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CMSIS DSP library

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cmsis_dsp/FilteringFunctions/arm_fir_q31.c@5:3762170b6d4d, 2015-11-20 (annotated)

Committer:
mbed_official
Date:
Fri Nov 20 08:45:18 2015 +0000
Revision:
5:3762170b6d4d
Parent:
3:7a284390b0ce 
Synchronized with git revision 2eb940b9a73af188d3004a2575fdfbb05febe62b



Full URL: https://github.com/mbedmicro/mbed/commit/2eb940b9a73af188d3004a2575fdfbb05febe62b/



Added option to build rpc library. closes #1426

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
mbed_official 5:3762170b6d4d 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
mbed_official 5:3762170b6d4d 4 * $Date: 19. March 2015
mbed_official 5:3762170b6d4d 5 * $Revision: V.1.4.5
emilmont 1:fdd22bb7aa52 6 *
emilmont 2:da51fb522205 7 * Project: CMSIS DSP Library
emilmont 2:da51fb522205 8 * Title: arm_fir_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 2:da51fb522205 10 * Description: Q31 FIR filter processing function.
emilmont 1:fdd22bb7aa52 11 *
emilmont 1:fdd22bb7aa52 12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
emilmont 1:fdd22bb7aa52 13 *
mbed_official 3:7a284390b0ce 14 * Redistribution and use in source and binary forms, with or without
mbed_official 3:7a284390b0ce 15 * modification, are permitted provided that the following conditions
mbed_official 3:7a284390b0ce 16 * are met:
mbed_official 3:7a284390b0ce 17 * - Redistributions of source code must retain the above copyright
mbed_official 3:7a284390b0ce 18 * notice, this list of conditions and the following disclaimer.
mbed_official 3:7a284390b0ce 19 * - Redistributions in binary form must reproduce the above copyright
mbed_official 3:7a284390b0ce 20 * notice, this list of conditions and the following disclaimer in
mbed_official 3:7a284390b0ce 21 * the documentation and/or other materials provided with the
mbed_official 3:7a284390b0ce 22 * distribution.
mbed_official 3:7a284390b0ce 23 * - Neither the name of ARM LIMITED nor the names of its contributors
mbed_official 3:7a284390b0ce 24 * may be used to endorse or promote products derived from this
mbed_official 3:7a284390b0ce 25 * software without specific prior written permission.
mbed_official 3:7a284390b0ce 26 *
mbed_official 3:7a284390b0ce 27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
mbed_official 3:7a284390b0ce 28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
mbed_official 3:7a284390b0ce 29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
mbed_official 3:7a284390b0ce 30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
mbed_official 3:7a284390b0ce 31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
mbed_official 3:7a284390b0ce 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
mbed_official 3:7a284390b0ce 33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
mbed_official 3:7a284390b0ce 34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
mbed_official 3:7a284390b0ce 35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
mbed_official 3:7a284390b0ce 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
mbed_official 3:7a284390b0ce 37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
mbed_official 3:7a284390b0ce 38 * POSSIBILITY OF SUCH DAMAGE.
emilmont 1:fdd22bb7aa52 39 * -------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 40
emilmont 1:fdd22bb7aa52 41 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 42
emilmont 1:fdd22bb7aa52 43 /**
emilmont 1:fdd22bb7aa52 44 * @ingroup groupFilters
emilmont 1:fdd22bb7aa52 45 */
emilmont 1:fdd22bb7aa52 46
emilmont 1:fdd22bb7aa52 47 /**
emilmont 1:fdd22bb7aa52 48 * @addtogroup FIR
emilmont 1:fdd22bb7aa52 49 * @{
emilmont 1:fdd22bb7aa52 50 */
emilmont 1:fdd22bb7aa52 51
emilmont 1:fdd22bb7aa52 52 /**
emilmont 1:fdd22bb7aa52 53 * @param[in] *S points to an instance of the Q31 FIR filter structure.
emilmont 1:fdd22bb7aa52 54 * @param[in] *pSrc points to the block of input data.
emilmont 1:fdd22bb7aa52 55 * @param[out] *pDst points to the block of output data.
emilmont 1:fdd22bb7aa52 56 * @param[in] blockSize number of samples to process per call.
emilmont 1:fdd22bb7aa52 57 * @return none.
