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Diffstat (limited to 'DSP_Lib/Source/FilteringFunctions/arm_fir_q31.c')
-rw-r--r-- | DSP_Lib/Source/FilteringFunctions/arm_fir_q31.c | 365 |
1 files changed, 365 insertions, 0 deletions
diff --git a/DSP_Lib/Source/FilteringFunctions/arm_fir_q31.c b/DSP_Lib/Source/FilteringFunctions/arm_fir_q31.c new file mode 100644 index 0000000..3536059 --- /dev/null +++ b/DSP_Lib/Source/FilteringFunctions/arm_fir_q31.c @@ -0,0 +1,365 @@ +/* ---------------------------------------------------------------------- +* 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_q31.c +* +* Description: Q31 FIR filter processing function. +* +* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 +* +* 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 FIR filter 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 samples to process per call. + * @return none. + * + * @details + * <b>Scaling and Overflow Behavior:</b> + * \par + * 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 clip. + * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits. + * After all multiply-accumulates are performed, the 2.62 accumulator is right shifted by 31 bits and saturated to 1.31 format to yield the final result. + * + * \par + * Refer to the function <code>arm_fir_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4. + */ + +void arm_fir_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 */ + + +#ifndef ARM_MATH_CM0_FAMILY + + /* Run the below code for Cortex-M4 and Cortex-M3 */ + + q31_t x0, x1, x2; /* 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 */ + q63_t acc0, acc1, acc2; /* Accumulators */ + uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ + uint32_t i, tapCnt, blkCnt, tapCntN3; /* Loop counters */ + + /* S->pState points to state array 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 / 3; + blockSize = blockSize - (3 * blkCnt); + + tapCnt = numTaps / 3; + tapCntN3 = numTaps - (3 * tapCnt); + + /* 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 three new input samples into the state buffer */ + *pStateCurnt++ = *pSrc++; + *pStateCurnt++ = *pSrc++; + *pStateCurnt++ = *pSrc++; + + /* Set all accumulators to zero */ + acc0 = 0; + acc1 = 0; + acc2 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize coefficient pointer */ + pb = pCoeffs; + + /* Read the first two samples from the state buffer: + * x[n-numTaps], x[n-numTaps-1] */ + x0 = *(px++); + x1 = *(px++); + + /* Loop unrolling. Process 3 taps at a time. */ + i = tapCnt; + + while(i > 0u) + { + /* Read the b[numTaps] coefficient */ + c0 = *pb; + + /* Read x[n-numTaps-2] sample */ + x2 = *(px++); + + /* Perform the multiply-accumulates */ + acc0 += ((q63_t) x0 * c0); + acc1 += ((q63_t) x1 * c0); + acc2 += ((q63_t) x2 * c0); + + /* Read the coefficient and state */ + c0 = *(pb + 1u); + x0 = *(px++); + + /* Perform the multiply-accumulates */ + acc0 += ((q63_t) x1 * c0); + acc1 += ((q63_t) x2 * c0); + acc2 += ((q63_t) x0 * c0); + + /* Read the coefficient and state */ + c0 = *(pb + 2u); + x1 = *(px++); + + /* update coefficient pointer */ + pb += 3u; + + /* Perform the multiply-accumulates */ + acc0 += ((q63_t) x2 * c0); + acc1 += ((q63_t) x0 * c0); + acc2 += ((q63_t) x1 * c0); + + /* Decrement the loop counter */ + i--; + } + + /* If the filter length is not a multiple of 3, compute the remaining filter taps */ + + i = tapCntN3; + + while(i > 0u) + { + /* Read coefficients */ + c0 = *(pb++); + + /* Fetch 1 state variable */ + x2 = *(px++); + + /* Perform the multiply-accumulates */ + acc0 += ((q63_t) x0 * c0); + acc1 += ((q63_t) x1 * c0); + acc2 += ((q63_t) x2 * c0); + + /* Reuse the present sample states for next sample */ + x0 = x1; + x1 = x2; + + /* Decrement the loop counter */ + i--; + } + + /* Advance the state pointer by 3 to process the next group of 3 samples */ + pState = pState + 3; + + /* The results in the 3 accumulators are in 2.30 format. Convert to 1.31 + ** Then store the 3 outputs in the destination buffer. */ + *pDst++ = (q31_t) (acc0 >> 31u); + *pDst++ = (q31_t) (acc1 >> 31u); + *pDst++ = (q31_t) (acc2 >> 31u); + + /* Decrement the samples loop counter */ + blkCnt--; + } + + /* If the blockSize is not a multiple of 3, compute any remaining output samples here. + ** No loop unrolling is used. */ + + while(blockSize > 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 + { + acc0 += (q63_t) * (px++) * (*(pb++)); + i--; + } while(i > 0u); + + /* The result is in 2.62 format. Convert to 1.31 + ** Then store the output in the destination buffer. */ + *pDst++ = (q31_t) (acc0 >> 31u); + + /* Advance state pointer by 1 for the next sample */ + pState = pState + 1; + + /* Decrement the samples loop counter */ + blockSize--; + } + + /* 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 */ + pStateCurnt = S->pState; + + 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 */ + + q31_t *px; /* Temporary pointer for state */ + q31_t *pb; /* Temporary pointer for coefficient buffer */ + q63_t acc; /* Accumulator */ + uint32_t numTaps = S->numTaps; /* Length of the filter */ + uint32_t i, tapCnt, blkCnt; /* Loop counters */ + + /* S->pState buffer contains previous frame (numTaps - 1) samples */ + /* pStateCurnt points to the location where the new input data should be written */ + pStateCurnt = &(S->pState[(numTaps - 1u)]); + + /* Initialize blkCnt with blockSize */ + blkCnt = blockSize; + + while(blkCnt > 0u) + { + /* Copy one sample at a time into state buffer */ + *pStateCurnt++ = *pSrc++; + + /* Set the accumulator to zero */ + acc = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize Coefficient pointer */ + pb = pCoeffs; + + i = numTaps; + + /* Perform the multiply-accumulates */ + do + { + /* acc = 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] */ + acc += (q63_t) * px++ * *pb++; + i--; + } while(i > 0u); + + /* The result is in 2.62 format. Convert to 1.31 + ** Then store the output in the destination buffer. */ + *pDst++ = (q31_t) (acc >> 31u); + + /* 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 starting 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; + + /* Copy numTaps number of values */ + tapCnt = numTaps - 1u; + + /* Copy the data */ + while(tapCnt > 0u) + { + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + tapCnt--; + } + + +#endif /* #ifndef ARM_MATH_CM0_FAMILY */ + +} + +/** + * @} end of FIR group + */ |