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+/* ----------------------------------------------------------------------
+* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
+*
+* $Date: 12. March 2014
+* $Revision: V1.4.4
+*
+* 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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