emilmont 1:fdd22bb7aa52 58 *
emilmont 1:fdd22bb7aa52 59 * @details
emilmont 1:fdd22bb7aa52 60 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 61 * \par
emilmont 1:fdd22bb7aa52 62 * The function is implemented using an internal 64-bit accumulator.
emilmont 1:fdd22bb7aa52 63 * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
emilmont 1:fdd22bb7aa52 64 * Thus, if the accumulator result overflows it wraps around rather than clip.
emilmont 1:fdd22bb7aa52 65 * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits.
emilmont 1:fdd22bb7aa52 66 * After all multiply-accumulates are performed, the 2.62 accumulator is right shifted by 31 bits and saturated to 1.31 format to yield the final result.
emilmont 1:fdd22bb7aa52 67 *
emilmont 1:fdd22bb7aa52 68 * \par
emilmont 1:fdd22bb7aa52 69 * Refer to the function <code>arm_fir_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
emilmont 1:fdd22bb7aa52 70 */
emilmont 1:fdd22bb7aa52 71
emilmont 1:fdd22bb7aa52 72 void arm_fir_q31(
emilmont 1:fdd22bb7aa52 73 const arm_fir_instance_q31 * S,
emilmont 1:fdd22bb7aa52 74 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 75 q31_t * pDst,
emilmont 1:fdd22bb7aa52 76 uint32_t blockSize)
emilmont 1:fdd22bb7aa52 77 {
emilmont 1:fdd22bb7aa52 78 q31_t *pState = S->pState; /* State pointer */
emilmont 1:fdd22bb7aa52 79 q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
emilmont 1:fdd22bb7aa52 80 q31_t *pStateCurnt; /* Points to the current sample of the state */
emilmont 1:fdd22bb7aa52 81
emilmont 1:fdd22bb7aa52 82
mbed_official 3:7a284390b0ce 83 #ifndef ARM_MATH_CM0_FAMILY
emilmont 1:fdd22bb7aa52 84
emilmont 1:fdd22bb7aa52 85 /* Run the below code for Cortex-M4 and Cortex-M3 */
emilmont 1:fdd22bb7aa52 86
emilmont 1:fdd22bb7aa52 87 q31_t x0, x1, x2; /* Temporary variables to hold state */
emilmont 1:fdd22bb7aa52 88 q31_t c0; /* Temporary variable to hold coefficient value */
emilmont 1:fdd22bb7aa52 89 q31_t *px; /* Temporary pointer for state */
emilmont 1:fdd22bb7aa52 90 q31_t *pb; /* Temporary pointer for coefficient buffer */
emilmont 1:fdd22bb7aa52 91 q63_t acc0, acc1, acc2; /* Accumulators */
emilmont 1:fdd22bb7aa52 92 uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */
emilmont 1:fdd22bb7aa52 93 uint32_t i, tapCnt, blkCnt, tapCntN3; /* Loop counters */
emilmont 1:fdd22bb7aa52 94
emilmont 1:fdd22bb7aa52 95 /* S->pState points to state array which contains previous frame (numTaps - 1) samples */
emilmont 1:fdd22bb7aa52 96 /* pStateCurnt points to the location where the new input data should be written */
emilmont 1:fdd22bb7aa52 97 pStateCurnt = &(S->pState[(numTaps - 1u)]);
emilmont 1:fdd22bb7aa52 98
emilmont 1:fdd22bb7aa52 99 /* Apply loop unrolling and compute 4 output values simultaneously.
