/* ----------------------------------------------------------------------
* Copyright (C) 2010-2013 ARM Limited. All rights reserved.
*
* $Date: 17. January 2013
* $Revision: V1.4.1
*
* Project: CMSIS DSP Library
* Title: arm_fir_f32.c
*
* Description: Floating-point FIR 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,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* -------------------------------------------------------------------- */
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @defgroup FIR Finite Impulse Response (FIR) Filters
*
* This set of functions implements Finite Impulse Response (FIR) filters
* for Q7, Q15, Q31, and floating-point data types. Fast versions of Q15 and Q31 are also provided.
* 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 points to input and output arrays containing blockSize values.
*
* \par Algorithm:
* The FIR filter algorithm is based upon a sequence of multiply-accumulate (MAC) operations.
* Each filter coefficient b[n] is multiplied by a state variable which equals a previous input sample x[n].
*
* y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1]
*
* \par
* \image html FIR.gif "Finite Impulse Response filter"
* \par
* pCoeffs points to a coefficient array of size numTaps.
* Coefficients are stored in time reversed order.
* \par
*
* {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}
*
* \par
* pState points to a state array of size numTaps + blockSize - 1.
* Samples in the state buffer are stored in the following order.
* \par
*
* {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]}
*
* \par
* Note that the length of the state buffer exceeds the length of the coefficient array by blockSize-1.
* The increased state buffer length allows circular addressing, which is traditionally used in the FIR filters,
* to be avoided and yields a significant speed improvement.
* 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 4 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:
* numTaps, 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 before static initialization.
* The code below statically initializes each of the 4 different data type filter instance structures
*
*arm_fir_instance_f32 S = {numTaps, pState, pCoeffs};
*arm_fir_instance_q31 S = {numTaps, pState, pCoeffs};
*arm_fir_instance_q15 S = {numTaps, pState, pCoeffs};
*arm_fir_instance_q7 S = {numTaps, pState, pCoeffs};
*
*
* where numTaps is the number of filter coefficients 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 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
* @{
*/
/**
*
* @param[in] *S points to an instance of the floating-point FIR filter 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 per call.
* @return none.
*
*/
#ifndef ARM_MATH_CM0_FAMILY
/* Run the below code for Cortex-M4 and Cortex-M3 */
void arm_fir_f32(
const arm_fir_instance_f32 * S,
float32_t * pSrc,
float32_t * pDst,
uint32_t blockSize)
{
float32_t *pState = S->pState; /* State pointer */
float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
float32_t *pStateCurnt; /* Points to the current sample of the state */
float32_t *px, *pb; /* Temporary pointers for state and coefficient buffers */
float32_t acc0, acc1, acc2, acc3, acc4, acc5, acc6, acc7; /* Accumulators */
float32_t x0, x1, x2, x3, x4, x5, x6, x7, c0; /* Temporary variables to hold state and coefficient values */
uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
uint32_t i, tapCnt, blkCnt; /* Loop counters */
float32_t p0,p1,p2,p3,p4,p5,p6,p7; /* Temporary product values */
/* S->pState points to state array which contains previous frame (numTaps - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = &(S->pState[(numTaps - 1u)]);
/* Apply loop unrolling and compute 8 output values simultaneously.
* The variables acc0 ... acc7 hold output values that are being computed:
*
* acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0]
* acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1]
* acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2]
* acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3]
*/
blkCnt = blockSize >> 3;
/* First part of the processing with loop unrolling. Compute 8 outputs at a time.
** a second loop below computes the remaining 1 to 7 samples. */
while(blkCnt > 0u)
{
/* Copy four new input samples into the state buffer */
*pStateCurnt++ = *pSrc++;
*pStateCurnt++ = *pSrc++;
*pStateCurnt++ = *pSrc++;
*pStateCurnt++ = *pSrc++;
/* Set all accumulators to zero */
acc0 = 0.0f;
acc1 = 0.0f;
acc2 = 0.0f;
acc3 = 0.0f;
acc4 = 0.0f;
acc5 = 0.0f;
acc6 = 0.0f;
acc7 = 0.0f;
/* Initialize state pointer */
px = pState;
/* Initialize coeff pointer */
pb = (pCoeffs);
/* This is separated from the others to avoid
* a call to __aeabi_memmove which would be slower
*/
*pStateCurnt++ = *pSrc++;
*pStateCurnt++ = *pSrc++;
*pStateCurnt++ = *pSrc++;
*pStateCurnt++ = *pSrc++;
/* Read the first seven samples from the state buffer: x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */
x0 = *px++;
x1 = *px++;
x2 = *px++;
x3 = *px++;
x4 = *px++;
x5 = *px++;
x6 = *px++;
/* Loop unrolling. Process 8 taps at a time. */
tapCnt = numTaps >> 3u;
/* Loop over the number of taps. Unroll by a factor of 8.
