arm_fir_sparse_q15.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        19. March 2015
00005 * $Revision:    V.1.4.5
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 - 2u;
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     /* Compute last tap without the final read of pTapDelay */      
00236 
00237     /* Working pointer for state buffer is updated */
00238     py = pState;
00239 
00240     /* blockSize samples are read from the state buffer */
00241     arm_circularRead_q15(py, delaySize, &readIndex, 1,
00242                                              pb, pb, blockSize, 1, blockSize);
00243 
00244     /* Working pointer for the scratch buffer of state values */
00245     px = pb;
00246 
00247     /* Working pointer for scratch buffer of output values */
00248     pScratchOut = pScr2;
00249 
00250     /* Loop over the blockSize. Unroll by a factor of 4.    
00251      * Compute 4 MACS at a time. */
00252     blkCnt = blockSize >> 2;
00253 
00254     while(blkCnt > 0u)
00255     {
00256         /* Perform Multiply-Accumulate */
00257         *pScratchOut++ += (q31_t) * px++ * coeff;
00258         *pScratchOut++ += (q31_t) * px++ * coeff;
00259         *pScratchOut++ += (q31_t) * px++ * coeff;
00260         *pScratchOut++ += (q31_t) * px++ * coeff;
00261 
00262         /* Decrement the loop counter */
00263         blkCnt--;
00264     }
00265 
00266     /* If the blockSize is not a multiple of 4,    
00267      * compute the remaining samples */
00268     blkCnt = blockSize % 0x4u;
00269 
00270     while(blkCnt > 0u)
00271     {
00272         /* Perform Multiply-Accumulate */
00273         *pScratchOut++ += (q31_t) * px++ * coeff;
00274 
00275         /* Decrement the loop counter */
00276         blkCnt--;
00277     }
00278 
00279   /* All the output values are in pScratchOut buffer.    
00280      Convert them into 1.15 format, saturate and store in the destination buffer. */
00281   /* Loop over the blockSize. */
00282   blkCnt = blockSize >> 2;
00283 
00284   while(blkCnt > 0u)
00285   {
00286     in1 = *pScr2++;
00287     in2 = *pScr2++;
00288 
00289 #ifndef  ARM_MATH_BIG_ENDIAN
00290 
00291     *__SIMD32(pOut)++ =
00292       __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
00293               16);
00294 
00295 #else
00296     *__SIMD32(pOut)++ =
00297       __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
00298               16);
00299 
00300 #endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
00301 
00302     in1 = *pScr2++;
00303 
00304     in2 = *pScr2++;
00305 
00306 #ifndef  ARM_MATH_BIG_ENDIAN
00307 
00308     *__SIMD32(pOut)++ =
00309       __PKHBT((q15_t) __SSAT(in1 >> 15, 16), (q15_t) __SSAT(in2 >> 15, 16),
00310               16);
00311 
00312 #else
00313 
00314     *__SIMD32(pOut)++ =
00315       __PKHBT((q15_t) __SSAT(in2 >> 15, 16), (q15_t) __SSAT(in1 >> 15, 16),
00316               16);
00317 
00318 #endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */
00319 
00320 
00321     blkCnt--;
00322 
00323   }
00324 
00325   /* If the blockSize is not a multiple of 4,    
00326      remaining samples are processed in the below loop */
00327   blkCnt = blockSize % 0x4u;
00328 
00329   while(blkCnt > 0u)
00330   {
00331     *pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
00332     blkCnt--;
00333   }
00334 
00335 #else
00336 
00337   /* Run the below code for Cortex-M0 */
00338 
00339   /* BlockSize of Input samples are copied into the state buffer */
00340   /* StateIndex points to the starting position to write in the state buffer */
00341   arm_circularWrite_q15(py, delaySize, &S->stateIndex, 1, pIn, 1, blockSize);
00342 
00343   /* Loop over the number of taps. */
00344   tapCnt = numTaps;
00345 
00346   /* Read Index, from where the state buffer should be read, is calculated. */
00347   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00348 
00349   /* Wraparound of readIndex */
00350   if(readIndex < 0)
00351   {
00352     readIndex += (int32_t) delaySize;
00353   }
00354 
