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/* ----------------------------------------------------------------------
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* Copyright (C) 2010 ARM Limited. All rights reserved.
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*
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* $Date: 15. July 2011
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* $Revision: V1.0.10
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*
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* Project: CMSIS DSP Library
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* Title: arm_fir_lattice_f32.c
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*
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* Description: Processing function for the floating-point FIR Lattice filter.
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*
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* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
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*
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* Version 1.0.10 2011/7/15
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* Big Endian support added and Merged M0 and M3/M4 Source code.
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*
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* Version 1.0.3 2010/11/29
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* Re-organized the CMSIS folders and updated documentation.
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*
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* Version 1.0.2 2010/11/11
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* Documentation updated.
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*
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* Version 1.0.1 2010/10/05
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* Production release and review comments incorporated.
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*
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* Version 1.0.0 2010/09/20
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* Production release and review comments incorporated
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*
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* Version 0.0.7 2010/06/10
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* Misra-C changes done
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* -------------------------------------------------------------------- */
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#include "arm_math.h"
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/**
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* @ingroup groupFilters
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*/
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/**
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* @defgroup FIR_Lattice Finite Impulse Response (FIR) Lattice Filters
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*
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* This set of functions implements Finite Impulse Response (FIR) lattice filters
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* for Q15, Q31 and floating-point data types. Lattice filters are used in a
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* variety of adaptive filter applications. The filter structure is feedforward and
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* the net impulse response is finite length.
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* The functions operate on blocks
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* of input and output data and each call to the function processes
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* <code>blockSize</code> samples through the filter. <code>pSrc</code> and
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* <code>pDst</code> point to input and output arrays containing <code>blockSize</code> values.
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*
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* \par Algorithm:
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* \image html FIRLattice.gif "Finite Impulse Response Lattice filter"
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* The following difference equation is implemented:
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* <pre>
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* f0[n] = g0[n] = x[n]
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* fm[n] = fm-1[n] + km * gm-1[n-1] for m = 1, 2, ...M
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* gm[n] = km * fm-1[n] + gm-1[n-1] for m = 1, 2, ...M
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* y[n] = fM[n]
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* </pre>
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* \par
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* <code>pCoeffs</code> points to tha array of reflection coefficients of size <code>numStages</code>.
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* Reflection Coefficients are stored in the following order.
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* \par
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* <pre>
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* {k1, k2, ..., kM}
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* </pre>
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* where M is number of stages
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* \par
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* <code>pState</code> points to a state array of size <code>numStages</code>.
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* The state variables (g values) hold previous inputs and are stored in the following order.
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* <pre>
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* {g0[n], g1[n], g2[n] ...gM-1[n]}
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* </pre>
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* The state variables are updated after each block of data is processed; the coefficients are untouched.
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* \par Instance Structure
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* The coefficients and state variables for a filter are stored together in an instance data structure.
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* A separate instance structure must be defined for each filter.
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* Coefficient arrays may be shared among several instances while state variable arrays cannot be shared.
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* There are separate instance structure declarations for each of the 3 supported data types.
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*
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* \par Initialization Functions
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* There is also an associated initialization function for each data type.
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* The initialization function performs the following operations:
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* - Sets the values of the internal structure fields.
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* - Zeros out the values in the state buffer.
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*
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* \par
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* Use of the initialization function is optional.
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* However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
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* To place an instance structure into a const data section, the instance structure must be manually initialized.
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* Set the values in the state buffer to zeros and then manually initialize the instance structure as follows:
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* <pre>
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*arm_fir_lattice_instance_f32 S = {numStages, pState, pCoeffs};
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*arm_fir_lattice_instance_q31 S = {numStages, pState, pCoeffs};
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*arm_fir_lattice_instance_q15 S = {numStages, pState, pCoeffs};
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* </pre>
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* \par
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* where <code>numStages</code> is the number of stages in the filter; <code>pState</code> is the address of the state buffer;
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* <code>pCoeffs</code> is the address of the coefficient buffer.
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* \par Fixed-Point Behavior
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* Care must be taken when using the fixed-point versions of the FIR Lattice filter functions.
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* In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
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* Refer to the function specific documentation below for usage guidelines.
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*/
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/**
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* @addtogroup FIR_Lattice
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* @{
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*/
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/**
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* @brief Processing function for the floating-point FIR lattice filter.
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* @param[in] *S points to an instance of the floating-point FIR lattice structure.
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* @param[in] *pSrc points to the block of input data.
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* @param[out] *pDst points to the block of output data
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* @param[in] blockSize number of samples to process.
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* @return none.