** Repeat until we've computed numTaps-8 coefficients. */
while(tapCnt > 0u)
{
/* Read the b[numTaps-1] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-3] sample */
x7 = *(px++);
/* acc0 += b[numTaps-1] * x[n-numTaps] */
p0 = x0 * c0;
/* acc1 += b[numTaps-1] * x[n-numTaps-1] */
p1 = x1 * c0;
/* acc2 += b[numTaps-1] * x[n-numTaps-2] */
p2 = x2 * c0;
/* acc3 += b[numTaps-1] * x[n-numTaps-3] */
p3 = x3 * c0;
/* acc4 += b[numTaps-1] * x[n-numTaps-4] */
p4 = x4 * c0;
/* acc1 += b[numTaps-1] * x[n-numTaps-5] */
p5 = x5 * c0;
/* acc2 += b[numTaps-1] * x[n-numTaps-6] */
p6 = x6 * c0;
/* acc3 += b[numTaps-1] * x[n-numTaps-7] */
p7 = x7 * c0;
/* Read the b[numTaps-2] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-4] sample */
x0 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulate */
p0 = x1 * c0;
p1 = x2 * c0;
p2 = x3 * c0;
p3 = x4 * c0;
p4 = x5 * c0;
p5 = x6 * c0;
p6 = x7 * c0;
p7 = x0 * c0;
/* Read the b[numTaps-3] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-5] sample */
x1 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulates */
p0 = x2 * c0;
p1 = x3 * c0;
p2 = x4 * c0;
p3 = x5 * c0;
p4 = x6 * c0;
p5 = x7 * c0;
p6 = x0 * c0;
p7 = x1 * c0;
/* Read the b[numTaps-4] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-6] sample */
x2 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulates */
p0 = x3 * c0;
p1 = x4 * c0;
p2 = x5 * c0;
p3 = x6 * c0;
p4 = x7 * c0;
p5 = x0 * c0;
p6 = x1 * c0;
p7 = x2 * c0;
/* Read the b[numTaps-4] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-6] sample */
x3 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulates */
p0 = x4 * c0;
p1 = x5 * c0;
p2 = x6 * c0;
p3 = x7 * c0;
p4 = x0 * c0;
p5 = x1 * c0;
p6 = x2 * c0;
p7 = x3 * c0;
/* Read the b[numTaps-4] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-6] sample */
x4 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulates */
p0 = x5 * c0;
p1 = x6 * c0;
p2 = x7 * c0;
p3 = x0 * c0;
p4 = x1 * c0;
p5 = x2 * c0;
p6 = x3 * c0;
p7 = x4 * c0;
/* Read the b[numTaps-4] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-6] sample */
x5 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulates */
p0 = x6 * c0;
p1 = x7 * c0;
p2 = x0 * c0;
p3 = x1 * c0;
p4 = x2 * c0;
p5 = x3 * c0;
p6 = x4 * c0;
p7 = x5 * c0;
/* Read the b[numTaps-4] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-6] sample */
x6 = *(px++);
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Perform the multiply-accumulates */
p0 = x7 * c0;
p1 = x0 * c0;
p2 = x1 * c0;
p3 = x2 * c0;
p4 = x3 * c0;
p5 = x4 * c0;
p6 = x5 * c0;
p7 = x6 * c0;
tapCnt--;
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
}
/* If the filter length is not a multiple of 8, compute the remaining filter taps */
tapCnt = numTaps % 0x8u;
while(tapCnt > 0u)
{
/* Read coefficients */
c0 = *(pb++);
/* Fetch 1 state variable */
x7 = *(px++);
/* Perform the multiply-accumulates */
p0 = x0 * c0;
p1 = x1 * c0;
p2 = x2 * c0;
p3 = x3 * c0;
p4 = x4 * c0;
p5 = x5 * c0;
p6 = x6 * c0;
p7 = x7 * c0;
/* Reuse the present sample states for next sample */
x0 = x1;
x1 = x2;
x2 = x3;
x3 = x4;
x4 = x5;
x5 = x6;
x6 = x7;
acc0 += p0;
acc1 += p1;
acc2 += p2;
acc3 += p3;
acc4 += p4;
acc5 += p5;
acc6 += p6;
acc7 += p7;
/* Decrement the loop counter */
tapCnt--;
}
/* Advance the state pointer by 8 to process the next group of 8 samples */
pState = pState + 8;
/* The results in the 8 accumulators, store in the destination buffer. */
*pDst++ = acc0;
*pDst++ = acc1;
*pDst++ = acc2;
*pDst++ = acc3;
*pDst++ = acc4;
*pDst++ = acc5;
*pDst++ = acc6;
*pDst++ = acc7;
blkCnt--;
}
/* If the blockSize is not a multiple of 8, compute any remaining output samples here.
