/* ----------------------------------------------------------------------
* 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_lattice_f32.c
*
* Description: Processing function for the floating-point FIR Lattice filter.
*
* 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;
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @defgroup FIR_Lattice Finite Impulse Response (FIR) Lattice Filters
*
* This set of functions implements Finite Impulse Response (FIR) lattice filters
* for Q15, Q31 and floating-point data types. Lattice filters are used in a
* variety of adaptive filter applications. The filter structure is feedforward and
* the net impulse response is finite length.
* The functions operate on blocks
* of input and output data and each call to the function processes
* blockSize samples through the filter. pSrc and
* pDst point to input and output arrays containing blockSize values.
*
* \par Algorithm:
* \image html FIRLattice.gif "Finite Impulse Response Lattice filter"
* The following difference equation is implemented:
*
* f0[n] = g0[n] = x[n]
* fm[n] = fm-1[n] + km * gm-1[n-1] for m = 1, 2, ...M
* gm[n] = km * fm-1[n] + gm-1[n-1] for m = 1, 2, ...M
* y[n] = fM[n]
*
* \par
* pCoeffs points to tha array of reflection coefficients of size numStages.
* Reflection Coefficients are stored in the following order.
* \par
*
* {k1, k2, ..., kM}
*
* where M is number of stages
* \par
* pState points to a state array of size numStages.
* The state variables (g values) hold previous inputs and are stored in the following order.
*
* {g0[n], g1[n], g2[n] ...gM-1[n]}
*
* The state variables are updated after each block of data is processed; the coefficients are untouched.
* \par Instance Structure
* The coefficients and state variables for a filter are stored together in an instance data structure.
* A separate instance structure must be defined for each filter.
* Coefficient arrays may be shared among several instances while state variable arrays cannot be shared.
* There are separate instance structure declarations for each of the 3 supported data types.
*
* \par Initialization Functions
* There is also an associated initialization function for each data type.
* The initialization function performs the following operations:
* - Sets the values of the internal structure fields.
* - Zeros out the values in the state buffer.
* To do this manually without calling the init function, assign the follow subfields of the instance structure:
* numStages, pCoeffs, pState. Also set all of the values in pState to zero.
*
* \par
* Use of the initialization function is optional.
* However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
* To place an instance structure into a const data section, the instance structure must be manually initialized.
* Set the values in the state buffer to zeros and then manually initialize the instance structure as follows:
*
*arm_fir_lattice_instance_f32 S = {numStages, pState, pCoeffs};
*arm_fir_lattice_instance_q31 S = {numStages, pState, pCoeffs};
*arm_fir_lattice_instance_q15 S = {numStages, pState, pCoeffs};
*
* \par
* where numStages is the number of stages in the filter; pState is the address of the state buffer;
* pCoeffs is the address of the coefficient buffer.
* \par Fixed-Point Behavior
* Care must be taken when using the fixed-point versions of the FIR Lattice filter functions.
* In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
* Refer to the function specific documentation below for usage guidelines.
*/
/**
* @addtogroup FIR_Lattice
* @{
*/
/**
* @brief Processing function for the floating-point FIR lattice filter.
* @param[in] *S points to an instance of the floating-point 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.