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*/
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void arm_fir_lattice_f32(
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const arm_fir_lattice_instance_f32 * S,
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float32_t * pSrc,
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float32_t * pDst,
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uint32_t blockSize)
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{
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float32_t *pState; /* State pointer */
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float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
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float32_t *px; /* temporary state pointer */
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float32_t *pk; /* temporary coefficient pointer */
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#ifndef ARM_MATH_CM0
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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float32_t fcurr1, fnext1, gcurr1, gnext1; /* temporary variables for first sample in loop unrolling */
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float32_t fcurr2, fnext2, gnext2; /* temporary variables for second sample in loop unrolling */
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float32_t fcurr3, fnext3, gnext3; /* temporary variables for third sample in loop unrolling */
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float32_t fcurr4, fnext4, gnext4; /* temporary variables for fourth sample in loop unrolling */
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uint32_t numStages = S->numStages; /* Number of stages in the filter */
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uint32_t blkCnt, stageCnt; /* temporary variables for counts */
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gcurr1 = 0.0f;
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pState = &S->pState[0];
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blkCnt = blockSize >> 2;
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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a second loop below computes the remaining 1 to 3 samples. */
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while(blkCnt > 0u)
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{
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/* Read two samples from input buffer */
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/* f0(n) = x(n) */
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fcurr1 = *pSrc++;
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fcurr2 = *pSrc++;
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/* Initialize coeff pointer */
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pk = (pCoeffs);
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/* Initialize state pointer */
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px = pState;
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/* Read g0(n-1) from state */
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gcurr1 = *px;
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/* Process first sample for first tap */
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/* f1(n) = f0(n) + K1 * g0(n-1) */
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fnext1 = fcurr1 + ((*pk) * gcurr1);
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext1 = (fcurr1 * (*pk)) + gcurr1;
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/* Process second sample for first tap */
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/* for sample 2 processing */
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fnext2 = fcurr2 + ((*pk) * fcurr1);
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gnext2 = (fcurr2 * (*pk)) + fcurr1;
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/* Read next two samples from input buffer */
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/* f0(n+2) = x(n+2) */
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fcurr3 = *pSrc++;
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fcurr4 = *pSrc++;
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/* Copy only last input samples into the state buffer
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which will be used for next four samples processing */
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*px++ = fcurr4;
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/* Process third sample for first tap */
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fnext3 = fcurr3 + ((*pk) * fcurr2);
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gnext3 = (fcurr3 * (*pk)) + fcurr2;
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/* Process fourth sample for first tap */
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fnext4 = fcurr4 + ((*pk) * fcurr3);
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gnext4 = (fcurr4 * (*pk++)) + fcurr3;
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/* Update of f values for next coefficient set processing */
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fcurr1 = fnext1;
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fcurr2 = fnext2;
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fcurr3 = fnext3;
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fcurr4 = fnext4;
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/* Loop unrolling. Process 4 taps at a time . */
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stageCnt = (numStages - 1u) >> 2u;
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/* Loop over the number of taps. Unroll by a factor of 4.
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** Repeat until we've computed numStages-3 coefficients. */
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/* Process 2nd, 3rd, 4th and 5th taps ... here */
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while(stageCnt > 0u)
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{
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/* Read g1(n-1), g3(n-1) .... from state */
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gcurr1 = *px;
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/* save g1(n) in state buffer */
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*px++ = gnext4;
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/* Process first sample for 2nd, 6th .. tap */
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/* Sample processing for K2, K6.... */
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/* f2(n) = f1(n) + K2 * g1(n-1) */
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fnext1 = fcurr1 + ((*pk) * gcurr1);
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/* Process second sample for 2nd, 6th .. tap */
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/* for sample 2 processing */
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fnext2 = fcurr2 + ((*pk) * gnext1);
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/* Process third sample for 2nd, 6th .. tap */
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fnext3 = fcurr3 + ((*pk) * gnext2);
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/* Process fourth sample for 2nd, 6th .. tap */
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fnext4 = fcurr4 + ((*pk) * gnext3);
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/* g2(n) = f1(n) * K2 + g1(n-1) */
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/* Calculation of state values for next stage */
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gnext4 = (fcurr4 * (*pk)) + gnext3;
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gnext3 = (fcurr3 * (*pk)) + gnext2;
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gnext2 = (fcurr2 * (*pk)) + gnext1;
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gnext1 = (fcurr1 * (*pk++)) + gcurr1;
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/* Read g2(n-1), g4(n-1) .... from state */
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gcurr1 = *px;
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/* save g2(n) in state buffer */
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*px++ = gnext4;
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/* Sample processing for K3, K7.... */
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/* Process first sample for 3rd, 7th .. tap */
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/* f3(n) = f2(n) + K3 * g2(n-1) */
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fcurr1 = fnext1 + ((*pk) * gcurr1);
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/* Process second sample for 3rd, 7th .. tap */
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fcurr2 = fnext2 + ((*pk) * gnext1);
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/* Process third sample for 3rd, 7th .. tap */
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fcurr3 = fnext3 + ((*pk) * gnext2);
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/* Process fourth sample for 3rd, 7th .. tap */
