00001 /* ---------------------------------------------------------------------- 00002 * Copyright (C) 2010 ARM Limited. All rights reserved. 00003 * 00004 * $Date: 15. July 2011 00005 * $Revision: V1.0.10 00006 * 00007 * Project: CMSIS DSP Library 00008 * Title: arm_fir_q31.c 00009 * 00010 * Description: Q31 FIR filter processing function. 00011 * 00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 00013 * 00014 * Version 1.0.10 2011/7/15 00015 * Big Endian support added and Merged M0 and M3/M4 Source code. 00016 * 00017 * Version 1.0.3 2010/11/29 00018 * Re-organized the CMSIS folders and updated documentation. 00019 * 00020 * Version 1.0.2 2010/11/11 00021 * Documentation updated. 00022 * 00023 * Version 1.0.1 2010/10/05 00024 * Production release and review comments incorporated. 00025 * 00026 * Version 1.0.0 2010/09/20 00027 * Production release and review comments incorporated. 00028 * 00029 * Version 0.0.5 2010/04/26 00030 * incorporated review comments and updated with latest CMSIS layer 00031 * 00032 * Version 0.0.3 2010/03/10 00033 * Initial version 00034 * -------------------------------------------------------------------- */ 00035 00036 #include "arm_math.h" 00037 00067 void arm_fir_q31( 00068 const arm_fir_instance_q31 * S, 00069 q31_t * pSrc, 00070 q31_t * pDst, 00071 uint32_t blockSize) 00072 { 00073 q31_t *pState = S->pState; /* State pointer */ 00074 q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ 00075 q31_t *pStateCurnt; /* Points to the current sample of the state */ 00076 00077 00078 #ifndef ARM_MATH_CM0 00079 00080 /* Run the below code for Cortex-M4 and Cortex-M3 */ 00081 00082 q31_t x0, x1, x2, x3; /* Temporary variables to hold state */ 00083 q31_t c0; /* Temporary variable to hold coefficient value */ 00084 q31_t *px; /* Temporary pointer for state */ 00085 q31_t *pb; /* Temporary pointer for coefficient buffer */ 00086 q63_t acc0, acc1, acc2, acc3; /* Accumulators */ 00087 uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ 00088 uint32_t i, tapCnt, blkCnt; /* Loop counters */ 00089 00090 /* S->pState points to state array which contains previous frame (numTaps - 1) samples */ 00091 /* pStateCurnt points to the location where the new input data should be written */ 00092 pStateCurnt = &(S->pState[(numTaps - 1u)]); 00093 00094 /* Apply loop unrolling and compute 4 output values simultaneously. 00095 * The variables acc0 ... acc3 hold output values that are being computed: 00096 * 00097 * acc0 = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] 00098 * acc1 = b[numTaps-1] * x[n-numTaps] + b[numTaps-2] * x[n-numTaps-1] + b[numTaps-3] * x[n-numTaps-2] +...+ b[0] * x[1] 00099 * acc2 = b[numTaps-1] * x[n-numTaps+1] + b[numTaps-2] * x[n-numTaps] + b[numTaps-3] * x[n-numTaps-1] +...+ b[0] * x[2] 00100 * acc3 = b[numTaps-1] * x[n-numTaps+2] + b[numTaps-2] * x[n-numTaps+1] + b[numTaps-3] * x[n-numTaps] +...+ b[0] * x[3] 00101 */ 00102 blkCnt = blockSize >> 2; 00103 00104 /* First part of the processing with loop unrolling. Compute 4 outputs at a time. 00105 ** a second loop below computes the remaining 1 to 3 samples. */ 00106 while(blkCnt > 0u) 00107 { 00108 /* Copy four new input samples into the state buffer */ 00109 *pStateCurnt++ = *pSrc++; 00110 *pStateCurnt++ = *pSrc++; 00111 *pStateCurnt++ = *pSrc++; 00112 *pStateCurnt++ = *pSrc++; 00113 00114 /* Set all accumulators to zero */ 00115 acc0 = 0; 00116 acc1 = 0; 00117 acc2 = 0; 00118 acc3 = 0; 00119 00120 /* Initialize state pointer */ 00121 px = pState; 