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Diffstat (limited to 'DSP_Lib/Source/FilteringFunctions/arm_fir_fast_q31.c')
-rw-r--r-- | DSP_Lib/Source/FilteringFunctions/arm_fir_fast_q31.c | 305 |
1 files changed, 305 insertions, 0 deletions
diff --git a/DSP_Lib/Source/FilteringFunctions/arm_fir_fast_q31.c b/DSP_Lib/Source/FilteringFunctions/arm_fir_fast_q31.c new file mode 100644 index 0000000..13073c4 --- /dev/null +++ b/DSP_Lib/Source/FilteringFunctions/arm_fir_fast_q31.c @@ -0,0 +1,305 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 19. March 2015 +* $Revision: V.1.4.5 +* +* Project: CMSIS DSP Library +* Title: arm_fir_fast_q31.c +* +* Description: Processing function for the Q31 Fast FIR filter. +* +* Target Processor: Cortex-M4/Cortex-M3 +* +* Redistribution and use in source and binary forms, with or without +* modification, are permitted provided that the following conditions +* are met: +* - Redistributions of source code must retain the above copyright +* notice, this list of conditions and the following disclaimer. +* - Redistributions in binary form must reproduce the above copyright +* notice, this list of conditions and the following disclaimer in +* the documentation and/or other materials provided with the +* distribution. +* - Neither the name of ARM LIMITED nor the names of its contributors +* may be used to endorse or promote products derived from this +* software without specific prior written permission. +* +* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS +* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE +* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, +* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, +* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER +* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN +* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +* POSSIBILITY OF SUCH DAMAGE. +* -------------------------------------------------------------------- */ + +#include "arm_math.h" + +/** + * @ingroup groupFilters + */ + +/** + * @addtogroup FIR + * @{ + */ + +/** + * @param[in] *S points to an instance of the Q31 structure. + * @param[in] *pSrc points to the block of input data. + * @param[out] *pDst points to the block output data. + * @param[in] blockSize number of samples to process per call. + * @return none. + * + * <b>Scaling and Overflow Behavior:</b> + * + * \par + * This function is optimized for speed at the expense of fixed-point precision and overflow protection. + * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format. + * These intermediate results are added to a 2.30 accumulator. + * Finally, the accumulator is saturated and converted to a 1.31 result. + * The fast version has the same overflow behavior as the standard version and provides less precision since it discards the low 32 bits of each multiplication result. + * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits. + * + * \par + * Refer to the function <code>arm_fir_q31()</code> for a slower implementation of this function which uses a 64-bit accumulator to provide higher precision. Both the slow and the fast versions use the same instance structure. + * Use the function <code>arm_fir_init_q31()</code> to initialize the filter structure. + */ + +IAR_ONLY_LOW_OPTIMIZATION_ENTER +void arm_fir_fast_q31( + const arm_fir_instance_q31 * S, + q31_t * pSrc, + q31_t * pDst, + 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 x0, x1, x2, x3; /* Temporary variables to hold state */ + q31_t c0; /* Temporary variable to hold coefficient value */ + q31_t *px; /* Temporary pointer for state */ + q31_t *pb; /* Temporary pointer for coefficient buffer */ + q31_t acc0, acc1, acc2, acc3; /* Accumulators */ + uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ + uint32_t i, tapCnt, blkCnt; /* Loop counters */ + + /* 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)]); + + /* Apply loop unrolling and compute 4 output values simultaneously. + * The variables acc0 ... acc3 hold output values that are being computed: + * + * acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] + * acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1] + * acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2] + * acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3] + */ + blkCnt = blockSize >> 2; + + /* First part of the processing with loop unrolling. Compute 4 outputs at a time. + ** a