Eli Hughes / CMSIS_DSP_401

V4.0.1 of the ARM CMSIS DSP libraries. Note that arm_bitreversal2.s, arm_cfft_f32.c and arm_rfft_fast_f32.c had to be removed. arm_bitreversal2.s will not assemble with the online tools. So, the fast f32 FFT functions are not yet available. All the other FFT functions are available.

Dependents:   MPU9150_Example fir_f32 fir_f32 MPU9150_nucleo_noni2cdev ... more

FilteringFunctions/arm_fir_decimate_fast_q31.c@0:3d9c67d97d6f, 2014-07-28 (annotated)

Committer:
emh203
Date:
Mon Jul 28 15:03:15 2014 +0000
Revision:
0:3d9c67d97d6f
1st working commit.   Had to remove arm_bitreversal2.s     arm_cfft_f32.c and arm_rfft_fast_f32.c.    The .s will not assemble.      For now I removed these functions so we could at least have a library for the other functions.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emh203 0:3d9c67d97d6f 1 /* ----------------------------------------------------------------------
emh203 0:3d9c67d97d6f 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
emh203 0:3d9c67d97d6f 3 *
emh203 0:3d9c67d97d6f 4 * $Date: 12. March 2014
emh203 0:3d9c67d97d6f 5 * $Revision: V1.4.3
emh203 0:3d9c67d97d6f 6 *
emh203 0:3d9c67d97d6f 7 * Project: CMSIS DSP Library
emh203 0:3d9c67d97d6f 8 * Title: arm_fir_decimate_fast_q31.c
emh203 0:3d9c67d97d6f 9 *
emh203 0:3d9c67d97d6f 10 * Description: Fast Q31 FIR Decimator.
emh203 0:3d9c67d97d6f 11 *
emh203 0:3d9c67d97d6f 12 * Target Processor: Cortex-M4/Cortex-M3
emh203 0:3d9c67d97d6f 13 *
emh203 0:3d9c67d97d6f 14 * Redistribution and use in source and binary forms, with or without
emh203 0:3d9c67d97d6f 15 * modification, are permitted provided that the following conditions
emh203 0:3d9c67d97d6f 16 * are met:
emh203 0:3d9c67d97d6f 17 * - Redistributions of source code must retain the above copyright
emh203 0:3d9c67d97d6f 18 * notice, this list of conditions and the following disclaimer.
emh203 0:3d9c67d97d6f 19 * - Redistributions in binary form must reproduce the above copyright
emh203 0:3d9c67d97d6f 20 * notice, this list of conditions and the following disclaimer in
emh203 0:3d9c67d97d6f 21 * the documentation and/or other materials provided with the
emh203 0:3d9c67d97d6f 22 * distribution.
emh203 0:3d9c67d97d6f 23 * - Neither the name of ARM LIMITED nor the names of its contributors
emh203 0:3d9c67d97d6f 24 * may be used to endorse or promote products derived from this
emh203 0:3d9c67d97d6f 25 * software without specific prior written permission.
emh203 0:3d9c67d97d6f 26 *
emh203 0:3d9c67d97d6f 27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
emh203 0:3d9c67d97d6f 28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
emh203 0:3d9c67d97d6f 29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
emh203 0:3d9c67d97d6f 30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
emh203 0:3d9c67d97d6f 31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
emh203 0:3d9c67d97d6f 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
emh203 0:3d9c67d97d6f 33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
emh203 0:3d9c67d97d6f 34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
emh203 0:3d9c67d97d6f 35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
emh203 0:3d9c67d97d6f 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
emh203 0:3d9c67d97d6f 37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
emh203 0:3d9c67d97d6f 38 * POSSIBILITY OF SUCH DAMAGE.
