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# arm_fir_sparse_q31.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_fir_sparse_q31.c
    00009 *
    00010 * Description:  Q31 sparse FIR filter processing function.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated
    00025 *
    00026 * Version 0.0.7  2010/06/10
    00027 *    Misra-C changes done
    00028 * ------------------------------------------------------------------- */
    00029 #include "arm_math.h"
    00030
    00031
    00055 void arm_fir_sparse_q31(
    00056   arm_fir_sparse_instance_q31 * S,
    00057   q31_t * pSrc,
    00058   q31_t * pDst,
    00059   q31_t * pScratchIn,
    00060   uint32_t blockSize)
    00061 {
    00062
    00063   q31_t *pState = S->pState;                     /* State pointer */
    00064   q31_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    00065   q31_t *px;                                     /* Scratch buffer pointer */
    00066   q31_t *py = pState;                            /* Temporary pointers for state buffer */
    00067   q31_t *pb = pScratchIn;                        /* Temporary pointers for scratch buffer */
    00068   q31_t *pOut;                                   /* Destination pointer */
    00069   q63_t out;                                     /* Temporary output variable */
    00070   int32_t *pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
    00071   uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
    00072   uint16_t numTaps = S->numTaps;                 /* Filter order */
    00073   int32_t readIndex;                             /* Read index of the state buffer */
    00074   uint32_t tapCnt, blkCnt;                       /* loop counters */
    00075   q31_t coeff = *pCoeffs++;                      /* Read the first coefficient value */
    00076   q31_t in;
    00077
    00078
    00079   /* BlockSize of Input samples are copied into the state buffer */
    00080   /* StateIndex points to the starting position to write in the state buffer */
    00081   arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1,
    00082                         (int32_t *) pSrc, 1, blockSize);
    00083
    00084   /* Read Index, from where the state buffer should be read, is calculated. */
    00085   readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
    00086
    00087   /* Wraparound of readIndex */
    00088   if(readIndex < 0)
    00089   {
    00090     readIndex += (int32_t) delaySize;
    00091   }
    00092
    00093   /* Working pointer for state buffer is updated */
    00094   py = pState;
    00095
    00096   /* blockSize samples are read from the state buffer */
    00097   arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
    00098                        (int32_t *) pb, (int32_t *) pb, blockSize, 1,
    00099                        blockSize);
    00100
    00101   /* Working pointer for the scratch buffer of state values */
    00102   px = pb;
    00103
    00104   /* Working pointer for scratch buffer of output values */
    00105   pOut = pDst;
    00106
    00107   /* Loop over the blockSize. Unroll by a factor of 4.
    00108    * Compute 4 Multiplications at a time. */
    00109   blkCnt = blockSize >> 2;
    00110
    00111   while(blkCnt > 0u)
    00112   {
    00113     /* Perform Multiplications and store in the destination buffer */
    00114     *pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
    00115     *pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
    00116     *pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
    00117     *pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
    00118
    00119     /* Decrement the loop counter */
    00120     blkCnt--;
    00121   }
    00122
    00123   /* If the blockSize is not a multiple of 4,
    00124    * compute the remaining samples */
    00125   blkCnt = blockSize % 0x4u;
    00126
    00127   while(blkCnt > 0u)
    00128   {
    00129     /* Perform Multiplications and store in the destination buffer */
    00130     *pOut++ = (q31_t) (((q63_t) * px++ * coeff) >> 32);
    00131
    00132     /* Decrement the loop counter */
    00133     blkCnt--;
    00134   }
    00135
    00136   /* Load the coefficient value and
    00137    * increment the coefficient buffer for the next set of state values */
    00138   coeff = *pCoeffs++;
    00139
    00140   /* Read Index, from where the state buffer should be read, is calculated. */
    00141   readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
    00142
    00143   /* Wraparound of readIndex */
    00144   if(readIndex < 0)
    00145   {
    00146     readIndex += (int32_t) delaySize;
    00147   }
    00148
    00149   /* Loop over the number of taps. */
    00150   tapCnt = (uint32_t) numTaps - 1u;
    00151
    00152   while(tapCnt > 0u)
    00153   {
    00154     /* Working pointer for state buffer is updated */
    00155     py = pState;
    00156
    00157     /* blockSize samples are read from the state buffer */
    00158     arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
    00159                          (int32_t *) pb, (int32_t *) pb, blockSize, 1,
    00160                          blockSize);
    00161
    00162     /* Working pointer for the scratch buffer of state values */
    00163     px = pb;
    00164
    00165     /* Working pointer for scratch buffer of output values */
    00166     pOut = pDst;
    00167
    00168     /* Loop over the blockSize. Unroll by a factor of 4.