*/
void arm_fir_lattice_f32(
const arm_fir_lattice_instance_f32 * S,
float32_t * pSrc,
float32_t * pDst,
uint32_t blockSize)
{
float32_t *pState; /* State pointer */
float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
float32_t *px; /* temporary state pointer */
float32_t *pk; /* temporary coefficient pointer */
#ifndef ARM_MATH_CM0_FAMILY
/* Run the below code for Cortex-M4 and Cortex-M3 */
float32_t fcurr1, fnext1, gcurr1, gnext1; /* temporary variables for first sample in loop unrolling */
float32_t fcurr2, fnext2, gnext2; /* temporary variables for second sample in loop unrolling */
float32_t fcurr3, fnext3, gnext3; /* temporary variables for third sample in loop unrolling */
float32_t fcurr4, fnext4, gnext4; /* temporary variables for fourth sample in loop unrolling */
uint32_t numStages = S->numStages; /* Number of stages in the filter */
uint32_t blkCnt, stageCnt; /* temporary variables for counts */
gcurr1 = 0.0f;
pState = &S->pState[0];
blkCnt = blockSize >> 2;
/* 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)
{
/* Read two samples from input buffer */
/* f0(n) = x(n) */
fcurr1 = *pSrc++;
fcurr2 = *pSrc++;
/* Initialize coeff pointer */
pk = (pCoeffs);
/* Initialize state pointer */
px = pState;
/* Read g0(n-1) from state */
gcurr1 = *px;
/* Process first sample for first tap */
/* f1(n) = f0(n) + K1 * g0(n-1) */
fnext1 = fcurr1 + ((*pk) * gcurr1);
/* g1(n) = f0(n) * K1 + g0(n-1) */
gnext1 = (fcurr1 * (*pk)) + gcurr1;
/* Process second sample for first tap */
/* for sample 2 processing */
fnext2 = fcurr2 + ((*pk) * fcurr1);
gnext2 = (fcurr2 * (*pk)) + fcurr1;
/* Read next two samples from input buffer */
/* f0(n+2) = x(n+2) */
fcurr3 = *pSrc++;
fcurr4 = *pSrc++;
/* Copy only last input samples into the state buffer
which will be used for next four samples processing */
*px++ = fcurr4;
/* Process third sample for first tap */
fnext3 = fcurr3 + ((*pk) * fcurr2);
gnext3 = (fcurr3 * (*pk)) + fcurr2;
/* Process fourth sample for first tap */
fnext4 = fcurr4 + ((*pk) * fcurr3);
gnext4 = (fcurr4 * (*pk++)) + fcurr3;
/* Update of f values for next coefficient set processing */
fcurr1 = fnext1;
fcurr2 = fnext2;
fcurr3 = fnext3;
fcurr4 = fnext4;
/* Loop unrolling. Process 4 taps at a time . */
stageCnt = (numStages - 1u) >> 2u;
/* Loop over the number of taps. Unroll by a factor of 4.
** Repeat until we've computed numStages-3 coefficients. */
/* Process 2nd, 3rd, 4th and 5th taps ... here */
while(stageCnt > 0u)
{
/* Read g1(n-1), g3(n-1) .... from state */
gcurr1 = *px;
/* save g1(n) in state buffer */
*px++ = gnext4;
/* Process first sample for 2nd, 6th .. tap */
/* Sample processing for K2, K6.... */
/* f2(n) = f1(n) + K2 * g1(n-1) */
fnext1 = fcurr1 + ((*pk) * gcurr1);
/* Process second sample for 2nd, 6th .. tap */
/* for sample 2 processing */
fnext2 = fcurr2 + ((*pk) * gnext1);
/* Process third sample for 2nd, 6th .. tap */
fnext3 = fcurr3 + ((*pk) * gnext2);
/* Process fourth sample for 2nd, 6th .. tap */
fnext4 = fcurr4 + ((*pk) * gnext3);
/* g2(n) = f1(n) * K2 + g1(n-1) */
/* Calculation of state values for next stage */
gnext4 = (fcurr4 * (*pk)) + gnext3;
gnext3 = (fcurr3 * (*pk)) + gnext2;
gnext2 = (fcurr2 * (*pk)) + gnext1;
gnext1 = (fcurr1 * (*pk++)) + gcurr1;
/* Read g2(n-1), g4(n-1) .... from state */
gcurr1 = *px;
/* save g2(n) in state buffer */
*px++ = gnext4;
/* Sample processing for K3, K7.... */
/* Process first sample for 3rd, 7th .. tap */
/* f3(n) = f2(n) + K3 * g2(n-1) */
fcurr1 = fnext1 + ((*pk) * gcurr1);
/* Process second sample for 3rd, 7th .. tap */
fcurr2 = fnext2 + ((*pk) * gnext1);
/* Process third sample for 3rd, 7th .. tap */
fcurr3 = fnext3 + ((*pk) * gnext2);
/* Process fourth sample for 3rd, 7th .. tap */
fcurr4 = fnext4 + ((*pk) * gnext3);
/* Calculation of state values for next stage */
