arm_fir_sparse_q15.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        17. January 2013
00005 * $Revision:    V1.4.1
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/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.    
00039 * ------------------------------------------------------------------- */
00040 #include "arm_math.h"
00041 
00042 /**    
00043  * @addtogroup FIR_Sparse    
00044  * @{    
00045  */
00046 
00047 /**   
00048  * @brief Processing function for the Q15 sparse FIR filter.   
00049  * @param[in]  *S           points to an instance of the Q15 sparse FIR structure.   
00050  * @param[in]  *pSrc        points to the block of input data.   
00051  * @param[out] *pDst        points to the block of output data   
00052  * @param[in]  *pScratchIn  points to a temporary buffer of size blockSize.   
00053  * @param[in]  *pScratchOut points to a temporary buffer of size blockSize.   
00054  * @param[in]  blockSize    number of input samples to process per call.   
00055  * @return none.   
00056  *    
00057  * <b>Scaling and Overflow Behavior:</b>    
00058  * \par    
00059  * The function is implemented using an internal 32-bit accumulator.   
00060  * The 1.15 x 1.15 multiplications yield a 2.30 result and these are added to a 2.30 accumulator.   
00061  * Thus the full precision of the multiplications is maintained but there is only a single guard bit in the accumulator.   
00062  * If the accumulator result overflows it will wrap around rather than saturate.   
00063  * After all multiply-accumulates are performed, the 2.30 accumulator is truncated to 2.15 format and then saturated to 1.15 format.    
00064  * In order to avoid overflows the input signal or coefficients must be scaled down by log2(numTaps) bits.   
00065  */
00066 
00067 
00068 void arm_fir_sparse_q15(
00069   arm_fir_sparse_instance_q15 * S,
00070   q15_t * pSrc,
00071   q15_t * pDst,
00072   q15_t * pScratchIn,
00073   q31_t * pScratchOut,
00074   uint32_t blockSize)
00075 {
00076 
00077   q15_t *pState = S->pState;                     /* State pointer */
00078   q15_t *pIn = pSrc;                             /* Working pointer for input */
00079   q15_t *pOut = pDst;                            /* Working pointer for output */
00080   q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
00081   q15_t *px;                                     /* Temporary pointers for scratch buffer */
00082   q15_t *pb = pScratchIn;                        /* Temporary pointers for scratch buffer */
00083   q15_t *py = pState;                            /* Temporary pointers for state buffer */
00084   int32_t *pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
00085   uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
00086   uint16_t numTaps = S->numTaps;                 /* Filter order */
00087   int32_t readIndex;                             /* Read index of the state buffer */
00088   uint32_t tapCnt, blkCnt;                       /* loop counters */
00089   q15_t coeff = *pCoeffs++;                      /* Read the first coefficient value */
00090   q31_t *pScr2 = pScratchOut;                    /* Working pointer for pScratchOut */
00091 
00092 
00093 #ifndef ARM_MATH_CM0_FAMILY
00094 
00095   /* Run the below code for Cortex-M4 and Cortex-M3 */
00096 
00097   q31_t in1, in2;                                /* Temporary variables */
00098 
00099 
00100   /* BlockSize of Input samples are copied into the state buffer */
00101   /* StateIndex points to the starting position to write in the state buffer */
00102   arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);
00103 
00104   /* Loop over the number of taps. */
00105   tapCnt = numTaps;
00106 
00107   /* Read Index, from where the state buffer should be read, is calculated. */
00108   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00109 
00110   /* Wraparound of readIndex */
00111   if(readIndex < 0)
00112   {
00113     readIndex += (int32_t) delaySize;
00114   }
00115 
00116   /* Working pointer for state buffer is updated */
00117   py = pState;
00118 
00119   /* blockSize samples are read from the state buffer */
00120   arm_circularRead_q15(py, delaySize, &readIndex, 1,
00121                        pb, pb, blockSize, 1, blockSize);
00122 
00123   /* Working pointer for the scratch buffer of state values */
00124   px = pb;
00125 
00126   /* Working pointer for scratch buffer of output values */
00127   pScratchOut = pScr2;
00128 
00129   /* Loop over the blockSize. Unroll by a factor of 4.    
