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arm_fir_sparse_q31.c
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 r16 /* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 29. November 2010
* $Revision: V1.0.3
*
* Project: CMSIS DSP Library
* Title: arm_fir_sparse_q31.c
*
* Description: Q31 sparse 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 0.0.7 2010/06/10
* Misra-C changes done
* ------------------------------------------------------------------- */
#include "arm_math.h"
/**
* @addtogroup FIR_Sparse
* @{
*/
/**
* @brief Processing function for the Q31 sparse FIR filter.
* @param[in] *S points to an instance of the Q31 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.
*
* <b>Scaling and Overflow Behavior:</b>
* \par
* The function is implemented using an internal 32-bit accumulator.
* The 1.31 x 1.31 multiplications are truncated to 2.30 format.
* This leads to loss of precision on the intermediate multiplications and provides only a single guard bit.
* If the accumulator result overflows, it wraps around rather than saturate.
* In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits.
*/
void arm_fir_sparse_q31(
arm_fir_sparse_instance_q31 * S,
q31_t * pSrc,
q31_t * pDst,
q31_t * pScratchIn,
uint32_t blockSize)
{
q31_t *pState = S->pState; /* State pointer */
q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
q31_t *px; /* Scratch buffer pointer */
q31_t *py = pState; /* Temporary pointers for state buffer */
q31_t *pb = pScratchIn; /* Temporary pointers for scratch buffer */
q31_t *pOut; /* Destination pointer */
q63_t out; /* Temporary output variable */
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; /* Filter order */
int32_t readIndex; /* Read index of the state buffer */
uint32_t tapCnt, blkCnt; /* loop counters */
q31_t coeff = *pCoeffs++; /* Read the first coefficient value */
q31_t in;
/* 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 - 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 of state values */
px = pb;
/* Working pointer for scratch buffer of output values */
pOut = pDst;
/* Loop over the blockSize. Unroll by a factor of 4.
* Compute 4 Multiplications at a time. */
blkCnt = blockSize >> 2;
while(blkCnt > 0u)
{
/* Perform Multiplications and store in the destination buffer */
*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
/* 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 the destination buffer */
*pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
/* 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 - 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 of state values */
px = pb;
/* Working pointer for scratch buffer of output values */
pOut = pDst;
/* Loop over the blockSize. Unroll by a factor of 4.
* Compute 4 MACS at a time. */
blkCnt = blockSize >> 2;
while(blkCnt > 0u)
{
out = *pOut;
out += ((q63_t) * px++ * coeff) >> 32;
*pOut++ = (q31_t) (out);
out = *pOut;
out += ((q63_t) * px++ * coeff) >> 32;
*pOut++ = (q31_t) (out);
out = *pOut;
out += ((q63_t) * px++ * coeff) >> 32;
*pOut++ = (q31_t) (out);
out = *pOut;
out += ((q63_t) * px++ * coeff) >> 32;
*pOut++ = (q31_t) (out);
/* 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 */
out = *pOut;
out += ((q63_t) * px++ * coeff) >> 32;
*pOut++ = (q31_t) (out);
/* 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 - blockSize) - *pTapDelay++;
/* Wraparound of readIndex */
if(readIndex < 0)
{
readIndex += (int32_t) delaySize;
}
/* Decrement the tap loop counter */
tapCnt--;
}
/* Working output pointer is updated */
pOut = pDst;
/* Output is converted into 1.15 format. */
/* Loop over the blockSize. Unroll by a factor of 4.
* process 4 output samples at a time. */
blkCnt = blockSize >> 2;
while(blkCnt > 0u)
{
in = *pOut << 1;
*pOut++ = in;
in = *pOut << 1;
*pOut++ = in;
in = *pOut << 1;
*pOut++ = in;
in = *pOut << 1;
*pOut++ = in;
/* Decrement the loop counter */
blkCnt--;
}
/* If the blockSize is not a multiple of 4,
* process the remaining output samples */
blkCnt = blockSize % 0x4u;
while(blkCnt > 0u)
{
in = *pOut << 1;
*pOut++ = in;
/* Decrement the loop counter */
blkCnt--;
}
}
/**
* @} end of FIR_Sparse group
*/