emilmont 1:fdd22bb7aa52 100 * The variables acc0 ... acc3 hold output values that are being computed:
emilmont 1:fdd22bb7aa52 101 *
emilmont 1:fdd22bb7aa52 102 * 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]
emilmont 1:fdd22bb7aa52 103 * 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]
emilmont 1:fdd22bb7aa52 104 * 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]
emilmont 1:fdd22bb7aa52 105 * 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]
emilmont 1:fdd22bb7aa52 106 */
emilmont 1:fdd22bb7aa52 107 blkCnt = blockSize / 3;
emilmont 1:fdd22bb7aa52 108 blockSize = blockSize - (3 * blkCnt);
emilmont 1:fdd22bb7aa52 109
emilmont 1:fdd22bb7aa52 110 tapCnt = numTaps / 3;
emilmont 1:fdd22bb7aa52 111 tapCntN3 = numTaps - (3 * tapCnt);
emilmont 1:fdd22bb7aa52 112
emilmont 1:fdd22bb7aa52 113 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emilmont 1:fdd22bb7aa52 114 ** a second loop below computes the remaining 1 to 3 samples. */
emilmont 1:fdd22bb7aa52 115 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 116 {
emilmont 1:fdd22bb7aa52 117 /* Copy three new input samples into the state buffer */
emilmont 1:fdd22bb7aa52 118 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 119 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 120 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 121
emilmont 1:fdd22bb7aa52 122 /* Set all accumulators to zero */
emilmont 1:fdd22bb7aa52 123 acc0 = 0;
emilmont 1:fdd22bb7aa52 124 acc1 = 0;
emilmont 1:fdd22bb7aa52 125 acc2 = 0;
emilmont 1:fdd22bb7aa52 126
emilmont 1:fdd22bb7aa52 127 /* Initialize state pointer */
emilmont 1:fdd22bb7aa52 128 px = pState;
emilmont 1:fdd22bb7aa52 129
emilmont 1:fdd22bb7aa52 130 /* Initialize coefficient pointer */
emilmont 1:fdd22bb7aa52 131 pb = pCoeffs;
emilmont 1:fdd22bb7aa52 132
emilmont 1:fdd22bb7aa52 133 /* Read the first two samples from the state buffer:
emilmont 1:fdd22bb7aa52 134 * x[n-numTaps], x[n-numTaps-1] */
emilmont 1:fdd22bb7aa52 135 x0 = *(px++);
emilmont 1:fdd22bb7aa52 136 x1 = *(px++);
emilmont 1:fdd22bb7aa52 137
emilmont 1:fdd22bb7aa52 138 /* Loop unrolling. Process 3 taps at a time. */
emilmont 1:fdd22bb7aa52 139 i = tapCnt;
emilmont 1:fdd22bb7aa52 140
emilmont 1:fdd22bb7aa52 141 while(i > 0u)
emilmont 1:fdd22bb7aa52 142 {
emilmont 1:fdd22bb7aa52 143 /* Read the b[numTaps] coefficient */
emilmont 1:fdd22bb7aa52 144 c0 = *pb;
emilmont 1:fdd22bb7aa52 145
emilmont 1:fdd22bb7aa52 146 /* Read x[n-numTaps-2] sample */
emilmont 1:fdd22bb7aa52 147 x2 = *(px++);
emilmont 1:fdd22bb7aa52 148
emilmont 1:fdd22bb7aa52 149 /* Perform the multiply-accumulates */
emilmont 1:fdd22bb7aa52 150 acc0 += ((q63_t) x0 * c0);
emilmont 1:fdd22bb7aa52 151 acc1 += ((q63_t) x1 * c0);
emilmont 1:fdd22bb7aa52 152 acc2 += ((q63_t) x2 * c0);
emilmont 1:fdd22bb7aa52 153
emilmont 1:fdd22bb7aa52 154 /* Read the coefficient and state */
emilmont 1:fdd22bb7aa52 155 c0 = *(pb + 1u);
emilmont 1:fdd22bb7aa52 156 x0 = *(px++);
emilmont 1:fdd22bb7aa52 157
emilmont 1:fdd22bb7aa52 158 /* Perform the multiply-accumulates */
emilmont 1:fdd22bb7aa52 159 acc0 += ((q63_t) x1 * c0);
emilmont 1:fdd22bb7aa52 160 acc1 += ((q63_t) x2 * c0);
emilmont 1:fdd22bb7aa52 161 acc2 += ((q63_t) x0 * c0);
emilmont 1:fdd22bb7aa52 162