emh203 0:3d9c67d97d6f 39 * -------------------------------------------------------------------- */
emh203 0:3d9c67d97d6f 40
emh203 0:3d9c67d97d6f 41 #include "arm_math.h"
emh203 0:3d9c67d97d6f 42
emh203 0:3d9c67d97d6f 43 /**
emh203 0:3d9c67d97d6f 44 * @ingroup groupFilters
emh203 0:3d9c67d97d6f 45 */
emh203 0:3d9c67d97d6f 46
emh203 0:3d9c67d97d6f 47 /**
emh203 0:3d9c67d97d6f 48 * @addtogroup FIR_decimate
emh203 0:3d9c67d97d6f 49 * @{
emh203 0:3d9c67d97d6f 50 */
emh203 0:3d9c67d97d6f 51
emh203 0:3d9c67d97d6f 52 /**
emh203 0:3d9c67d97d6f 53 * @brief Processing function for the Q31 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4.
emh203 0:3d9c67d97d6f 54 * @param[in] *S points to an instance of the Q31 FIR decimator structure.
emh203 0:3d9c67d97d6f 55 * @param[in] *pSrc points to the block of input data.
emh203 0:3d9c67d97d6f 56 * @param[out] *pDst points to the block of output data
emh203 0:3d9c67d97d6f 57 * @param[in] blockSize number of input samples to process per call.
emh203 0:3d9c67d97d6f 58 * @return none
emh203 0:3d9c67d97d6f 59 *
emh203 0:3d9c67d97d6f 60 * <b>Scaling and Overflow Behavior:</b>
emh203 0:3d9c67d97d6f 61 *
emh203 0:3d9c67d97d6f 62 * \par
emh203 0:3d9c67d97d6f 63 * This function is optimized for speed at the expense of fixed-point precision and overflow protection.
emh203 0:3d9c67d97d6f 64 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
emh203 0:3d9c67d97d6f 65 * These intermediate results are added to a 2.30 accumulator.
emh203 0:3d9c67d97d6f 66 * Finally, the accumulator is saturated and converted to a 1.31 result.
emh203 0:3d9c67d97d6f 67 * The fast version has the same overflow behavior as the standard version and provides less precision since it discards the low 32 bits of each multiplication result.
emh203 0:3d9c67d97d6f 68 * In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits (where log2 is read as log to the base 2).
emh203 0:3d9c67d97d6f 69 *
emh203 0:3d9c67d97d6f 70 * \par
emh203 0:3d9c67d97d6f 71 * Refer to the function <code>arm_fir_decimate_q31()</code> for a slower implementation of this function which uses a 64-bit accumulator to provide higher precision.
emh203 0:3d9c67d97d6f 72 * Both the slow and the fast versions use the same instance structure.
emh203 0:3d9c67d97d6f 73 * Use the function <code>arm_fir_decimate_init_q31()</code> to initialize the filter structure.
emh203 0:3d9c67d97d6f 74 */
emh203 0:3d9c67d97d6f 75
emh203 0:3d9c67d97d6f 76 void arm_fir_decimate_fast_q31(
emh203 0:3d9c67d97d6f 77 arm_fir_decimate_instance_q31 * S,
emh203 0:3d9c67d97d6f 78 q31_t * pSrc,
emh203 0:3d9c67d97d6f 79 q31_t * pDst,
emh203 0:3d9c67d97d6f 80 uint32_t blockSize)
emh203 0:3d9c67d97d6f 81 {
emh203 0:3d9c67d97d6f 82 q31_t *pState = S->pState; /* State pointer */
emh203 0:3d9c67d97d6f 83 q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
emh203 0:3d9c67d97d6f 84 q31_t *pStateCurnt; /* Points to the current sample of the state */
emh203 0:3d9c67d97d6f 85 q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
emh203 0:3d9c67d97d6f 86 q31_t *px; /* Temporary pointers for state buffer */
