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# arm_fir_sparse_q15.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_q15.c
    00009 *
    00010 * Description:  Q15 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
    00057 void arm_fir_sparse_q15(
    00058   arm_fir_sparse_instance_q15 * S,
    00059   q15_t * pSrc,
    00060   q15_t * pDst,
    00061   q15_t * pScratchIn,
    00062   q31_t * pScratchOut,
    00063   uint32_t blockSize)
    00064 {
    00065
    00066   q15_t *pState = S->pState;                     /* State pointer */
    00067   q15_t *pIn = (q15_t *) pSrc;                   /* Working pointer for input */
    00068   q15_t *pOut = pDst;                            /* Working pointer for output */
    00069   q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
    00070   q15_t *px;                                     /* Temporary pointers for scratch buffer */
    00071   q15_t *pb = pScratchIn;                        /* Temporary pointers for scratch buffer */
    00072   q15_t *py = pState;                            /* Temporary pointers for state buffer */
    00073   int32_t *pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
    00074   uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
    00075   uint16_t numTaps = S->numTaps;                 /* Filter order */
    00076   int32_t readIndex;                             /* Read index of the state buffer */
    00077   uint32_t tapCnt, blkCnt;                       /* loop counters */
    00078   q15_t coeff = *pCoeffs++;                      /* Read the first coefficient value */
    00079   q31_t *pScr2 = pScratchOut;                    /* Working pointer for pScratchOut */
    00080   q31_t in1, in2;                                /* Temporary variables */
    00081
    00082
    00083
    00084   /* BlockSize of Input samples are copied into the state buffer */
    00085   /* StateIndex points to the starting position to write in the state buffer */
    00086   arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);
    00087
    00088   /* Loop over the number of taps. */
    00089   tapCnt = numTaps;
    00090
    00091   /* Read Index, from where the state buffer should be read, is calculated. */
    00092   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
    00093
    00094   /* Wraparound of readIndex */
    00095   if(readIndex < 0)
    00096   {
    00097     readIndex += (int32_t) delaySize;
    00098   }
    00099
    00100   /* Working pointer for state buffer is updated */
    00101   py = pState;
    00102
    00103   /* blockSize samples are read from the state buffer */
    00104   arm_circularRead_q15(py, delaySize, &readIndex, 1,
    00105                        pb, pb, blockSize, 1, blockSize);
    00106
    00107   /* Working pointer for the scratch buffer of state values */
    00108   px = pb;
    00109
    00110   /* Working pointer for scratch buffer of output values */
    00111   pScratchOut = pScr2;
    00112
    00113   /* Loop over the blockSize. Unroll by a factor of 4.
    00114    * Compute 4 multiplications at a time. */
    00115   blkCnt = blockSize >> 2;
    00116
    00117   while(blkCnt > 0u)
    00118   {
    00119     /* Perform multiplication and store in the scratch buffer */
    00120     *pScratchOut++ = ((q31_t) * px++ * coeff);
    00121     *pScratchOut++ = ((q31_t) * px++ * coeff);
    00122     *pScratchOut++ = ((q31_t) * px++ * coeff);
    00123     *pScratchOut++ = ((q31_t) * px++ * coeff);
    00124
    00125     /* Decrement the loop counter */
    00126     blkCnt--;
    00127   }
    00128
    00129   /* If the blockSize is not a multiple of 4,
    00130    * compute the remaining samples */
    00131   blkCnt = blockSize % 0x4u;
    00132
    00133   while(blkCnt > 0u)
    00134   {
    00135     /* Perform multiplication and store in the scratch buffer */
    00136     *pScratchOut++ = ((q31_t) * px++ * coeff);
    00137
    00138     /* Decrement the loop counter */
    00139     blkCnt--;
    00140   }
    00141
    00142   /* Load the coefficient value and
    00143    * increment the coefficient buffer for the next set of state values */
    00144   coeff = *pCoeffs++;
    00145
    00146   /* Read Index, from where the state buffer should be read, is calculated. */
    00147   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
    00148
    00149   /* Wraparound of readIndex */
    00150   if(readIndex < 0)
    00151   {
    00152     readIndex += (int32_t) delaySize;
    00153   }
    00154
    00155   /* Loop over the number of taps. */
    00156   tapCnt = (uint32_t) numTaps - 1u;
    00157
    00158   while(tapCnt > 0u)
    00159   {
    00160     /* Working pointer for state buffer is updated */
    00161     py = pState;
    00162
    00163     /* blockSize samples are read from the state buffer */
    00164     arm_circularRead_q15(py, delaySize, &readIndex, 1,
    00165                          pb, pb, blockSize, 1, blockSize);
    00166
    00167     /* Working pointer for the scratch buffer of state values */
    00168     px = pb;
    00169
    00170     /* Working pointer for scratch buffer of output values */
    00171     pScratchOut = pScr2;
    00172
    00173     /* Loop over the blockSize. Unroll by a factor of 4.
    00174      * Compute 4 MACS at a time. */
    00175     blkCnt = blockSize >> 2;
    00176
    00177     while(blkCnt > 0u)
    00178     {
    00179       /* Perform Multiply-Accumulate */
    00180       *pScratchOut++ += (q31_t) * px++ * coeff;
    00181       *pScratchOut++ += (q31_t) * px++ * coeff;
    00182       *pScratchOut++ += (q31_t) * px++ * coeff;
    00183       *pScratchOut++ += (q31_t) * px++ * coeff;
    00184
    00185       /* Decrement the loop counter */
    00186       blkCnt--;
    00187     }
    00188
    00189     /* If the blockSize is not a multiple of 4,
    00190      * compute the remaining samples */
    00191     blkCnt = blockSize % 0x4u;
    00192
    00193     while(blkCnt > 0u)
    00194     {
    00195       /* Perform Multiply-Accumulate */
    00196       *pScratchOut++ += (q31_t) * px++ * coeff;
    00197
    00198       /* Decrement the loop counter */
    00199       blkCnt--;
    00200     }
    00201
    00202     /* Load the coefficient value and
    00203      * increment the coefficient buffer for the next set of state values */
    00204     coeff = *pCoeffs++;
    00205
    00206     /* Read Index, from where the state buffer should be read, is calculated. */
    00207     readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
    00208
    00209     /* Wraparound of readIndex */
    00210     if(readIndex < 0)
    00211     {
    00212       readIndex += (int32_t) delaySize;
    00213     }
    00214
    00215     /* Decrement the tap loop counter */
    00216     tapCnt--;
    00217   }
    00218
    00219   /* All the output values are in pScratchOut buffer.
    00220      Convert them into 1.15 format, saturate and store in the destination buffer. */
    00221   /* Loop over the blockSize. */
    00222   blkCnt = blockSize >> 2;
    00223
    00224   while(blkCnt > 0u)
    00225   {
    00226     in1 = *pScr2++;
    00227     in2 = *pScr2++;
    00228     *__SIMD32(pOut)++ =
    00229       __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
    00230               16);
    00231
    00232     in1 = *pScr2++;
    00233     in2 = *pScr2++;
    00234     *__SIMD32(pOut)++ =
    00235       __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
    00236               16);
    00237
    00238     blkCnt--;
    00239
    00240   }
    00241
    00242   /* If the blockSize is not a multiple of 4,
    00243      remaining samples are processed in the below loop */
    00244   blkCnt = blockSize % 0x4u;
    00245
    00246   while(blkCnt > 0u)
    00247   {
    00248     *pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
    00249     blkCnt--;
    00250   }
    00251 }
    00252

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