second loop below computes the remaining 1 to 3 samples. */ + while(blkCnt > 0u) + { + /* Copy four new input samples into the state buffer */ + *pStateCurnt++ = *pSrc++; + *pStateCurnt++ = *pSrc++; + *pStateCurnt++ = *pSrc++; + *pStateCurnt++ = *pSrc++; + + /* Set all accumulators to zero */ + acc0 = 0; + acc1 = 0; + acc2 = 0; + acc3 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize coefficient pointer */ + pb = pCoeffs; + + /* Read the first three samples from the state buffer: + * x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */ + x0 = *(px++); + x1 = *(px++); + x2 = *(px++); + + /* Loop unrolling. Process 4 taps at a time. */ + tapCnt = numTaps >> 2; + i = tapCnt; + + while(i > 0u) + { + /* Read the b[numTaps] coefficient */ + c0 = *pb; + + /* Read x[n-numTaps-3] sample */ + x3 = *px; + + /* acc0 += b[numTaps] * x[n-numTaps] */ + multAcc_32x32_keep32_R(acc0, x0, c0); + + /* acc1 += b[numTaps] * x[n-numTaps-1] */ + multAcc_32x32_keep32_R(acc1, x1, c0); + + /* acc2 += b[numTaps] * x[n-numTaps-2] */ + multAcc_32x32_keep32_R(acc2, x2, c0); + + /* acc3 += b[numTaps] * x[n-numTaps-3] */ + multAcc_32x32_keep32_R(acc3, x3, c0); + + /* Read the b[numTaps-1] coefficient */ + c0 = *(pb + 1u); + + /* Read x[n-numTaps-4] sample */ + x0 = *(px + 1u); + + /* Perform the multiply-accumulates */ + multAcc_32x32_keep32_R(acc0, x1, c0); + multAcc_32x32_keep32_R(acc1, x2, c0); + multAcc_32x32_keep32_R(acc2, x3, c0); + multAcc_32x32_keep32_R(acc3, x0, c0); + + /* Read the b[numTaps-2] coefficient */ + c0 = *(pb + 2u); + + /* Read x[n-numTaps-5] sample */ + x1 = *(px + 2u); + + /* Perform the multiply-accumulates */ + multAcc_32x32_keep32_R(acc0, x2, c0); + multAcc_32x32_keep32_R(acc1, x3, c0); + multAcc_32x32_keep32_R(acc2, x0, c0); + multAcc_32x32_keep32_R(acc3, x1, c0); + + /* Read the b[numTaps-3] coefficients */ + c0 = *(pb + 3u); + + /* Read x[n-numTaps-6] sample */ + x2 = *(px + 3u); + + /* Perform the multiply-accumulates */ + multAcc_32x32_keep32_R(acc0, x3, c0); + multAcc_32x32_keep32_R(acc1, x0, c0); + multAcc_32x32_keep32_R(acc2, x1, c0); + multAcc_32x32_keep32_R(acc3, x2, c0); + + /* update coefficient pointer */ + pb += 4u; + px += 4u; + + /* Decrement the loop counter */ + i--; + } + + /* If the filter length is not a multiple of 4, compute the remaining filter taps */ + + i = numTaps - (tapCnt * 4u); + while(i > 0u) + { + /* Read coefficients */ + c0 = *(pb++); + + /* Fetch 1 state variable */ + x3 = *(px++); + + /* Perform the multiply-accumulates */ + multAcc_32x32_keep32_R(acc0, x0, c0); + multAcc_32x32_keep32_R(acc1, x1, c0); + multAcc_32x32_keep32_R(acc2, x2, c0); + multAcc_32x32_keep32_R(acc3, x3, c0); + + /* Reuse the present sample states for next sample */ + x0 = x1; + x1 = x2; + x2 = x3; + + /* Decrement the loop counter */ + i--; + } + + /* Advance the state pointer by 4 to process the next group of 4 samples */ + pState = pState + 4; + + /* The results in the 4 accumulators are in 2.30 format. Convert to 1.31 + ** Then store the 4 outputs in the destination buffer. */ + *pDst++ = (q31_t) (acc0 << 1); + *pDst++ = (q31_t) (acc1 << 1); + *pDst++ = (q31_t) (acc2 << 1); + *pDst++ = (q31_t) (acc3 << 1); + + /* Decrement the samples loop counter */ + blkCnt--; + } + + + /* If the blockSize is not a multiple of 4, compute any remaining output samples here. + ** No loop unrolling is used. */ + blkCnt = blockSize % 4u; + + while(blkCnt > 0u) + { + /* Copy one sample at a time into state buffer */ + *pStateCurnt++ = *pSrc++; + + /* Set the accumulator to zero */ + acc0 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize Coefficient pointer */ + pb = (pCoeffs); + + i = numTaps; + + /* Perform the multiply-accumulates */ + do + { + multAcc_32x32_keep32_R(acc0, (*px++), (*(pb++))); + i--; + } while(i > 0u); + + /* The result is in 2.30 format. Convert to 1.31 + ** Then store the output in the destination buffer. */ + *pDst++ = (q31_t) (acc0 << 1); + + /* Advance state pointer by 1 for the next sample */ + pState = pState + 1; + + /* Decrement the samples 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 state buffer */ + pStateCurnt = S->pState; + + /* Calculate remaining number of copies */ + tapCnt = (numTaps - 1u); + + /* Copy the remaining q31_t data */ + while(tapCnt > 0u) + { + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + tapCnt--; + } + + +} +IAR_ONLY_LOW_OPTIMIZATION_EXIT +/** + * @} end of FIR group + */ |