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arm_fir_sparse_f32.c
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/ lib / src / stm32f4 / CPU / CMSIS / DSP_Lib / Source / FilteringFunctions / arm_fir_sparse_f32.c
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/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. July 2011
* $Revision: V1.0.10
*
* Project: CMSIS DSP Library
* Title: arm_fir_sparse_f32.c
*
* Description: Floating-point sparse FIR filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* 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
*/
/**
* @defgroup FIR_Sparse Finite Impulse Response (FIR) Sparse Filters
*
* This group of functions implements sparse FIR filters.
* Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero.
* Sparse filters are used for simulating reflections in communications and audio applications.
*
* There are separate functions for Q7, Q15, Q31, and floating-point data types.
* 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 respectively containing <code>blockSize</code> values.
*
* \par Algorithm:
* The sparse filter instant structure contains an array of tap indices <code>pTapDelay</code> which specifies the locations of the non-zero coefficients.
* This is in addition to the coefficient array <code>b</code>.
* The implementation essentially skips the multiplications by zero and leads to an efficient realization.
* <pre>
* y[n] = b[0] * x[n-pTapDelay[0]] + b[1] * x[n-pTapDelay[1]] + b[2] * x[n-pTapDelay[2]] + ...+ b[numTaps-1] * x[n-pTapDelay[numTaps-1]]
* </pre>
* \par
* \image html FIRSparse.gif "Sparse FIR filter. b[n] represents the filter coefficients"
* \par
* <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>;
* <code>pTapDelay</code> points to an array of nonzero indices and is also of size <code>numTaps</code>;
* <code>pState</code> points to a state array of size <code>maxDelay + blockSize</code>, where
* <code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array.
* Some of the processing functions also require temporary working buffers.
*
* \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 and offset 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_sparse_instance_f32 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
*arm_fir_sparse_instance_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
*arm_fir_sparse_instance_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
*arm_fir_sparse_instance_q7 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
* </pre>
* \par
*
* \par Fixed-Point Behavior
* Care must be taken when using the fixed-point versions of the sparse 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_Sparse
* @{
*/
/**
* @brief Processing function for the floating-point sparse FIR filter.
* @param[in] *S points to an instance of the floating-point sparse FIR structure.
* @param[in] *pSrc points to the block of input data.
* @param[out] *pDst points to the block of output data
* @param[in] *pScratchIn points to a temporary buffer of size blockSize.
* @param[in] blockSize number of input samples to process per call.
* @return none.
*/
void arm_fir_sparse_f32(
arm_fir_sparse_instance_f32 * S,
float32_t * pSrc,
float32_t * pDst,
float32_t * pScratchIn,
uint32_t blockSize)
{
float32_t *pState = S->pState; /* State pointer */
float32_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
float32_t *px; /* Scratch buffer pointer */
float32_t *py = pState; /* Temporary pointers for state buffer */
float32_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */
float32_t *pOut; /* Destination pointer */
int32_t *pTapDelay = S->pTapDelay; /* Pointer to the array containing offset of the non-zero tap values. */
uint32_t delaySize = S->maxDelay + blockSize; /* state length */
uint16_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
int32_t readIndex; /* Read index of the state buffer */
uint32_t tapCnt, blkCnt; /* loop counters */
float32_t coeff = *pCoeffs++; /* Read the first coefficient value */
/* BlockSize of Input samples are copied into the state buffer */
/* StateIndex points to the starting position to write in the state buffer */
arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1,
(int32_t *) pSrc, 1, blockSize);
/* Read Index, from where the state buffer should be read, is calculated. */
readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;
/* Wraparound of readIndex */
if(readIndex < 0)
{
readIndex += (int32_t) delaySize;
}
/* Working pointer for state buffer is updated */
py = pState;
/* blockSize samples are read from the state buffer */
arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
(int32_t *) pb, (int32_t *) pb, blockSize, 1,
blockSize);
/* Working pointer for the scratch buffer */
px = pb;
/* Working pointer for destination buffer */
pOut = pDst;
#ifndef ARM_MATH_CM0
/* Run the below code for Cortex-M4 and Cortex-M3 */
/* Loop over the blockSize. Unroll by a factor of 4.