emh203 0:3d9c67d97d6f 87 q31_t *pb; /* Temporary pointers for coefficient buffer */
emh203 0:3d9c67d97d6f 88 q31_t sum0; /* Accumulator */
emh203 0:3d9c67d97d6f 89 uint32_t numTaps = S->numTaps; /* Number of taps */
emh203 0:3d9c67d97d6f 90 uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */
emh203 0:3d9c67d97d6f 91 uint32_t blkCntN2;
emh203 0:3d9c67d97d6f 92 q31_t x1;
emh203 0:3d9c67d97d6f 93 q31_t acc0, acc1;
emh203 0:3d9c67d97d6f 94 q31_t *px0, *px1;
emh203 0:3d9c67d97d6f 95
emh203 0:3d9c67d97d6f 96 /* S->pState buffer contains previous frame (numTaps - 1) samples */
emh203 0:3d9c67d97d6f 97 /* pStateCurnt points to the location where the new input data should be written */
emh203 0:3d9c67d97d6f 98 pStateCurnt = S->pState + (numTaps - 1u);
emh203 0:3d9c67d97d6f 99
emh203 0:3d9c67d97d6f 100 /* Total number of output samples to be computed */
emh203 0:3d9c67d97d6f 101
emh203 0:3d9c67d97d6f 102 blkCnt = outBlockSize / 2;
emh203 0:3d9c67d97d6f 103 blkCntN2 = outBlockSize - (2 * blkCnt);
emh203 0:3d9c67d97d6f 104
emh203 0:3d9c67d97d6f 105 while(blkCnt > 0u)
emh203 0:3d9c67d97d6f 106 {
emh203 0:3d9c67d97d6f 107 /* Copy decimation factor number of new input samples into the state buffer */
emh203 0:3d9c67d97d6f 108 i = 2 * S->M;
emh203 0:3d9c67d97d6f 109
emh203 0:3d9c67d97d6f 110 do
emh203 0:3d9c67d97d6f 111 {
emh203 0:3d9c67d97d6f 112 *pStateCurnt++ = *pSrc++;
emh203 0:3d9c67d97d6f 113
emh203 0:3d9c67d97d6f 114 } while(--i);
emh203 0:3d9c67d97d6f 115
emh203 0:3d9c67d97d6f 116 /* Set accumulator to zero */
emh203 0:3d9c67d97d6f 117 acc0 = 0;
emh203 0:3d9c67d97d6f 118 acc1 = 0;
emh203 0:3d9c67d97d6f 119
emh203 0:3d9c67d97d6f 120 /* Initialize state pointer */
emh203 0:3d9c67d97d6f 121 px0 = pState;
emh203 0:3d9c67d97d6f 122 px1 = pState + S->M;
emh203 0:3d9c67d97d6f 123
emh203 0:3d9c67d97d6f 124 /* Initialize coeff pointer */
emh203 0:3d9c67d97d6f 125 pb = pCoeffs;
emh203 0:3d9c67d97d6f 126
emh203 0:3d9c67d97d6f 127 /* Loop unrolling. Process 4 taps at a time. */
emh203 0:3d9c67d97d6f 128 tapCnt = numTaps >> 2;
emh203 0:3d9c67d97d6f 129
emh203 0:3d9c67d97d6f 130 /* Loop over the number of taps. Unroll by a factor of 4.
emh203 0:3d9c67d97d6f 131 ** Repeat until we've computed numTaps-4 coefficients. */
emh203 0:3d9c67d97d6f 132 while(tapCnt > 0u)
emh203 0:3d9c67d97d6f 133 {
emh203 0:3d9c67d97d6f 134 /* Read the b[numTaps-1] coefficient */
emh203 0:3d9c67d97d6f 135 c0 = *(pb);
emh203 0:3d9c67d97d6f 136
emh203 0:3d9c67d97d6f 137 /* Read x[n-numTaps-1] for sample 0 sample 1 */
emh203 0:3d9c67d97d6f 138 x0 = *(px0);
emh203 0:3d9c67d97d6f 139 x1 = *(px1);
emh203 0:3d9c67d97d6f 140
emh203 0:3d9c67d97d6f 141 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 142 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 143 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emh203 0:3d9c67d97d6f 144
emh203 0:3d9c67d97d6f 145 /* Read the b[numTaps-2] coefficient */
emh203 0:3d9c67d97d6f 146 c0 = *(pb + 1u);
emh203 0:3d9c67d97d6f 147
emh203 0:3d9c67d97d6f 148 /* Read x[n-numTaps-2] for sample 0 sample 1 */