00130    * Compute 4 multiplications at a time. */
00131   blkCnt = blockSize >> 2;
00132 
00133   while(blkCnt > 0u)
00134   {
00135     /* Perform multiplication and store in the scratch buffer */
00136     *pScratchOut++ = ((q31_t) * px++ * coeff);
00137     *pScratchOut++ = ((q31_t) * px++ * coeff);
00138     *pScratchOut++ = ((q31_t) * px++ * coeff);
00139     *pScratchOut++ = ((q31_t) * px++ * coeff);
00140 
00141     /* Decrement the loop counter */
00142     blkCnt--;
00143   }
00144 
00145   /* If the blockSize is not a multiple of 4,    
00146    * compute the remaining samples */
00147   blkCnt = blockSize % 0x4u;
00148 
00149   while(blkCnt > 0u)
00150   {
00151     /* Perform multiplication and store in the scratch buffer */
00152     *pScratchOut++ = ((q31_t) * px++ * coeff);
00153 
00154     /* Decrement the loop counter */
00155     blkCnt--;
00156   }
00157 
00158   /* Load the coefficient value and    
00159    * increment the coefficient buffer for the next set of state values */
00160   coeff = *pCoeffs++;
00161 
00162   /* Read Index, from where the state buffer should be read, is calculated. */
00163   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00164 
00165   /* Wraparound of readIndex */
00166   if(readIndex < 0)
00167   {
00168     readIndex += (int32_t) delaySize;
00169   }
00170 
00171   /* Loop over the number of taps. */
00172   tapCnt = (uint32_t) numTaps - 1u;
00173 
00174   while(tapCnt > 0u)
00175   {
00176     /* Working pointer for state buffer is updated */
00177     py = pState;
00178 
00179     /* blockSize samples are read from the state buffer */
00180     arm_circularRead_q15(py, delaySize, &readIndex, 1,
00181                          pb, pb, blockSize, 1, blockSize);
00182 
00183     /* Working pointer for the scratch buffer of state values */
00184     px = pb;
00185 
00186     /* Working pointer for scratch buffer of output values */
00187     pScratchOut = pScr2;
00188 
00189     /* Loop over the blockSize. Unroll by a factor of 4.    
00190      * Compute 4 MACS at a time. */
00191     blkCnt = blockSize >> 2;
00192 
00193     while(blkCnt > 0u)
00194     {
00195       /* Perform Multiply-Accumulate */
00196       *pScratchOut++ += (q31_t) * px++ * coeff;
00197       *pScratchOut++ += (q31_t) * px++ * coeff;
00198       *pScratchOut++ += (q31_t) * px++ * coeff;
00199       *pScratchOut++ += (q31_t) * px++ * coeff;
00200 
00201       /* Decrement the loop counter */
00202       blkCnt--;
00203     }
00204 
00205     /* If the blockSize is not a multiple of 4,    
00206      * compute the remaining samples */
00207     blkCnt = blockSize % 0x4u;
00208 
00209     while(blkCnt > 0u)
00210     {
00211       /* Perform Multiply-Accumulate */
00212       *pScratchOut++ += (q31_t) * px++ * coeff;
00213 
00214       /* Decrement the loop counter */
00215       blkCnt--;
00216     }
00217 
00218     /* Load the coefficient value and    
00219      * increment the coefficient buffer for the next set of state values */
00220     coeff = *pCoeffs++;
00221 
00222     /* Read Index, from where the state buffer should be read, is calculated. */
00223     readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00224 
00225     /* Wraparound of readIndex */
00226     if(readIndex < 0)
00227     {
00228       readIndex += (int32_t) delaySize;
00229     }
00230 
00231     /* Decrement the tap loop counter */
00232     tapCnt--;
00233   }
00234 
00235   /* All the output values are in pScratchOut buffer.    