* Compute 4 Multiplications at a time. */
blkCnt = blockSize >> 2u;
while(blkCnt > 0u)
{
/* Perform Multiplications and store in destination buffer */
*pOut++ = *px++ * coeff;
*pOut++ = *px++ * coeff;
*pOut++ = *px++ * coeff;
*pOut++ = *px++ * coeff;
/* Decrement the loop counter */
blkCnt--;
}
/* If the blockSize is not a multiple of 4,
* compute the remaining samples */
blkCnt = blockSize % 0x4u;
while(blkCnt > 0u)
{
/* Perform Multiplications and store in destination buffer */
*pOut++ = *px++ * coeff;
/* Decrement the loop counter */
blkCnt--;
}
/* Load the coefficient value and
* increment the coefficient buffer for the next set of state values */
coeff = *pCoeffs++;
/* Read Index, from where the state buffer should be read, is calculated. */
readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;
/* Wraparound of readIndex */
if(readIndex < 0)
{
readIndex += (int32_t) delaySize;
}
/* Loop over the number of taps. */
tapCnt = (uint32_t) numTaps - 1u;
while(tapCnt > 0u)
{
/* Working pointer for state buffer is updated */
py = pState;
/* blockSize samples are read from the state buffer */
arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
(int32_t *) pb, (int32_t *) pb, blockSize, 1,
blockSize);
/* Working pointer for the scratch buffer */
px = pb;
/* Working pointer for destination buffer */
pOut = pDst;
/* Loop over the blockSize. Unroll by a factor of 4.
* Compute 4 MACS at a time. */
blkCnt = blockSize >> 2u;
while(blkCnt > 0u)
{
/* Perform Multiply-Accumulate */
*pOut++ += *px++ * coeff;
*pOut++ += *px++ * coeff;
*pOut++ += *px++ * coeff;
*pOut++ += *px++ * coeff;
/* Decrement the loop counter */
blkCnt--;
}
/* If the blockSize is not a multiple of 4,
* compute the remaining samples */
blkCnt = blockSize % 0x4u;
while(blkCnt > 0u)
{
/* Perform Multiply-Accumulate */
*pOut++ += *px++ * coeff;
/* Decrement the loop counter */
blkCnt--;
}
/* Load the coefficient value and
* increment the coefficient buffer for the next set of state values */
coeff = *pCoeffs++;
/* Read Index, from where the state buffer should be read, is calculated. */
readIndex = ((int32_t) S->stateIndex -
(int32_t) blockSize) - *pTapDelay++;
/* Wraparound of readIndex */
if(readIndex < 0)
{
readIndex += (int32_t) delaySize;
}
/* Decrement the tap loop counter */
tapCnt--;
}
#else
/* Run the below code for Cortex-M0 */
blkCnt = blockSize;
while(blkCnt > 0u)
{
/* Perform Multiplications and store in destination buffer */
*pOut++ = *px++ * coeff;
/* Decrement the loop counter */
blkCnt--;
}
/* Load the coefficient value and
* increment the coefficient buffer for the next set of state values */
coeff = *pCoeffs++;
/* Read Index, from where the state buffer should be read, is calculated. */
readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;
/* Wraparound of readIndex */
if(readIndex < 0)
{
readIndex += (int32_t) delaySize;
}
/* Loop over the number of taps. */
tapCnt = (uint32_t) numTaps - 1u;
while(tapCnt > 0u)
{
/* Working pointer for state buffer is updated */
py = pState;
/* blockSize samples are read from the state buffer */
arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
(int32_t *) pb, (int32_t *) pb, blockSize, 1,
blockSize);
/* Working pointer for the scratch buffer */
px = pb;
/* Working pointer for destination buffer */
pOut = pDst;
blkCnt = blockSize;
while(blkCnt > 0u)
{
/* Perform Multiply-Accumulate */
*pOut++ += *px++ * coeff;
/* Decrement the loop counter */
blkCnt--;
}
/* Load the coefficient value and
* increment the coefficient buffer for the next set of state values */
coeff = *pCoeffs++;
/* Read Index, from where the state buffer should be read, is calculated. */
readIndex =
((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;
/* Wraparound of readIndex */
if(readIndex < 0)
{
readIndex += (int32_t) delaySize;
}
/* Decrement the tap loop counter */
tapCnt--;
}
#endif /* #ifndef ARM_MATH_CM0 */
}
/**
* @} end of FIR_Sparse group
*/