/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. February 2012
* $Revision: V1.1.0
*
* 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
*
* Version 1.1.0 2012/02/15
* Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
* Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
* Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
* Documentation updated.
*
* Version 1.0.1 2010/10/05
* Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
* Production release and review comments incorporated
*
* Version 0.0.7 2010/06/10
* Misra-C changes done
* -------------------------------------------------------------------- */
#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
/* 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 */
/**
* @} end of FIR_Lattice group
*/