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- /* ----------------------------------------------------------------------
- * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
- *
- * $Date: 17. January 2013
- * $Revision: V1.4.1
- *
- * Project: CMSIS DSP Library
- * Title: arm_fir_lattice_q31.c
- *
- * Description: Q31 FIR lattice 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_Lattice
- * @{
- */
-
-
- /**
- * @brief Processing function for the Q31 FIR lattice filter.
- * @param[in] *S points to an instance of the Q31 FIR lattice 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.
- * @return none.
- *
- * @details
- * <b>Scaling and Overflow Behavior:</b>
- * In order to avoid overflows the input signal must be scaled down by 2*log2(numStages) bits.
- */
-
- #ifndef ARM_MATH_CM0_FAMILY
-
- /* Run the below code for Cortex-M4 and Cortex-M3 */
-
- void arm_fir_lattice_q31(
- const arm_fir_lattice_instance_q31 * S,
- q31_t * pSrc,
- q31_t * pDst,
- uint32_t blockSize)
- {
- q31_t *pState; /* State pointer */
- q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
- q31_t *px; /* temporary state pointer */
- q31_t *pk; /* temporary coefficient pointer */
- q31_t fcurr1, fnext1, gcurr1 = 0, gnext1; /* temporary variables for first sample in loop unrolling */
- q31_t fcurr2, fnext2, gnext2; /* temporary variables for second sample in loop unrolling */
- uint32_t numStages = S->numStages; /* Length of the filter */
- uint32_t blkCnt, stageCnt; /* temporary variables for counts */
- q31_t k;
-
- pState = &S->pState[0];
-
- blkCnt = blockSize >> 1u;
-
- /* First part of the processing with loop unrolling. Compute 2 outputs at a time.
- a second loop below computes the remaining 1 sample. */
- while(blkCnt > 0u)
- {
- /* f0(n) = x(n) */
- fcurr1 = *pSrc++;
-
- /* f0(n) = x(n) */
- fcurr2 = *pSrc++;
-
- /* Initialize coeff pointer */
- pk = (pCoeffs);
-
- /* Initialize state pointer */
- px = pState;
-
- /* read g0(n - 1) from state buffer */
- gcurr1 = *px;
-
- /* Read the reflection coefficient */
- k = *pk++;
-
- /* for sample 1 processing */
- /* f1(n) = f0(n) + K1 * g0(n-1) */
- fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
-
- /* g1(n) = f0(n) * K1 + g0(n-1) */
- gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
- fnext1 = fcurr1 + (fnext1 << 1u);
- gnext1 = gcurr1 + (gnext1 << 1u);
-
- /* for sample 1 processing */
- /* f1(n) = f0(n) + K1 * g0(n-1) */
- fnext2 = (q31_t) (((q63_t) fcurr1 * k) >> 32);
-
- /* g1(n) = f0(n) * K1 + g0(n-1) */
- gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32);
- fnext2 = fcurr2 + (fnext2 << 1u);
- gnext2 = fcurr1 + (gnext2 << 1u);
-
- /* save g1(n) in state buffer */
- *px++ = fcurr2;
-
- /* f1(n) is saved in fcurr1
- for next stage processing */
- fcurr1 = fnext1;
- fcurr2 = fnext2;
-
- stageCnt = (numStages - 1u);
-
- /* stage loop */
- while(stageCnt > 0u)
- {
-
- /* Read the reflection coefficient */
- k = *pk++;
-
- /* read g2(n) from state buffer */
- gcurr1 = *px;
-
- /* save g1(n) in state buffer */
- *px++ = gnext2;
-
- /* Sample processing for K2, K3.... */
- /* f2(n) = f1(n) + K2 * g1(n-1) */
- fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
- fnext2 = (q31_t) (((q63_t) gnext1 * k) >> 32);
-
- fnext1 = fcurr1 + (fnext1 << 1u);
- fnext2 = fcurr2 + (fnext2 << 1u);
-
- /* g2(n) = f1(n) * K2 + g1(n-1) */
- gnext2 = (q31_t) (((q63_t) fcurr2 * (k)) >> 32);
- gnext2 = gnext1 + (gnext2 << 1u);
-
- /* g2(n) = f1(n) * K2 + g1(n-1) */
- gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
- gnext1 = gcurr1 + (gnext1 << 1u);
-
- /* f1(n) is saved in fcurr1
- for next stage processing */
