32_t) delaySize; |
| } |
| |
| /* Loop over the number of taps. */ |
| tapCnt = (uint32_t) numTaps - 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Working pointer for state buffer is updated */ |
| py = pState; |
| |
| /* blockSize samples are read from the state buffer */ |
| arm_circularRead_q15(py, (int32_t) delaySize, &readIndex, 1, |
| pb, pb, (int32_t) blockSize, 1, blockSize); |
| |
| /* Working pointer for the scratch buffer of state values */ |
| px = pb; |
| |
| /* Working pointer for scratch buffer of output values */ |
| pScratchOut = pScr2; |
| |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Load the coefficient value and |
| * increment the coefficient buffer for the next set of state values */ |
| coeff = *pCoeffs++; |
| |
| /* Read Index, from where the state buffer should be read, is calculated. */ |
| readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++; |
| |
| /* Wraparound of readIndex */ |
| if (readIndex < 0) |
| { |
| readIndex += (int32_t) delaySize; |
| } |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Compute last tap without the final read of pTapDelay */ |
| |
| /* Working pointer for state buffer is updated */ |
| py = pState; |
| |
| /* blockSize samples are read from the state buffer */ |
| arm_circularRead_q15(py, (int32_t) delaySize, &readIndex, 1, |
| pb, pb, (int32_t) blockSize, 1, blockSize); |
| |
| /* Working pointer for the scratch buffer of state values */ |
| px = pb; |
| |
| /* Working pointer for scratch buffer of output values */ |
| pScratchOut = pScr2; |
| |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Perform Multiply-Accumulate */ |
| *pScratchOut++ += (q31_t) *px++ * coeff; |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* All the output values are in pScratchOut buffer. |
| Convert them into 1.15 format, saturate and store in the destination buffer. */ |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 outputs at a time. */ |
| blkCnt = blockSize >> 2U; |
| |
| while (blkCnt > 0U) |
| { |
| in1 = *pScr2++; |
| in2 = *pScr2++; |
| |
| #ifndef ARM_MATH_BIG_ENDIAN |
| write_q15x2_ia (&pOut, __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16), 16)); |
| #else |
| write_q15x2_ia (&pOut, __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16), 16)); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| |
| in1 = *pScr2++; |
| in2 = *pScr2++; |
| |
| #ifndef ARM_MATH_BIG_ENDIAN |
| write_q15x2_ia (&pOut, __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16), 16)); |
| #else |
| write_q15x2_ia (&pOut, __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16), 16)); |
| #endif /* #ifndef ARM_MATH_BIG_ENDIAN */ |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining outputs */ |
| blkCnt = blockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| *pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| } |
| |
| /** |
| @} end of FIR_Sparse group |
| */ |