emh203 0:3d9c67d97d6f 149 x0 = *(px0 + 1u);
emh203 0:3d9c67d97d6f 150 x1 = *(px1 + 1u);
emh203 0:3d9c67d97d6f 151
emh203 0:3d9c67d97d6f 152 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 153 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 154 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emh203 0:3d9c67d97d6f 155
emh203 0:3d9c67d97d6f 156 /* Read the b[numTaps-3] coefficient */
emh203 0:3d9c67d97d6f 157 c0 = *(pb + 2u);
emh203 0:3d9c67d97d6f 158
emh203 0:3d9c67d97d6f 159 /* Read x[n-numTaps-3] for sample 0 sample 1 */
emh203 0:3d9c67d97d6f 160 x0 = *(px0 + 2u);
emh203 0:3d9c67d97d6f 161 x1 = *(px1 + 2u);
emh203 0:3d9c67d97d6f 162 pb += 4u;
emh203 0:3d9c67d97d6f 163
emh203 0:3d9c67d97d6f 164 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 165 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 166 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emh203 0:3d9c67d97d6f 167
emh203 0:3d9c67d97d6f 168 /* Read the b[numTaps-4] coefficient */
emh203 0:3d9c67d97d6f 169 c0 = *(pb - 1u);
emh203 0:3d9c67d97d6f 170
emh203 0:3d9c67d97d6f 171 /* Read x[n-numTaps-4] for sample 0 sample 1 */
emh203 0:3d9c67d97d6f 172 x0 = *(px0 + 3u);
emh203 0:3d9c67d97d6f 173 x1 = *(px1 + 3u);
emh203 0:3d9c67d97d6f 174
emh203 0:3d9c67d97d6f 175
emh203 0:3d9c67d97d6f 176 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 177 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 178 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emh203 0:3d9c67d97d6f 179
emh203 0:3d9c67d97d6f 180 /* update state pointers */
emh203 0:3d9c67d97d6f 181 px0 += 4u;
emh203 0:3d9c67d97d6f 182 px1 += 4u;
emh203 0:3d9c67d97d6f 183
emh203 0:3d9c67d97d6f 184 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 185 tapCnt--;
emh203 0:3d9c67d97d6f 186 }
emh203 0:3d9c67d97d6f 187
emh203 0:3d9c67d97d6f 188 /* If the filter length is not a multiple of 4, compute the remaining filter taps */
emh203 0:3d9c67d97d6f 189 tapCnt = numTaps % 0x4u;
emh203 0:3d9c67d97d6f 190
emh203 0:3d9c67d97d6f 191 while(tapCnt > 0u)
emh203 0:3d9c67d97d6f 192 {
emh203 0:3d9c67d97d6f 193 /* Read coefficients */
emh203 0:3d9c67d97d6f 194 c0 = *(pb++);
emh203 0:3d9c67d97d6f 195
emh203 0:3d9c67d97d6f 196 /* Fetch 1 state variable */
emh203 0:3d9c67d97d6f 197 x0 = *(px0++);
emh203 0:3d9c67d97d6f 198 x1 = *(px1++);
emh203 0:3d9c67d97d6f 199
emh203 0:3d9c67d97d6f 200 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 201 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 202 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emh203 0:3d9c67d97d6f 203
emh203 0:3d9c67d97d6f 204 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 205 tapCnt--;
emh203 0:3d9c67d97d6f 206 }
emh203 0:3d9c67d97d6f 207
emh203 0:3d9c67d97d6f 208 /* Advance the state pointer by the decimation factor
emh203 0:3d9c67d97d6f 209 * to process the next group of decimation factor number samples */
emh203 0:3d9c67d97d6f 210 pState = pState + S->M * 2;
emh203 0:3d9c67d97d6f 211
emh203 0:3d9c67d97d6f 212 /* The result is in the accumulator, store in the destination buffer. */
