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Diffstat (limited to 'platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_q31.c')
| -rw-r--r-- | platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_q31.c | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_q31.c b/platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_q31.c new file mode 100644 index 0000000..b85a690 --- /dev/null +++ b/platform/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_q31.c @@ -0,0 +1,311 @@ +/* ---------------------------------------------------------------------- +* Copyright (C) 2010-2014 ARM Limited. All rights reserved. +* +* $Date: 12. March 2014 +* $Revision: V1.4.4 +* +* Project: CMSIS DSP Library +* Title: arm_fir_decimate_q31.c +* +* Description: Q31 FIR Decimator. +* +* 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_decimate + * @{ + */ + +/** + * @brief Processing function for the Q31 FIR decimator. + * @param[in] *S points to an instance of the Q31 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 + * + * <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 (where log2 is read as log to the base 2). + * After all multiply-accumulates are performed, the 2.62 accumulator is truncated to 1.32 format and then saturated to 1.31 format. + * + * \par + * Refer to the function <code>arm_fir_decimate_fast_q31()</code> for a faster but less precise implementation of this function for Cortex-M3 and Cortex-M4. + */ + +void arm_fir_decimate_q31( + const arm_fir_decimate_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, c0; /* Temporary variables to hold state and coefficient values */ + q31_t *px; /* Temporary pointers for state buffer */ + q31_t *pb; /* Temporary pointers for coefficient buffer */ + q63_t sum0; /* Accumulator */ + uint32_t numTaps = S->numTaps; /* Number of taps */ + uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ + + +#ifndef ARM_MATH_CM0_FAMILY + + /* Run the below code for Cortex-M4 and Cortex-M3 */ + + /* 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); + + /* Total number of output samples to be computed */ + blkCnt = outBlockSize; + + while(blkCnt > 0u) + { + /* Copy decimation factor number of new input samples into the state buffer */ + i = S->M; + + do + { + *pStateCurnt++ = *pSrc++; + + } while(--i); + + /* Set accumulator to zero */ + sum0 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize coeff pointer */ + pb = pCoeffs; + + /* Loop unrolling. Process 4 taps at a time. */ + tapCnt = numTaps >> 2; + + /* Loop over the number of taps. Unroll by a factor of 4. + ** Repeat until we've computed numTaps-4 coefficients. */ + while(tapCnt > 0u) + { + /* Read the b[numTaps-1] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-1] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 += (q63_t) x0 *c0; + + /* Read the b[numTaps-2] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-2] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 += (q63_t) x0 *c0; + + /* Read the b[numTaps-3] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-3] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 += (q63_t) x0 *c0; + + /* Read the b[numTaps-4] coefficient */ + c0 = *(pb++); + + /* Read x[n-numTaps-4] sample */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 += (q63_t) x0 *c0; + + /* Decrement the loop counter */ + tapCnt--; + } + + /* If the filter length is not a multiple of 4, compute the remaining filter taps */ + tapCnt = numTaps % 0x4u; + + while(tapCnt > 0u) + { + /* Read coefficients */ + c0 = *(pb++); + + /* Fetch 1 state variable */ + x0 = *(px++); + + /* Perform the multiply-accumulate */ + sum0 += (q63_t) 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; + + /* The result is in the accumulator, store in the destination buffer. */ + *pDst++ = (q31_t) (sum0 >> 31); + + /* Decrement the loop counter */ + blkCnt--; + } + + /* 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; + + i = (numTaps - 1u) >> 2u; + + /* copy data */ + while(i > 0u) + { + *pStateCurnt++ = *pState++; + *pStateCurnt++ = *pState++; + *pStateCurnt++ = *pState++; + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + i--; + } + + i = (numTaps - 1u) % 0x04u; + + /* copy data */ + while(i > 0u) + { + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + i--; + } + +#else + +/* Run the below code for Cortex-M0 */ + + /* 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); + + /* Total number of output samples to be computed */ + blkCnt = outBlockSize; + + while(blkCnt > 0u) + { + /* Copy decimation factor number of new input samples into the state buffer */ + i = S->M; + + do + { + *pStateCurnt++ = *pSrc++; + + } while(--i); + + /* Set accumulator to zero */ + sum0 = 0; + + /* Initialize state pointer */ + px = pState; + + /* Initialize coeff pointer */ + pb = pCoeffs; + + tapCnt = numTaps; + + while(tapCnt > 0u) + { + /* Read coefficients */ + c0 = *pb++; + + /* Fetch 1 state variable */ + x0 = *px++; + + /* Perform the multiply-accumulate */ + sum0 += (q63_t) 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; + + /* The result is in the accumulator, store in the destination buffer. */ + *pDst++ = (q31_t) (sum0 >> 31); + + /* Decrement the 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; + + i = numTaps - 1u; + + /* copy data */ + while(i > 0u) + { + *pStateCurnt++ = *pState++; + + /* Decrement the loop counter */ + i--; + } + +#endif /* #ifndef ARM_MATH_CM0_FAMILY */ + +} + +/** + * @} end of FIR_decimate group + */ |