emilmont 1:fdd22bb7aa52 163 /* Read the coefficient and state */
emilmont 1:fdd22bb7aa52 164 c0 = *(pb + 2u);
emilmont 1:fdd22bb7aa52 165 x1 = *(px++);
emilmont 1:fdd22bb7aa52 166
emilmont 1:fdd22bb7aa52 167 /* update coefficient pointer */
emilmont 1:fdd22bb7aa52 168 pb += 3u;
emilmont 1:fdd22bb7aa52 169
emilmont 1:fdd22bb7aa52 170 /* Perform the multiply-accumulates */
emilmont 1:fdd22bb7aa52 171 acc0 += ((q63_t) x2 * c0);
emilmont 1:fdd22bb7aa52 172 acc1 += ((q63_t) x0 * c0);
emilmont 1:fdd22bb7aa52 173 acc2 += ((q63_t) x1 * c0);
emilmont 1:fdd22bb7aa52 174
emilmont 1:fdd22bb7aa52 175 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 176 i--;
emilmont 1:fdd22bb7aa52 177 }
emilmont 1:fdd22bb7aa52 178
emilmont 1:fdd22bb7aa52 179 /* If the filter length is not a multiple of 3, compute the remaining filter taps */
emilmont 1:fdd22bb7aa52 180
emilmont 1:fdd22bb7aa52 181 i = tapCntN3;
emilmont 1:fdd22bb7aa52 182
emilmont 1:fdd22bb7aa52 183 while(i > 0u)
emilmont 1:fdd22bb7aa52 184 {
emilmont 1:fdd22bb7aa52 185 /* Read coefficients */
emilmont 1:fdd22bb7aa52 186 c0 = *(pb++);
emilmont 1:fdd22bb7aa52 187
emilmont 1:fdd22bb7aa52 188 /* Fetch 1 state variable */
emilmont 1:fdd22bb7aa52 189 x2 = *(px++);
emilmont 1:fdd22bb7aa52 190
emilmont 1:fdd22bb7aa52 191 /* Perform the multiply-accumulates */
emilmont 1:fdd22bb7aa52 192 acc0 += ((q63_t) x0 * c0);
emilmont 1:fdd22bb7aa52 193 acc1 += ((q63_t) x1 * c0);
emilmont 1:fdd22bb7aa52 194 acc2 += ((q63_t) x2 * c0);
emilmont 1:fdd22bb7aa52 195
emilmont 1:fdd22bb7aa52 196 /* Reuse the present sample states for next sample */
emilmont 1:fdd22bb7aa52 197 x0 = x1;
emilmont 1:fdd22bb7aa52 198 x1 = x2;
emilmont 1:fdd22bb7aa52 199
emilmont 1:fdd22bb7aa52 200 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 201 i--;
emilmont 1:fdd22bb7aa52 202 }
emilmont 1:fdd22bb7aa52 203
emilmont 1:fdd22bb7aa52 204 /* Advance the state pointer by 3 to process the next group of 3 samples */
emilmont 1:fdd22bb7aa52 205 pState = pState + 3;
emilmont 1:fdd22bb7aa52 206
emilmont 1:fdd22bb7aa52 207 /* The results in the 3 accumulators are in 2.30 format. Convert to 1.31
emilmont 1:fdd22bb7aa52 208 ** Then store the 3 outputs in the destination buffer. */
emilmont 1:fdd22bb7aa52 209 *pDst++ = (q31_t) (acc0 >> 31u);
emilmont 1:fdd22bb7aa52 210 *pDst++ = (q31_t) (acc1 >> 31u);
emilmont 1:fdd22bb7aa52 211 *pDst++ = (q31_t) (acc2 >> 31u);
emilmont 1:fdd22bb7aa52 212
emilmont 1:fdd22bb7aa52 213 /* Decrement the samples loop counter */
emilmont 1:fdd22bb7aa52 214 blkCnt--;
emilmont 1:fdd22bb7aa52 215 }
emilmont 1:fdd22bb7aa52 216
emilmont 1:fdd22bb7aa52 217 /* If the blockSize is not a multiple of 3, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 218 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 219
emilmont 1:fdd22bb7aa52 220 while(blockSize > 0u)
emilmont 1:fdd22bb7aa52 221 {
emilmont 1:fdd22bb7aa52 222 /* Copy one sample at a time into state buffer */
emilmont 1:fdd22bb7aa52 223 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 224
emilmont 1:fdd22bb7aa52 225 /* Set the accumulator to zero */
emilmont 1:fdd22bb7aa52 226 acc0 = 0;
emilmont 1:fdd22bb7aa52 227
emilmont 1:fdd22bb7aa52 228 /* Initialize state pointer */
emilmont 1:fdd22bb7aa52 229 px = pState;
emilmont 1:fdd22bb7aa52 230
