##// END OF EJS Templates
HG_REPOSITORIES » LPP » INSTRUMENTATION » libuc2
RSS

Clone from http://pc-instru.lpp.polytechnique.fr:5000/libuc2

Removed error on fat32 library, seems now to be able navigate among sectors in...
Removed error on fat32 library, seems now to be able navigate among sectors in both directions. Improved SDLCD drawing performances by almost 1000x.
jeandet@pc-de-jeandet3.LAB-LPP.LOCAL - - Load All Authors

File last commit:

r41:27c5438a4566 dev_alexis
r68:104125d87b89 dev_alexis
Show More
arm_fir_decimate_fast_q31.c
220 lines | 6.8 KiB | text/x-c | CLexer
/ lib / src / stm32f4 / CPU / CMSIS / DSP_Lib / Source / FilteringFunctions / arm_fir_decimate_fast_q31.c
History | Annotation | Raw |Copy content |Copy permalink
/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date: 15. July 2011
* $Revision: V1.0.10
*
* Project: CMSIS DSP Library
* Title: arm_fir_decimate_fast_q31.c
*
* Description: Fast Q31 FIR Decimator.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* 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.
* -------------------------------------------------------------------- */
#include "arm_math.h"
/**
* @ingroup groupFilters
*/
/**
* @addtogroup FIR_decimate
* @{
*/
/**
* @brief Processing function for the Q31 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4.
* @param[in] *S points to an instance of the Q31 FIR decimator 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 input samples to process per call.
* @return none
*
* <b>Scaling and Overflow Behavior:</b>
*
* \par
* This function is optimized for speed at the expense of fixed-point precision and overflow protection.
* The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
* These intermediate results are added to a 2.30 accumulator.
* Finally, the accumulator is saturated and converted to a 1.31 result.
* The fast version has the same overflow behavior as the standard version and provides less precision since it discards the low 32 bits of each multiplication result.
* In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits (where log2 is read as log to the base 2).
*
* \par
* Refer to the function <code>arm_fir_decimate_q31()</code> for a slower implementation of this function which uses a 64-bit accumulator to provide higher precision.
* Both the slow and the fast versions use the same instance structure.
* Use the function <code>arm_fir_decimate_init_q31()</code> to initialize the filter structure.
*/
void arm_fir_decimate_fast_q31(
arm_fir_decimate_instance_q31 * S,
q31_t * pSrc,
q31_t * pDst,
uint32_t blockSize)
{
q31_t *pState = S->pState; /* State pointer */
q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
q31_t *pStateCurnt; /* Points to the current sample of the state */
q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
q31_t *px; /* Temporary pointers for state buffer */
q31_t *pb; /* Temporary pointers for coefficient buffer */
q63_t sum0; /* Accumulator */
uint32_t numTaps = S->numTaps; /* Number of taps */
uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */
/* S->pState buffer contains previous frame (numTaps - 1) samples */
/* pStateCurnt points to the location where the new input data should be written */
pStateCurnt = S->pState + (numTaps - 1u);
/* Total number of output samples to be computed */
blkCnt = outBlockSize;
while(blkCnt > 0u)
{
/* Copy decimation factor number of new input samples into the state buffer */
i = S->M;
do
{
*pStateCurnt++ = *pSrc++;
} while(--i);
/* Set accumulator to zero */
sum0 = 0;
/* Initialize state pointer */
px = pState;
/* Initialize coeff pointer */
pb = pCoeffs;
/* Loop unrolling. Process 4 taps at a time. */
tapCnt = numTaps >> 2;
/* 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-1] sample */
x0 = *(px++);
/* Perform the multiply-accumulate */
sum0 = (q31_t) ((((q63_t) x0 * c0) + (sum0 << 32)) >> 32);
/* Read the b[numTaps-2] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-2] sample */
x0 = *(px++);
/* Perform the multiply-accumulate */
sum0 = (q31_t) ((((q63_t) x0 * c0) + (sum0 << 32)) >> 32);
/* Read the b[numTaps-3] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-3] sample */
x0 = *(px++);
/* Perform the multiply-accumulate */
sum0 = (q31_t) ((((q63_t) x0 * c0) + (sum0 << 32)) >> 32);
/* Read the b[numTaps-4] coefficient */
c0 = *(pb++);
/* Read x[n-numTaps-4] sample */
x0 = *(px++);
/* Perform the multiply-accumulate */
sum0 = (q31_t) ((((q63_t) x0 * c0) + (sum0 << 32)) >> 32);
/* Decrement the loop counter */
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 */
x0 = *(px++);
/* Perform the multiply-accumulate */
sum0 = (q31_t) ((((q63_t) x0 * c0) + (sum0 << 32)) >> 32);
/* Decrement the loop counter */
tapCnt--;
}
/* Advance the state pointer by the decimation factor
* to process the next group of decimation factor number samples */
pState = pState + S->M;
/* The result is in the accumulator, store in the destination buffer. */
*pDst++ = (q31_t) (sum0 << 1);
/* Decrement the loop counter */
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;
i = (numTaps - 1u) >> 2u;
/* copy data */
while(i > 0u)
{
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
i--;
}
i = (numTaps - 1u) % 0x04u;
/* copy data */
while(i > 0u)
{
*pStateCurnt++ = *pState++;
/* Decrement the loop counter */
i--;
}
}
/**
* @} end of FIR_decimate group
*/