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fcurr4 = fnext4 + ((*pk) * gnext3);
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/* Calculation of state values for next stage */
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/* g3(n) = f2(n) * K3 + g2(n-1) */
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gnext4 = (fnext4 * (*pk)) + gnext3;
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gnext3 = (fnext3 * (*pk)) + gnext2;
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gnext2 = (fnext2 * (*pk)) + gnext1;
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gnext1 = (fnext1 * (*pk++)) + gcurr1;
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/* Read g1(n-1), g3(n-1) .... from state */
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gcurr1 = *px;
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/* save g3(n) in state buffer */
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*px++ = gnext4;
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/* Sample processing for K4, K8.... */
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/* Process first sample for 4th, 8th .. tap */
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/* f4(n) = f3(n) + K4 * g3(n-1) */
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fnext1 = fcurr1 + ((*pk) * gcurr1);
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/* Process second sample for 4th, 8th .. tap */
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/* for sample 2 processing */
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fnext2 = fcurr2 + ((*pk) * gnext1);
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/* Process third sample for 4th, 8th .. tap */
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fnext3 = fcurr3 + ((*pk) * gnext2);
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/* Process fourth sample for 4th, 8th .. tap */
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fnext4 = fcurr4 + ((*pk) * gnext3);
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/* g4(n) = f3(n) * K4 + g3(n-1) */
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/* Calculation of state values for next stage */
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gnext4 = (fcurr4 * (*pk)) + gnext3;
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gnext3 = (fcurr3 * (*pk)) + gnext2;
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gnext2 = (fcurr2 * (*pk)) + gnext1;
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gnext1 = (fcurr1 * (*pk++)) + gcurr1;
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/* Read g2(n-1), g4(n-1) .... from state */
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gcurr1 = *px;
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/* save g4(n) in state buffer */
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*px++ = gnext4;
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/* Sample processing for K5, K9.... */
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/* Process first sample for 5th, 9th .. tap */
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/* f5(n) = f4(n) + K5 * g4(n-1) */
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fcurr1 = fnext1 + ((*pk) * gcurr1);
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/* Process second sample for 5th, 9th .. tap */
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fcurr2 = fnext2 + ((*pk) * gnext1);
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/* Process third sample for 5th, 9th .. tap */
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fcurr3 = fnext3 + ((*pk) * gnext2);
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/* Process fourth sample for 5th, 9th .. tap */
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fcurr4 = fnext4 + ((*pk) * gnext3);
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/* Calculation of state values for next stage */
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/* g5(n) = f4(n) * K5 + g4(n-1) */
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gnext4 = (fnext4 * (*pk)) + gnext3;
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gnext3 = (fnext3 * (*pk)) + gnext2;
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gnext2 = (fnext2 * (*pk)) + gnext1;
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gnext1 = (fnext1 * (*pk++)) + gcurr1;
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stageCnt--;
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}
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/* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
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stageCnt = (numStages - 1u) % 0x4u;
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while(stageCnt > 0u)
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{
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gcurr1 = *px;
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/* save g value in state buffer */
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*px++ = gnext4;
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/* Process four samples for last three taps here */
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fnext1 = fcurr1 + ((*pk) * gcurr1);
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fnext2 = fcurr2 + ((*pk) * gnext1);
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fnext3 = fcurr3 + ((*pk) * gnext2);
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fnext4 = fcurr4 + ((*pk) * gnext3);
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext4 = (fcurr4 * (*pk)) + gnext3;
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gnext3 = (fcurr3 * (*pk)) + gnext2;
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gnext2 = (fcurr2 * (*pk)) + gnext1;
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gnext1 = (fcurr1 * (*pk++)) + gcurr1;
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/* Update of f values for next coefficient set processing */
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fcurr1 = fnext1;
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fcurr2 = fnext2;
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fcurr3 = fnext3;
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fcurr4 = fnext4;
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stageCnt--;
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}
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/* The results in the 4 accumulators, store in the destination buffer. */
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/* y(n) = fN(n) */
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*pDst++ = fcurr1;
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*pDst++ = fcurr2;
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*pDst++ = fcurr3;
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*pDst++ = fcurr4;
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x4u;
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while(blkCnt > 0u)
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{
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/* f0(n) = x(n) */
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fcurr1 = *pSrc++;
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/* Initialize coeff pointer */
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pk = (pCoeffs);
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/* Initialize state pointer */
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px = pState;
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/* read g2(n) from state buffer */
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gcurr1 = *px;
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/* for sample 1 processing */
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/* f1(n) = f0(n) + K1 * g0(n-1) */
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fnext1 = fcurr1 + ((*pk) * gcurr1);
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/* g1(n) = f0(n) * K1 + g0(n-1) */
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gnext1 = (fcurr1 * (*pk++)) + gcurr1;
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/* save g1(n) in state buffer */
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*px++ = fcurr1;
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/* f1(n) is saved in fcurr1
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for next stage processing */
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fcurr1 = fnext1;
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stageCnt = (numStages - 1u);
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/* stage loop */
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while(stageCnt > 0u)
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{
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/* read g2(n) from state buffer */
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gcurr1 = *px;
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|
|
|
|
/* 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 */
|
|
|
|
|
|
}
|
|
|
|
|
|
/**
|
|
|
* @} end of FIR_Lattice group
|
|
|
*/
|
|
|
|