- fcurr1 = fnext1;
- fcurr2 = fnext2;
-
- stageCnt--;
-
- }
-
- /* y(n) = fN(n) */
- *pDst++ = fcurr1;
- *pDst++ = fcurr2;
-
- blkCnt--;
-
- }
-
- /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
- ** No loop unrolling is used. */
- blkCnt = blockSize % 0x2u;
-
- while(blkCnt > 0u)
- {
- /* f0(n) = x(n) */
- fcurr1 = *pSrc++;
-
- /* Initialize coeff pointer */
- pk = (pCoeffs);
-
- /* Initialize state pointer */
- px = pState;
-
- /* read g0(n - 1) from state buffer */
- gcurr1 = *px;
-
- /* Read the reflection coefficient */
- k = *pk++;
-
- /* for sample 1 processing */
- /* f1(n) = f0(n) + K1 * g0(n-1) */
- fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
- fnext1 = fcurr1 + (fnext1 << 1u);
-
- /* g1(n) = f0(n) * K1 + g0(n-1) */
- gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
- gnext1 = gcurr1 + (gnext1 << 1u);
-
- /* save g1(n) in state buffer */
- *px++ = fcurr1;
-
- /* f1(n) is saved in fcurr1
- for next stage processing */
- fcurr1 = fnext1;
-
- stageCnt = (numStages - 1u);
-
- /* stage loop */
- while(stageCnt > 0u)
- {
- /* Read the reflection coefficient */
- k = *pk++;
-
- /* read g2(n) from state buffer */
- gcurr1 = *px;
-
- /* save g1(n) in state buffer */
- *px++ = gnext1;
-
- /* Sample processing for K2, K3.... */
- /* f2(n) = f1(n) + K2 * g1(n-1) */
- fnext1 = (q31_t) (((q63_t) gcurr1 * k) >> 32);
- fnext1 = fcurr1 + (fnext1 << 1u);
-
- /* g2(n) = f1(n) * K2 + g1(n-1) */
- gnext1 = (q31_t) (((q63_t) fcurr1 * (k)) >> 32);
- gnext1 = gcurr1 + (gnext1 << 1u);
-
- /* f1(n) is saved in fcurr1
- for next stage processing */
- fcurr1 = fnext1;
-
- stageCnt--;
-
- }
-
-
- /* y(n) = fN(n) */
- *pDst++ = fcurr1;
-
- blkCnt--;
-
- }
-
-
- }
-
-
- #else
-
- /* Run the below code for Cortex-M0 */
-
- void arm_fir_lattice_q31(
- const arm_fir_lattice_instance_q31 * S,
- q31_t * pSrc,
- q31_t * pDst,
- uint32_t blockSize)
- {
- q31_t *pState; /* State pointer */
- q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
- q31_t *px; /* temporary state pointer */
- q31_t *pk; /* temporary coefficient pointer */
- q31_t fcurr, fnext, gcurr, gnext; /* temporary variables */
- uint32_t numStages = S->numStages; /* Length of the filter */
- uint32_t blkCnt, stageCnt; /* temporary variables for counts */
-
- pState = &S->pState[0];
-
- blkCnt = blockSize;
-
- while(blkCnt > 0u)
- {
- /* f0(n) = x(n) */
- fcurr = *pSrc++;
-
- /* Initialize coeff pointer */
- pk = (pCoeffs);
-
- /* Initialize state pointer */
- px = pState;
-
- /* read g0(n-1) from state buffer */
- gcurr = *px;
-
- /* for sample 1 processing */
- /* f1(n) = f0(n) + K1 * g0(n-1) */
- fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr;
- /* g1(n) = f0(n) * K1 + g0(n-1) */
- gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr;
- /* save g1(n) in state buffer */
- *px++ = fcurr;
-
- /* f1(n) is saved in fcurr1
- for next stage processing */
- fcurr = fnext;
-
- stageCnt = (numStages - 1u);
-
- /* stage loop */
- while(stageCnt > 0u)
- {
- /* read g2(n) from state buffer */
- gcurr = *px;
-
- /* save g1(n) in state buffer */
- *px++ = gnext;
-
- /* Sample processing for K2, K3.... */
- /* f2(n) = f1(n) + K2 * g1(n-1) */
- fnext = (q31_t) (((q63_t) gcurr * (*pk)) >> 31) + fcurr;
- /* g2(n) = f1(n) * K2 + g1(n-1) */
- gnext = (q31_t) (((q63_t) fcurr * (*pk++)) >> 31) + gcurr;
-
- /* f1(n) is saved in fcurr1
- for next stage processing */
- fcurr = fnext;
-
- stageCnt--;
-
- }
-
- /* y(n) = fN(n) */
- *pDst++ = fcurr;
-
- blkCnt--;
-
- }
-
- }
-
- #endif /* #ifndef ARM_MATH_CM0_FAMILY */
-
-
- /**
- * @} end of FIR_Lattice group
- */
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