00122 00123 /* Initialize coefficient pointer */ 00124 pb = pCoeffs; 00125 00126 /* Read the first three samples from the state buffer: 00127 * x[n-numTaps], x[n-numTaps-1], x[n-numTaps-2] */ 00128 x0 = *(px++); 00129 x1 = *(px++); 00130 x2 = *(px++); 00131 00132 /* Loop unrolling. Process 4 taps at a time. */ 00133 tapCnt = numTaps >> 2; 00134 i = tapCnt; 00135 00136 while(i > 0u) 00137 { 00138 /* Read the b[numTaps] coefficient */ 00139 c0 = *(pb++); 00140 00141 /* Read x[n-numTaps-3] sample */ 00142 x3 = *(px++); 00143 00144 /* acc0 += b[numTaps] * x[n-numTaps] */ 00145 acc0 += ((q63_t) x0 * c0); 00146 00147 /* acc1 += b[numTaps] * x[n-numTaps-1] */ 00148 acc1 += ((q63_t) x1 * c0); 00149 00150 /* acc2 += b[numTaps] * x[n-numTaps-2] */ 00151 acc2 += ((q63_t) x2 * c0); 00152 00153 /* acc3 += b[numTaps] * x[n-numTaps-3] */ 00154 acc3 += ((q63_t) x3 * c0); 00155 00156 /* Read the b[numTaps-1] coefficient */ 00157 c0 = *(pb++); 00158 00159 /* Read x[n-numTaps-4] sample */ 00160 x0 = *(px++); 00161 00162 /* Perform the multiply-accumulates */ 00163 acc0 += ((q63_t) x1 * c0); 00164 acc1 += ((q63_t) x2 * c0); 00165 acc2 += ((q63_t) x3 * c0); 00166 acc3 += ((q63_t) x0 * c0); 00167 00168 /* Read the b[numTaps-2] coefficient */ 00169 c0 = *(pb++); 00170 00171 /* Read x[n-numTaps-5] sample */ 00172 x1 = *(px++); 00173 00174 /* Perform the multiply-accumulates */ 00175 acc0 += ((q63_t) x2 * c0); 00176 acc1 += ((q63_t) x3 * c0); 00177 acc2 += ((q63_t) x0 * c0); 00178 acc3 += ((q63_t) x1 * c0); 00179 /* Read the b[numTaps-3] coefficients */ 00180 c0 = *(pb++); 00181 00182 /* Read x[n-numTaps-6] sample */ 00183 x2 = *(px++); 00184 00185 /* Perform the multiply-accumulates */ 00186 acc0 += ((q63_t) x3 * c0); 00187 acc1 += ((q63_t) x0 * c0); 00188 acc2 += ((q63_t) x1 * c0); 00189 acc3 += ((q63_t) x2 * c0); 00190 i--; 00191 } 00192 00193 /* If the filter length is not a multiple of 4, compute the remaining filter taps */ 00194 00195 i = numTaps - (tapCnt * 4u); 00196 while(i > 0u) 00197 { 00198 /* Read coefficients */ 00199 c0 = *(pb++); 00200 00201 /* Fetch 1 state variable */ 00202 x3 = *(px++); 00203 00204 /* Perform the multiply-accumulates */ 00205 acc0 += ((q63_t) x0 * c0); 00206 acc1 += ((q63_t) x1 * c0); 00207 acc2 += ((q63_t) x2 * c0); 00208 acc3 += ((q63_t) x3 * c0); 00209 00210 /* Reuse the present sample states for next sample */ 00211 x0 = x1; 00212 x1 = x2; 00213 x2 = x3; 00214 00215 /* Decrement the loop counter */ 00216 i--; 00217 } 00218 00219 /* Advance the state pointer by 4 to process the next group of 4 samples */ 00220 pState = pState + 4; 00221 00222 /* The results in the 4 accumulators are in 2.62 format. Convert to 1.31 00223 ** Then store the 4 outputs in the destination buffer. */ 00224 *pDst++ = (q31_t) (acc0 >> 31u); 00225 *pDst++ = (q31_t) (acc1 >> 31u); 00226 *pDst++ = (q31_t) (acc2 >> 31u); 00227 *pDst++ = (q31_t) (acc3 >> 31u); 00228 00229 /* Decrement the samples loop counter */ 00230 blkCnt--; 00231 } 00232 00233 00234 /* If the blockSize is not a multiple of 4, compute any remaining output samples here. 00235 ** No loop unrolling is used. */ 00236 blkCnt = blockSize % 4u; 00237 00238 while(blkCnt > 0u) 00239 { 00240 /* Copy one sample at a time into state buffer */ 00241 *pStateCurnt++ = *pSrc++; 00242 00243 /* Set the accumulator to zero */ 00244 acc0 = 0; 00245 00246 /* Initialize state pointer */ 00247 px = pState; 00248 00249 /* Initialize Coefficient pointer */ 00250 pb = (pCoeffs); 00251 00252 i = numTaps; 00253 00254 /* Perform the multiply-accumulates */ 00255 do 00256 { 00257 acc0 += (q63_t) * (px++) * (*(pb++)); 00258 i--; 00259 } while(i > 0u); 00260 00261 /* The result is in 2.62 format. Convert to 1.31 00262 ** Then store the output in the destination buffer. */ 00263 *pDst++ = (q31_t) (acc0 >> 31u); 00264 00265 /* Advance state pointer by 1 for the next sample */ 00266 pState = pState + 1; 00267 00268 /* Decrement the samples loop counter */ 00269 blkCnt--; 00270 } 00271 00272 /* Processing is complete. 