emh203 0:3d9c67d97d6f 213 *pDst++ = (q31_t) (acc0 << 1);
emh203 0:3d9c67d97d6f 214 *pDst++ = (q31_t) (acc1 << 1);
emh203 0:3d9c67d97d6f 215
emh203 0:3d9c67d97d6f 216 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 217 blkCnt--;
emh203 0:3d9c67d97d6f 218 }
emh203 0:3d9c67d97d6f 219
emh203 0:3d9c67d97d6f 220 while(blkCntN2 > 0u)
emh203 0:3d9c67d97d6f 221 {
emh203 0:3d9c67d97d6f 222 /* Copy decimation factor number of new input samples into the state buffer */
emh203 0:3d9c67d97d6f 223 i = S->M;
emh203 0:3d9c67d97d6f 224
emh203 0:3d9c67d97d6f 225 do
emh203 0:3d9c67d97d6f 226 {
emh203 0:3d9c67d97d6f 227 *pStateCurnt++ = *pSrc++;
emh203 0:3d9c67d97d6f 228
emh203 0:3d9c67d97d6f 229 } while(--i);
emh203 0:3d9c67d97d6f 230
emh203 0:3d9c67d97d6f 231 /* Set accumulator to zero */
emh203 0:3d9c67d97d6f 232 sum0 = 0;
emh203 0:3d9c67d97d6f 233
emh203 0:3d9c67d97d6f 234 /* Initialize state pointer */
emh203 0:3d9c67d97d6f 235 px = pState;
emh203 0:3d9c67d97d6f 236
emh203 0:3d9c67d97d6f 237 /* Initialize coeff pointer */
emh203 0:3d9c67d97d6f 238 pb = pCoeffs;
emh203 0:3d9c67d97d6f 239
emh203 0:3d9c67d97d6f 240 /* Loop unrolling. Process 4 taps at a time. */
emh203 0:3d9c67d97d6f 241 tapCnt = numTaps >> 2;
emh203 0:3d9c67d97d6f 242
emh203 0:3d9c67d97d6f 243 /* Loop over the number of taps. Unroll by a factor of 4.
emh203 0:3d9c67d97d6f 244 ** Repeat until we've computed numTaps-4 coefficients. */
emh203 0:3d9c67d97d6f 245 while(tapCnt > 0u)
emh203 0:3d9c67d97d6f 246 {
emh203 0:3d9c67d97d6f 247 /* Read the b[numTaps-1] coefficient */
emh203 0:3d9c67d97d6f 248 c0 = *(pb++);
emh203 0:3d9c67d97d6f 249
emh203 0:3d9c67d97d6f 250 /* Read x[n-numTaps-1] sample */
emh203 0:3d9c67d97d6f 251 x0 = *(px++);
emh203 0:3d9c67d97d6f 252
emh203 0:3d9c67d97d6f 253 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 254 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 255
emh203 0:3d9c67d97d6f 256 /* Read the b[numTaps-2] coefficient */
emh203 0:3d9c67d97d6f 257 c0 = *(pb++);
emh203 0:3d9c67d97d6f 258
emh203 0:3d9c67d97d6f 259 /* Read x[n-numTaps-2] sample */
emh203 0:3d9c67d97d6f 260 x0 = *(px++);
emh203 0:3d9c67d97d6f 261
emh203 0:3d9c67d97d6f 262 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 263 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 264
emh203 0:3d9c67d97d6f 265 /* Read the b[numTaps-3] coefficient */
emh203 0:3d9c67d97d6f 266 c0 = *(pb++);
emh203 0:3d9c67d97d6f 267
emh203 0:3d9c67d97d6f 268 /* Read x[n-numTaps-3] sample */
emh203 0:3d9c67d97d6f 269 x0 = *(px++);
emh203 0:3d9c67d97d6f 270
emh203 0:3d9c67d97d6f 271 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 272 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 273
emh203 0:3d9c67d97d6f 274 /* Read the b[numTaps-4] coefficient */
emh203 0:3d9c67d97d6f 275 c0 = *(pb++);
emh203 0:3d9c67d97d6f 276
emh203 0:3d9c67d97d6f 277 /* Read x[n-numTaps-4] sample */
emh203 0:3d9c67d97d6f 278 x0 = *(px++);
emh203 0:3d9c67d97d6f 279
emh203 0:3d9c67d97d6f 280 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 281 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 282