00236      Convert them into 1.15 format, saturate and store in the destination buffer. */
00237   /* Loop over the blockSize. */
00238   blkCnt = blockSize >> 2;
00239 
00240   while(blkCnt > 0u)
00241   {
00242     in1 = *pScr2++;
00243     in2 = *pScr2++;
00244 
00245 #ifndef  ARM_MATH_BIG_ENDIAN
00246 
00247     *__SIMD32(pOut)++ =
00248       __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
00249               16);
00250 
00251 #else
00252     *__SIMD32(pOut)++ =
00253       __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
00254               16);
00255 
00256 #endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
00257 
00258     in1 = *pScr2++;
00259 
00260     in2 = *pScr2++;
00261 
00262 #ifndef  ARM_MATH_BIG_ENDIAN
00263 
00264     *__SIMD32(pOut)++ =
00265       __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
00266               16);
00267 
00268 #else
00269 
00270     *__SIMD32(pOut)++ =
00271       __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
00272               16);
00273 
00274 #endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
00275 
00276 
00277     blkCnt--;
00278 
00279   }
00280 
00281   /* If the blockSize is not a multiple of 4,    
00282      remaining samples are processed in the below loop */
00283   blkCnt = blockSize % 0x4u;
00284 
00285   while(blkCnt > 0u)
00286   {
00287     *pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
00288     blkCnt--;
00289   }
00290 
00291 #else
00292 
00293   /* Run the below code for Cortex-M0 */
00294 
00295   /* BlockSize of Input samples are copied into the state buffer */
00296   /* StateIndex points to the starting position to write in the state buffer */
00297   arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);
00298 
00299   /* Loop over the number of taps. */
00300   tapCnt = numTaps;
00301 
00302   /* Read Index, from where the state buffer should be read, is calculated. */
00303   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00304 
00305   /* Wraparound of readIndex */
00306   if(readIndex < 0)
00307   {
00308     readIndex += (int32_t) delaySize;
00309   }
00310 
00311   /* Working pointer for state buffer is updated */
00312   py = pState;
00313 
00314   /* blockSize samples are read from the state buffer */
00315   arm_circularRead_q15(py, delaySize, &readIndex, 1,
00316                        pb, pb, blockSize, 1, blockSize);
00317 
00318   /* Working pointer for the scratch buffer of state values */
00319   px = pb;
00320 
00321   /* Working pointer for scratch buffer of output values */
00322   pScratchOut = pScr2;
00323 
00324   blkCnt = blockSize;
00325 
00326   while(blkCnt > 0u)
00327   {
00328     /* Perform multiplication and store in the scratch buffer */
00329     *pScratchOut++ = ((q31_t) * px++ * coeff);
00330 
00331     /* Decrement the loop counter */
00332     blkCnt--;
00333   }
00334 
00335   /* Load the coefficient value and           
00336    * increment the coefficient buffer for the next set of state values */
00337   coeff = *pCoeffs++;
00338 
00339   /* Read Index, from where the state buffer should be read, is calculated. */
00340   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00341 
00342   /* Wraparound of readIndex */
00343   if(readIndex < 0)
00344   {
00345     readIndex += (int32_t) delaySize;
00346   }
00347 
00348   /* Loop over the number of taps. */
00349   tapCnt = (uint32_t) numTaps - 1u;
00350 
00351   while(tapCnt > 0u)
00352   {
00353     /* Working pointer for state buffer is updated */
00354     py = pState;
00355 
00356     /* blockSize samples are read from the state buffer */
00357     arm_circularRead_q15(py, delaySize, &readIndex, 1,
00358                          pb, pb, blockSize, 1, blockSize);
00359 
00360     /* Working pointer for the scratch buffer of state values */
00361     px = pb;
00362 
00363     /* Working pointer for scratch buffer of output values */
00364     pScratchOut = pScr2;
00365 
00366     blkCnt = blockSize;
00367 
00368     while(blkCnt > 0u)
00369     {
00370       /* Perform Multiply-Accumulate */
00371       *pScratchOut++ += (q31_t) * px++ * coeff;
00372 
00373       /* Decrement the loop counter */
00374       blkCnt--;
00375     }
00376 
00377     /* Load the coefficient value and           
00378      * increment the coefficient buffer for the next set of state values */
00379     coeff = *pCoeffs++;
00380 
00381     /* Read Index, from where the state buffer should be read, is calculated. */
00382     readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00383 
00384     /* Wraparound of readIndex */
00385     if(readIndex < 0)
00386     {
00387       readIndex += (int32_t) delaySize;
00388     }
00389 
00390     /* Decrement the tap loop counter */
00391     tapCnt--;
00392   }
00393 
00394   /* All the output values are in pScratchOut buffer.       
00395      Convert them into 1.15 format, saturate and store in the destination buffer. */
00396   /* Loop over the blockSize. */
00397   blkCnt = blockSize;
00398 
00399   while(blkCnt > 0u)
00400   {
00401     *pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
00402     blkCnt--;
00403   }
00404 
00405 #endif /*   #ifndef ARM_MATH_CM0_FAMILY */
00406 
00407 }
00408 
00409 /**    
00410  * @} end of FIR_Sparse group    
00411  */