00273 ** Now copy the last numTaps - 1 samples to the satrt of the state buffer. 00274 ** This prepares the state buffer for the next function call. */ 00275 00276 /* Points to the start of the state buffer */ 00277 pStateCurnt = S->pState; 00278 00279 tapCnt = (numTaps - 1u) >> 2u; 00280 00281 /* copy data */ 00282 while(tapCnt > 0u) 00283 { 00284 *pStateCurnt++ = *pState++; 00285 *pStateCurnt++ = *pState++; 00286 *pStateCurnt++ = *pState++; 00287 *pStateCurnt++ = *pState++; 00288 00289 /* Decrement the loop counter */ 00290 tapCnt--; 00291 } 00292 00293 /* Calculate remaining number of copies */ 00294 tapCnt = (numTaps - 1u) % 0x4u; 00295 00296 /* Copy the remaining q31_t data */ 00297 while(tapCnt > 0u) 00298 { 00299 *pStateCurnt++ = *pState++; 00300 00301 /* Decrement the loop counter */ 00302 tapCnt--; 00303 } 00304 00305 #else 00306 00307 /* Run the below code for Cortex-M0 */ 00308 00309 q31_t *px; /* Temporary pointer for state */ 00310 q31_t *pb; /* Temporary pointer for coefficient buffer */ 00311 q63_t acc; /* Accumulator */ 00312 uint32_t numTaps = S->numTaps; /* Length of the filter */ 00313 uint32_t i, tapCnt, blkCnt; /* Loop counters */ 00314 00315 /* S->pState buffer contains previous frame (numTaps - 1) samples */ 00316 /* pStateCurnt points to the location where the new input data should be written */ 00317 pStateCurnt = &(S->pState[(numTaps - 1u)]); 00318 00319 /* Initialize blkCnt with blockSize */ 00320 blkCnt = blockSize; 00321 00322 while(blkCnt > 0u) 00323 { 00324 /* Copy one sample at a time into state buffer */ 00325 *pStateCurnt++ = *pSrc++; 00326 00327 /* Set the accumulator to zero */ 00328 acc = 0; 00329 00330 /* Initialize state pointer */ 00331 px = pState; 00332 00333 /* Initialize Coefficient pointer */ 00334 pb = pCoeffs; 00335 00336 i = numTaps; 00337 00338 /* Perform the multiply-accumulates */ 00339 do 00340 { 00341 /* acc = b[numTaps-1] * x[n-numTaps-1] + b[numTaps-2] * x[n-numTaps-2] + b[numTaps-3] * x[n-numTaps-3] +...+ b[0] * x[0] */ 00342 acc += (q63_t) * px++ * *pb++; 00343 i--; 00344 } while(i > 0u); 00345 00346 /* The result is in 2.62 format. Convert to 1.31 00347 ** Then store the output in the destination buffer. */ 00348 *pDst++ = (q31_t) (acc >> 31u); 00349 00350 /* Advance state pointer by 1 for the next sample */ 00351 pState = pState + 1; 00352 00353 /* Decrement the samples loop counter */ 00354 blkCnt--; 00355 } 00356 00357 /* Processing is complete. 00358 ** Now copy the last numTaps - 1 samples to the starting of the state buffer. 00359 ** This prepares the state buffer for the next function call. */ 00360 00361 /* Points to the start of the state buffer */ 00362 pStateCurnt = S->pState; 00363 00364 /* Copy numTaps number of values */ 00365 tapCnt = numTaps - 1u; 00366 00367 /* Copy the data */ 00368 while(tapCnt > 0u) 00369 { 00370 *pStateCurnt++ = *pState++; 00371 00372 /* Decrement the loop counter */ 00373 tapCnt--; 00374 } 00375 00376 00377 #endif /* #ifndef ARM_MATH_CM0 */ 00378 00379 } 00380