emh203 0:3d9c67d97d6f 283 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 284 tapCnt--;
emh203 0:3d9c67d97d6f 285 }
emh203 0:3d9c67d97d6f 286
emh203 0:3d9c67d97d6f 287 /* If the filter length is not a multiple of 4, compute the remaining filter taps */
emh203 0:3d9c67d97d6f 288 tapCnt = numTaps % 0x4u;
emh203 0:3d9c67d97d6f 289
emh203 0:3d9c67d97d6f 290 while(tapCnt > 0u)
emh203 0:3d9c67d97d6f 291 {
emh203 0:3d9c67d97d6f 292 /* Read coefficients */
emh203 0:3d9c67d97d6f 293 c0 = *(pb++);
emh203 0:3d9c67d97d6f 294
emh203 0:3d9c67d97d6f 295 /* Fetch 1 state variable */
emh203 0:3d9c67d97d6f 296 x0 = *(px++);
emh203 0:3d9c67d97d6f 297
emh203 0:3d9c67d97d6f 298 /* Perform the multiply-accumulate */
emh203 0:3d9c67d97d6f 299 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emh203 0:3d9c67d97d6f 300
emh203 0:3d9c67d97d6f 301 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 302 tapCnt--;
emh203 0:3d9c67d97d6f 303 }
emh203 0:3d9c67d97d6f 304
emh203 0:3d9c67d97d6f 305 /* Advance the state pointer by the decimation factor
emh203 0:3d9c67d97d6f 306 * to process the next group of decimation factor number samples */
emh203 0:3d9c67d97d6f 307 pState = pState + S->M;
emh203 0:3d9c67d97d6f 308
emh203 0:3d9c67d97d6f 309 /* The result is in the accumulator, store in the destination buffer. */
emh203 0:3d9c67d97d6f 310 *pDst++ = (q31_t) (sum0 << 1);
emh203 0:3d9c67d97d6f 311
emh203 0:3d9c67d97d6f 312 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 313 blkCntN2--;
emh203 0:3d9c67d97d6f 314 }
emh203 0:3d9c67d97d6f 315
emh203 0:3d9c67d97d6f 316 /* Processing is complete.
emh203 0:3d9c67d97d6f 317 ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
emh203 0:3d9c67d97d6f 318 ** This prepares the state buffer for the next function call. */
emh203 0:3d9c67d97d6f 319
emh203 0:3d9c67d97d6f 320 /* Points to the start of the state buffer */
emh203 0:3d9c67d97d6f 321 pStateCurnt = S->pState;
emh203 0:3d9c67d97d6f 322
emh203 0:3d9c67d97d6f 323 i = (numTaps - 1u) >> 2u;
emh203 0:3d9c67d97d6f 324
emh203 0:3d9c67d97d6f 325 /* copy data */
emh203 0:3d9c67d97d6f 326 while(i > 0u)
emh203 0:3d9c67d97d6f 327 {
emh203 0:3d9c67d97d6f 328 *pStateCurnt++ = *pState++;
emh203 0:3d9c67d97d6f 329 *pStateCurnt++ = *pState++;
emh203 0:3d9c67d97d6f 330 *pStateCurnt++ = *pState++;
emh203 0:3d9c67d97d6f 331 *pStateCurnt++ = *pState++;
emh203 0:3d9c67d97d6f 332
emh203 0:3d9c67d97d6f 333 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 334 i--;
emh203 0:3d9c67d97d6f 335 }
emh203 0:3d9c67d97d6f 336
emh203 0:3d9c67d97d6f 337 i = (numTaps - 1u) % 0x04u;
emh203 0:3d9c67d97d6f 338
emh203 0:3d9c67d97d6f 339 /* copy data */
emh203 0:3d9c67d97d6f 340 while(i > 0u)
emh203 0:3d9c67d97d6f 341 {
emh203 0:3d9c67d97d6f 342 *pStateCurnt++ = *pState++;
emh203 0:3d9c67d97d6f 343
emh203 0:3d9c67d97d6f 344 /* Decrement the loop counter */
emh203 0:3d9c67d97d6f 345 i--;
emh203 0:3d9c67d97d6f 346 }
emh203 0:3d9c67d97d6f 347 }
emh203 0:3d9c67d97d6f 348
emh203 0:3d9c67d97d6f 349 /**
emh203 0:3d9c67d97d6f 350 * @} end of FIR_decimate group
emh203 0:3d9c67d97d6f 351 */