    00169      * Compute 4 MACS at a time. */
    00170     blkCnt = blockSize >> 2;
    00171
    00172     while(blkCnt > 0u)
    00173     {
    00174       out = *pOut;
    00175       out += ((q63_t) * px++ * coeff) >> 32;
    00176       *pOut++ = (q31_t) (out);
    00177
    00178       out = *pOut;
    00179       out += ((q63_t) * px++ * coeff) >> 32;
    00180       *pOut++ = (q31_t) (out);
    00181
    00182       out = *pOut;
    00183       out += ((q63_t) * px++ * coeff) >> 32;
    00184       *pOut++ = (q31_t) (out);
    00185
    00186       out = *pOut;
    00187       out += ((q63_t) * px++ * coeff) >> 32;
    00188       *pOut++ = (q31_t) (out);
    00189
    00190       /* Decrement the loop counter */
    00191       blkCnt--;
    00192     }
    00193
    00194     /* If the blockSize is not a multiple of 4,
    00195      * compute the remaining samples */
    00196     blkCnt = blockSize % 0x4u;
    00197
    00198     while(blkCnt > 0u)
    00199     {
    00200       /* Perform Multiply-Accumulate */
    00201       out = *pOut;
    00202       out += ((q63_t) * px++ * coeff) >> 32;
    00203       *pOut++ = (q31_t) (out);
    00204
    00205       /* Decrement the loop counter */
    00206       blkCnt--;
    00207     }
    00208
    00209     /* Load the coefficient value and
    00210      * increment the coefficient buffer for the next set of state values */
    00211     coeff = *pCoeffs++;
    00212
    00213     /* Read Index, from where the state buffer should be read, is calculated. */
    00214     readIndex = (int32_t) (S->stateIndex - blockSize) - *pTapDelay++;
    00215
    00216     /* Wraparound of readIndex */
    00217     if(readIndex < 0)
    00218     {
    00219       readIndex += (int32_t) delaySize;
    00220     }
    00221
    00222     /* Decrement the tap loop counter */
    00223     tapCnt--;
    00224   }
    00225
    00226   /* Working output pointer is updated */
    00227   pOut = pDst;
    00228
    00229   /* Output is converted into 1.15 format. */
    00230   /* Loop over the blockSize. Unroll by a factor of 4.
    00231    * process 4 output samples at a time. */
    00232   blkCnt = blockSize >> 2;
    00233
    00234   while(blkCnt > 0u)
    00235   {
    00236     in = *pOut << 1;
    00237     *pOut++ = in;
    00238     in = *pOut << 1;
    00239     *pOut++ = in;
    00240     in = *pOut << 1;
    00241     *pOut++ = in;
    00242     in = *pOut << 1;
    00243     *pOut++ = in;
    00244
    00245     /* Decrement the loop counter */
    00246     blkCnt--;
    00247   }
    00248
    00249   /* If the blockSize is not a multiple of 4,
    00250    * process the remaining output samples */
    00251   blkCnt = blockSize % 0x4u;
    00252
    00253   while(blkCnt > 0u)
    00254   {
    00255     in = *pOut << 1;
    00256     *pOut++ = in;
    00257
    00258     /* Decrement the loop counter */
    00259     blkCnt--;
    00260   }
    00261 }
    00262

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