/* g3(n) = f2(n) * K3 + g2(n-1) */
gnext4 = (fnext4 * (*pk)) + gnext3;
gnext3 = (fnext3 * (*pk)) + gnext2;
gnext2 = (fnext2 * (*pk)) + gnext1;
gnext1 = (fnext1 * (*pk++)) + gcurr1;
/* Read g1(n-1), g3(n-1) .... from state */
gcurr1 = *px;
/* save g3(n) in state buffer */
*px++ = gnext4;
/* Sample processing for K4, K8.... */
/* Process first sample for 4th, 8th .. tap */
/* f4(n) = f3(n) + K4 * g3(n-1) */
fnext1 = fcurr1 + ((*pk) * gcurr1);
/* Process second sample for 4th, 8th .. tap */
/* for sample 2 processing */
fnext2 = fcurr2 + ((*pk) * gnext1);
/* Process third sample for 4th, 8th .. tap */
fnext3 = fcurr3 + ((*pk) * gnext2);
/* Process fourth sample for 4th, 8th .. tap */
fnext4 = fcurr4 + ((*pk) * gnext3);
/* g4(n) = f3(n) * K4 + g3(n-1) */
/* Calculation of state values for next stage */
gnext4 = (fcurr4 * (*pk)) + gnext3;
gnext3 = (fcurr3 * (*pk)) + gnext2;
gnext2 = (fcurr2 * (*pk)) + gnext1;
gnext1 = (fcurr1 * (*pk++)) + gcurr1;
/* Read g2(n-1), g4(n-1) .... from state */
gcurr1 = *px;
/* save g4(n) in state buffer */
*px++ = gnext4;
/* Sample processing for K5, K9.... */
/* Process first sample for 5th, 9th .. tap */
/* f5(n) = f4(n) + K5 * g4(n-1) */
fcurr1 = fnext1 + ((*pk) * gcurr1);
/* Process second sample for 5th, 9th .. tap */
fcurr2 = fnext2 + ((*pk) * gnext1);
/* Process third sample for 5th, 9th .. tap */
fcurr3 = fnext3 + ((*pk) * gnext2);
/* Process fourth sample for 5th, 9th .. tap */
fcurr4 = fnext4 + ((*pk) * gnext3);
/* Calculation of state values for next stage */
/* g5(n) = f4(n) * K5 + g4(n-1) */
gnext4 = (fnext4 * (*pk)) + gnext3;
gnext3 = (fnext3 * (*pk)) + gnext2;
gnext2 = (fnext2 * (*pk)) + gnext1;
gnext1 = (fnext1 * (*pk++)) + gcurr1;
stageCnt--;
}
/* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
stageCnt = (numStages - 1u) % 0x4u;
while(stageCnt > 0u)
{
gcurr1 = *px;
/* save g value in state buffer */
*px++ = gnext4;
/* Process four samples for last three taps here */
fnext1 = fcurr1 + ((*pk) * gcurr1);
fnext2 = fcurr2 + ((*pk) * gnext1);
fnext3 = fcurr3 + ((*pk) * gnext2);
fnext4 = fcurr4 + ((*pk) * gnext3);
/* g1(n) = f0(n) * K1 + g0(n-1) */
gnext4 = (fcurr4 * (*pk)) + gnext3;
gnext3 = (fcurr3 * (*pk)) + gnext2;
gnext2 = (fcurr2 * (*pk)) + gnext1;
gnext1 = (fcurr1 * (*pk++)) + gcurr1;
/* Update of f values for next coefficient set processing */
fcurr1 = fnext1;
fcurr2 = fnext2;
fcurr3 = fnext3;
fcurr4 = fnext4;
stageCnt--;
}
/* The results in the 4 accumulators, store in the destination buffer. */
/* y(n) = fN(n) */
*pDst++ = fcurr1;
*pDst++ = fcurr2;
*pDst++ = fcurr3;
*pDst++ = fcurr4;
blkCnt--;
}
/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
** No loop unrolling is used. */
blkCnt = blockSize % 0x4u;
while(blkCnt > 0u)
{
/* f0(n) = x(n) */
fcurr1 = *pSrc++;
/* Initialize coeff pointer */
pk = (pCoeffs);
/* Initialize state pointer */
px = pState;
/* read g2(n) from state buffer */
gcurr1 = *px;
/* for sample 1 processing */
/* f1(n) = f0(n) + K1 * g0(n-1) */
fnext1 = fcurr1 + ((*pk) * gcurr1);
/* g1(n) = f0(n) * K1 + g0(n-1) */
gnext1 = (fcurr1 * (*pk++)) + gcurr1;
/* 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 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 = fcurr1 + ((*pk) * gcurr1);
/* g2(n) = f1(n) * K2 + g1(n-1) */
gnext1 = (fcurr1 * (*pk++)) + gcurr1;
/* 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 */
float32_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 = fcurr + ((*pk) * gcurr);
/* g1(n) = f0(n) * K1 + g0(n-1) */
gnext = (fcurr * (*pk++)) + gcurr;
/* save f0(n) in state buffer */
*px++ = fcurr;
/* f1(n) is saved in fcurr
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 = fcurr + ((*pk) * gcurr);
/* g2(n) = f1(n) * K2 + g1(n-1) */
gnext = (fcurr * (*pk++)) + 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
*/