arm_fir_f32.c
355 lines
| 12.0 KiB
| text/x-c
|
CLexer
|
r16 | /* ---------------------------------------------------------------------- | ||
* Copyright (C) 2010 ARM Limited. All rights reserved. | ||||
* | ||||
* $Date: 29. November 2010 | ||||
* $Revision: V1.0.3 | ||||
* | ||||
* Project: CMSIS DSP Library | ||||
* Title: arm_fir_f32.c | ||||
* | ||||
* Description: Floating-point FIR filter processing function. | ||||
* | ||||
* Target Processor: Cortex-M4/Cortex-M3 | ||||
* | ||||
* 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 0.0.5 2010/04/26 | ||||
* incorporated review comments and updated with latest CMSIS layer | ||||
* | ||||
* Version 0.0.3 2010/03/10 | ||||
* Initial version | ||||
* -------------------------------------------------------------------- */ | ||||
#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 | ||||
* <code>blockSize</code> samples through the filter. <code>pSrc</code> and | ||||
* <code>pDst</code> points to input and output arrays containing <code>blockSize</code> values. | ||||
* | ||||
* \par Algorithm: | ||||
* The FIR filter algorithm is based upon a sequence of multiply-accumulate (MAC) operations. | ||||
* Each filter coefficient <code>b[n]</code> is multiplied by a state variable which equals a previous input sample <code>x[n]</code>. | ||||
* <pre> | ||||
* y[n] = b[0] * x[n] + b[1] * x[n-1] + b[2] * x[n-2] + ...+ b[numTaps-1] * x[n-numTaps+1] | ||||
* </pre> | ||||
* \par | ||||
* \image html FIR.gif "Finite Impulse Response filter" | ||||
* \par | ||||
* <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>. | ||||
* Coefficients are stored in time reversed order. | ||||
* \par | ||||
* <pre> | ||||
* {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]} | ||||
* </pre> | ||||
* \par | ||||
* <code>pState</code> points to a state array of size <code>numTaps + blockSize - 1</code>. | ||||
* Samples in the state buffer are stored in the following order. | ||||
* \par | ||||
* <pre> | ||||
* {x[n-numTaps+1], x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2]....x[0], x[1], ..., x[blockSize-1]} | ||||
* </pre> | ||||
* \par | ||||
* Note that the length of the state buffer exceeds the length of the coefficient array by <code>blockSize-1</code>. | ||||
* 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. | ||||
* | ||||
* \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 | ||||
* <pre> | ||||
*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}; | ||||
* </pre> | ||||
* | ||||
* where <code>numTaps</code> is the number of filter coefficients in the filter; <code>pState</code> is the address of the state buffer; | ||||
* <code>pCoeffs</code> 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. | ||||
* | ||||
*/ | ||||
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; /* Accumulators */ | ||||
float32_t x0, x1, x2, x3, 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 */ | ||||
/* 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 4 output values simultaneously. | ||||
* The variables acc0 ... acc3 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 >> 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) | ||||
{ | ||||
/* 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; | ||||
/* Initialize state pointer */ | ||||
px = pState; | ||||
/* Initialize coeff pointer */ | ||||
pb = (pCoeffs); | ||||
/* Read the first three samples from the state buffer: x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */ | ||||
x0 = *px++; | ||||
x1 = *px++; | ||||
x2 = *px++; | ||||
/* Loop unrolling. Process 4 taps at a time. */ | ||||
tapCnt = numTaps >> 2u; | ||||
/* Loop over the number of taps. Unroll by a factor of 4. | ||||
** Repeat until we've computed numTaps-4 coefficients. */ | ||||
while(tapCnt > 0u) | ||||
{ | ||||
/* Read the b[numTaps-1] coefficient */ | ||||
c0 = *(pb++); | ||||
/* Read x[n-numTaps-3] sample */ | ||||
x3 = *(px++); | ||||
/* acc0 += b[numTaps-1] * x[n-numTaps] */ | ||||
acc0 += x0 * c0; | ||||
/* acc1 += b[numTaps-1] * x[n-numTaps-1] */ | ||||
acc1 += x1 * c0; | ||||
/* acc2 += b[numTaps-1] * x[n-numTaps-2] */ | ||||
acc2 += x2 * c0; | ||||
/* acc3 += b[numTaps-1] * x[n-numTaps-3] */ | ||||
acc3 += x3 * c0; | ||||
/* Read the b[numTaps-2] coefficient */ | ||||
c0 = *(pb++); | ||||
/* Read x[n-numTaps-4] sample */ | ||||
x0 = *(px++); | ||||
/* Perform the multiply-accumulate */ | ||||
acc0 += x1 * c0; | ||||
acc1 += x2 * c0; | ||||
acc2 += x3 * c0; | ||||
acc3 += x0 * c0; | ||||
/* Read the b[numTaps-3] coefficient */ | ||||
c0 = *(pb++); | ||||
/* Read x[n-numTaps-5] sample */ | ||||
x1 = *(px++); | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 += x2 * c0; | ||||
acc1 += x3 * c0; | ||||
acc2 += x0 * c0; | ||||
acc3 += x1 * c0; | ||||
/* Read the b[numTaps-4] coefficient */ | ||||
c0 = *(pb++); | ||||
/* Read x[n-numTaps-6] sample */ | ||||
x2 = *(px++); | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 += x3 * c0; | ||||
acc1 += x0 * c0; | ||||
acc2 += x1 * c0; | ||||
acc3 += x2 * c0; | ||||
tapCnt--; | ||||
} | ||||
/* If the filter length is not a multiple of 4, compute the remaining filter taps */ | ||||
tapCnt = numTaps % 0x4u; | ||||
while(tapCnt > 0u) | ||||
{ | ||||
/* Read coefficients */ | ||||
c0 = *(pb++); | ||||
/* Fetch 1 state variable */ | ||||
x3 = *(px++); | ||||
/* Perform the multiply-accumulates */ | ||||
acc0 += x0 * c0; | ||||
acc1 += x1 * c0; | ||||
acc2 += x2 * c0; | ||||
acc3 += x3 * c0; | ||||
/* Reuse the present sample states for next sample */ | ||||
x0 = x1; | ||||
x1 = x2; | ||||
x2 = x3; | ||||
/* Decrement the loop counter */ | ||||
tapCnt--; | ||||
} | ||||
/* Advance the state pointer by 4 to process the next group of 4 samples */ | ||||
pState = pState + 4; | ||||
/* The results in the 4 accumulators, store in the destination buffer. */ | ||||
*pDst++ = acc0; | ||||
*pDst++ = acc1; | ||||
*pDst++ = acc2; | ||||
*pDst++ = acc3; | ||||
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) | ||||
{ | ||||
/* 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 satrt 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--; | ||||
} | ||||
} | ||||
/** | ||||
* @} end of FIR group | ||||
*/ | ||||