emilmont 1:fdd22bb7aa52 231 /* Initialize Coefficient pointer */
emilmont 1:fdd22bb7aa52 232 pb = (pCoeffs);
emilmont 1:fdd22bb7aa52 233
emilmont 1:fdd22bb7aa52 234 i = numTaps;
emilmont 1:fdd22bb7aa52 235
emilmont 1:fdd22bb7aa52 236 /* Perform the multiply-accumulates */
emilmont 1:fdd22bb7aa52 237 do
emilmont 1:fdd22bb7aa52 238 {
emilmont 1:fdd22bb7aa52 239 acc0 += (q63_t) * (px++) * (*(pb++));
emilmont 1:fdd22bb7aa52 240 i--;
emilmont 1:fdd22bb7aa52 241 } while(i > 0u);
emilmont 1:fdd22bb7aa52 242
emilmont 1:fdd22bb7aa52 243 /* The result is in 2.62 format. Convert to 1.31
emilmont 1:fdd22bb7aa52 244 ** Then store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 245 *pDst++ = (q31_t) (acc0 >> 31u);
emilmont 1:fdd22bb7aa52 246
emilmont 1:fdd22bb7aa52 247 /* Advance state pointer by 1 for the next sample */
emilmont 1:fdd22bb7aa52 248 pState = pState + 1;
emilmont 1:fdd22bb7aa52 249
emilmont 1:fdd22bb7aa52 250 /* Decrement the samples loop counter */
emilmont 1:fdd22bb7aa52 251 blockSize--;
emilmont 1:fdd22bb7aa52 252 }
emilmont 1:fdd22bb7aa52 253
emilmont 1:fdd22bb7aa52 254 /* Processing is complete.
emilmont 1:fdd22bb7aa52 255 ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
emilmont 1:fdd22bb7aa52 256 ** This prepares the state buffer for the next function call. */
emilmont 1:fdd22bb7aa52 257
emilmont 1:fdd22bb7aa52 258 /* Points to the start of the state buffer */
emilmont 1:fdd22bb7aa52 259 pStateCurnt = S->pState;
emilmont 1:fdd22bb7aa52 260
emilmont 1:fdd22bb7aa52 261 tapCnt = (numTaps - 1u) >> 2u;
emilmont 1:fdd22bb7aa52 262
emilmont 1:fdd22bb7aa52 263 /* copy data */
emilmont 1:fdd22bb7aa52 264 while(tapCnt > 0u)
emilmont 1:fdd22bb7aa52 265 {
emilmont 1:fdd22bb7aa52 266 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 267 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 268 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 269 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 270
emilmont 1:fdd22bb7aa52 271 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 272 tapCnt--;
emilmont 1:fdd22bb7aa52 273 }
emilmont 1:fdd22bb7aa52 274
emilmont 1:fdd22bb7aa52 275 /* Calculate remaining number of copies */
emilmont 1:fdd22bb7aa52 276 tapCnt = (numTaps - 1u) % 0x4u;
emilmont 1:fdd22bb7aa52 277
emilmont 1:fdd22bb7aa52 278 /* Copy the remaining q31_t data */
emilmont 1:fdd22bb7aa52 279 while(tapCnt > 0u)
emilmont 1:fdd22bb7aa52 280 {
emilmont 1:fdd22bb7aa52 281 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 282
emilmont 1:fdd22bb7aa52 283 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 284 tapCnt--;
emilmont 1:fdd22bb7aa52 285 }
emilmont 1:fdd22bb7aa52 286
emilmont 1:fdd22bb7aa52 287 #else
emilmont 1:fdd22bb7aa52 288
emilmont 1:fdd22bb7aa52 289 /* Run the below code for Cortex-M0 */
emilmont 1:fdd22bb7aa52 290
emilmont 1:fdd22bb7aa52 291 q31_t *px; /* Temporary pointer for state */
emilmont 1:fdd22bb7aa52 292 q31_t *pb; /* Temporary pointer for coefficient buffer */
emilmont 1:fdd22bb7aa52 293 q63_t acc; /* Accumulator */
emilmont 1:fdd22bb7aa52 294 uint32_t numTaps = S->numTaps; /* Length of the filter */
emilmont 1:fdd22bb7aa52 295 uint32_t i, tapCnt, blkCnt; /* Loop counters */
emilmont 1:fdd22bb7aa52 296
emilmont 1:fdd22bb7aa52 297 /* S->pState buffer contains previous frame (numTaps - 1) samples */