** No loop unrolling is used. */
blkCnt = blockSize % 0x8u;
while(blkCnt > 0u)
{
/* Copy one sample at a time into state buffer */
*pStateCurnt++ = *pSrc++;
/* Set the accumulator to zero */
acc0 = 0.0f;
/* Initialize state pointer */
px = pState;
/* Initialize Coefficient pointer */
pb = (pCoeffs);
i = numTaps;
/* Perform the multiply-accumulates */
do
{
acc0 += *px++ * *pb++;
i--;
} while(i > 0u);
/* The result is store in the destination buffer. */
*pDst++ = acc0;
/* Advance state pointer by 1 for the next sample */
pState = pState + 1;
blkCnt--;
}
/* Processing is complete.
** Now copy the last numTaps - 1 samples to the start of the state buffer.
** This prepares the state buffer for the next function call. */
/* Points to the start of the state buffer */
pStateCurnt = S->pState;
tapCnt = (numTaps - 1u) >> 2u;
/* copy data */
while(tapCnt > 0u)
{
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
/* Calculate remaining number of copies */
tapCnt = (numTaps - 1u) % 0x4u;
/* Copy the remaining q31_t data */
while(tapCnt > 0u)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
}
#else
void arm_fir_f32(
const arm_fir_instance_f32 * S,
float32_t * pSrc,
float32_t * pDst,
uint32_t blockSize)
{
float32_t *pState = S->pState; /* State pointer */
float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
float32_t *pStateCurnt; /* Points to the current sample of the state */
float32_t *px, *pb; /* Temporary pointers for state and coefficient buffers */
uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
uint32_t i, tapCnt, blkCnt; /* Loop counters */
/* Run the below code for Cortex-M0 */
float32_t acc;
/* S->pState points to state array which contains previous frame (numTaps - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = &(S->pState[(numTaps - 1u)]);
/* Initialize blkCnt with blockSize */
blkCnt = blockSize;
while(blkCnt > 0u)
{
/* Copy one sample at a time into state buffer */
*pStateCurnt++ = *pSrc++;
/* Set the accumulator to zero */
acc = 0.0f;
/* Initialize state pointer */
px = pState;
/* Initialize Coefficient pointer */
pb = pCoeffs;
i = numTaps;
/* Perform the multiply-accumulates */
do
{
/* acc = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */
acc += *px++ * *pb++;
i--;
} while(i > 0u);
/* The result is store in the destination buffer. */
*pDst++ = acc;
/* Advance state pointer by 1 for the next sample */
pState = pState + 1;
blkCnt--;
}
/* Processing is complete.
** Now copy the last numTaps - 1 samples to the starting of the state buffer.
** This prepares the state buffer for the next function call. */
/* Points to the start of the state buffer */
pStateCurnt = S->pState;
/* Copy numTaps number of values */
tapCnt = numTaps - 1u;
/* Copy data */
while(tapCnt > 0u)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
tapCnt--;
}
}
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
/**
* @} end of FIR group
*/