00355   /* Working pointer for state buffer is updated */
00356   py = pState;
00357 
00358   /* blockSize samples are read from the state buffer */
00359   arm_circularRead_q15(py, delaySize, &readIndex, 1,
00360                        pb, pb, blockSize, 1, blockSize);
00361 
00362   /* Working pointer for the scratch buffer of state values */
00363   px = pb;
00364 
00365   /* Working pointer for scratch buffer of output values */
00366   pScratchOut = pScr2;
00367 
00368   blkCnt = blockSize;
00369 
00370   while(blkCnt > 0u)
00371   {
00372     /* Perform multiplication and store in the scratch buffer */
00373     *pScratchOut++ = ((q31_t) * px++ * coeff);
00374 
00375     /* Decrement the loop counter */
00376     blkCnt--;
00377   }
00378 
00379   /* Load the coefficient value and           
00380    * increment the coefficient buffer for the next set of state values */
00381   coeff = *pCoeffs++;
00382 
00383   /* Read Index, from where the state buffer should be read, is calculated. */
00384   readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00385 
00386   /* Wraparound of readIndex */
00387   if(readIndex < 0)
00388   {
00389     readIndex += (int32_t) delaySize;
00390   }
00391 
00392   /* Loop over the number of taps. */
00393   tapCnt = (uint32_t) numTaps - 2u;
00394 
00395   while(tapCnt > 0u)
00396   {
00397     /* Working pointer for state buffer is updated */
00398     py = pState;
00399 
00400     /* blockSize samples are read from the state buffer */
00401     arm_circularRead_q15(py, delaySize, &readIndex, 1,
00402                          pb, pb, blockSize, 1, blockSize);
00403 
00404     /* Working pointer for the scratch buffer of state values */
00405     px = pb;
00406 
00407     /* Working pointer for scratch buffer of output values */
00408     pScratchOut = pScr2;
00409 
00410     blkCnt = blockSize;
00411 
00412     while(blkCnt > 0u)
00413     {
00414       /* Perform Multiply-Accumulate */
00415       *pScratchOut++ += (q31_t) * px++ * coeff;
00416 
00417       /* Decrement the loop counter */
00418       blkCnt--;
00419     }
00420 
00421     /* Load the coefficient value and           
00422      * increment the coefficient buffer for the next set of state values */
00423     coeff = *pCoeffs++;
00424 
00425     /* Read Index, from where the state buffer should be read, is calculated. */
00426     readIndex = (S->stateIndex - blockSize) - *pTapDelay++;
00427 
00428     /* Wraparound of readIndex */
00429     if(readIndex < 0)
00430     {
00431       readIndex += (int32_t) delaySize;
00432     }
00433 
00434     /* Decrement the tap loop counter */
00435     tapCnt--;
00436   }
00437     
00438     /* Compute last tap without the final read of pTapDelay */  
00439     
00440     /* Working pointer for state buffer is updated */
00441     py = pState;
00442 
00443     /* blockSize samples are read from the state buffer */
00444     arm_circularRead_q15(py, delaySize, &readIndex, 1,
00445                                              pb, pb, blockSize, 1, blockSize);
00446 
00447     /* Working pointer for the scratch buffer of state values */
00448     px = pb;
00449 
00450     /* Working pointer for scratch buffer of output values */
00451     pScratchOut = pScr2;
00452 
00453     blkCnt = blockSize;
00454 
00455     while(blkCnt > 0u)
00456     {
00457         /* Perform Multiply-Accumulate */
00458         *pScratchOut++ += (q31_t) * px++ * coeff;
00459 
00460         /* Decrement the loop counter */
00461         blkCnt--;
00462     }
00463 
00464   /* All the output values are in pScratchOut buffer.       
00465      Convert them into 1.15 format, saturate and store in the destination buffer. */
00466   /* Loop over the blockSize. */
00467   blkCnt = blockSize;
00468 
00469   while(blkCnt > 0u)
00470   {
00471     *pOut++ = (q15_t) __SSAT(*pScr2++ >> 15, 16);
00472     blkCnt--;
00473   }
00474 
00475 #endif /*   #ifndef ARM_MATH_CM0_FAMILY */
00476 
00477 }
00478 
00479 /**    
00480  * @} end of FIR_Sparse group    
00481  */