emilmont 1:fdd22bb7aa52 298 /* pStateCurnt points to the location where the new input data should be written */
emilmont 1:fdd22bb7aa52 299 pStateCurnt = &(S->pState[(numTaps - 1u)]);
emilmont 1:fdd22bb7aa52 300
emilmont 1:fdd22bb7aa52 301 /* Initialize blkCnt with blockSize */
emilmont 1:fdd22bb7aa52 302 blkCnt = blockSize;
emilmont 1:fdd22bb7aa52 303
emilmont 1:fdd22bb7aa52 304 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 305 {
emilmont 1:fdd22bb7aa52 306 /* Copy one sample at a time into state buffer */
emilmont 1:fdd22bb7aa52 307 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 308
emilmont 1:fdd22bb7aa52 309 /* Set the accumulator to zero */
emilmont 1:fdd22bb7aa52 310 acc = 0;
emilmont 1:fdd22bb7aa52 311
emilmont 1:fdd22bb7aa52 312 /* Initialize state pointer */
emilmont 1:fdd22bb7aa52 313 px = pState;
emilmont 1:fdd22bb7aa52 314
emilmont 1:fdd22bb7aa52 315 /* Initialize Coefficient pointer */
emilmont 1:fdd22bb7aa52 316 pb = pCoeffs;
emilmont 1:fdd22bb7aa52 317
emilmont 1:fdd22bb7aa52 318 i = numTaps;
emilmont 1:fdd22bb7aa52 319
emilmont 1:fdd22bb7aa52 320 /* Perform the multiply-accumulates */
emilmont 1:fdd22bb7aa52 321 do
emilmont 1:fdd22bb7aa52 322 {
emilmont 1:fdd22bb7aa52 323 /* 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] */
emilmont 1:fdd22bb7aa52 324 acc += (q63_t) * px++ * *pb++;
emilmont 1:fdd22bb7aa52 325 i--;
emilmont 1:fdd22bb7aa52 326 } while(i > 0u);
emilmont 1:fdd22bb7aa52 327
emilmont 1:fdd22bb7aa52 328 /* The result is in 2.62 format. Convert to 1.31
emilmont 1:fdd22bb7aa52 329 ** Then store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 330 *pDst++ = (q31_t) (acc >> 31u);
emilmont 1:fdd22bb7aa52 331
emilmont 1:fdd22bb7aa52 332 /* Advance state pointer by 1 for the next sample */
emilmont 1:fdd22bb7aa52 333 pState = pState + 1;
emilmont 1:fdd22bb7aa52 334
emilmont 1:fdd22bb7aa52 335 /* Decrement the samples loop counter */
emilmont 1:fdd22bb7aa52 336 blkCnt--;
emilmont 1:fdd22bb7aa52 337 }
emilmont 1:fdd22bb7aa52 338
emilmont 1:fdd22bb7aa52 339 /* Processing is complete.
emilmont 1:fdd22bb7aa52 340 ** Now copy the last numTaps - 1 samples to the starting of the state buffer.
emilmont 1:fdd22bb7aa52 341 ** This prepares the state buffer for the next function call. */
emilmont 1:fdd22bb7aa52 342
emilmont 1:fdd22bb7aa52 343 /* Points to the start of the state buffer */
emilmont 1:fdd22bb7aa52 344 pStateCurnt = S->pState;
emilmont 1:fdd22bb7aa52 345
emilmont 1:fdd22bb7aa52 346 /* Copy numTaps number of values */
emilmont 1:fdd22bb7aa52 347 tapCnt = numTaps - 1u;
emilmont 1:fdd22bb7aa52 348
emilmont 1:fdd22bb7aa52 349 /* Copy the data */
emilmont 1:fdd22bb7aa52 350 while(tapCnt > 0u)
emilmont 1:fdd22bb7aa52 351 {
emilmont 1:fdd22bb7aa52 352 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 353
emilmont 1:fdd22bb7aa52 354 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 355 tapCnt--;
emilmont 1:fdd22bb7aa52 356 }
emilmont 1:fdd22bb7aa52 357
emilmont 1:fdd22bb7aa52 358
mbed_official 3:7a284390b0ce 359 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
emilmont 1:fdd22bb7aa52 360
emilmont 1:fdd22bb7aa52 361 }
emilmont 1:fdd22bb7aa52 362
emilmont 1:fdd22bb7aa52 363 /**
emilmont 1:fdd22bb7aa52 364 * @} end of FIR group
emilmont 1:fdd22bb7aa52 365 */