mbed official / mbed-dsp

CMSIS DSP library

Dependents:   performance_timer Surfboard_ gps2rtty Capstone ... more

Legacy Warning

This is an mbed 2 library. To learn more about mbed OS 5, visit the docs.

cmsis_dsp/FilteringFunctions/arm_fir_decimate_fast_q31.c@1:fdd22bb7aa52, 2012-11-28 (annotated)

Committer:
emilmont
Date:
Wed Nov 28 12:30:09 2012 +0000
Revision:
1:fdd22bb7aa52
Child:
2:da51fb522205
DSP library code

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
emilmont 1:fdd22bb7aa52 2 * Copyright (C) 2010 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
emilmont 1:fdd22bb7aa52 4 * $Date: 15. February 2012
emilmont 1:fdd22bb7aa52 5 * $Revision: V1.1.0
emilmont 1:fdd22bb7aa52 6 *
emilmont 1:fdd22bb7aa52 7 * Project: CMSIS DSP Library
emilmont 1:fdd22bb7aa52 8 * Title: arm_fir_decimate_fast_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 1:fdd22bb7aa52 10 * Description: Fast Q31 FIR Decimator.
emilmont 1:fdd22bb7aa52 11 *
emilmont 1:fdd22bb7aa52 12 * Target Processor: Cortex-M4/Cortex-M3
emilmont 1:fdd22bb7aa52 13 *
emilmont 1:fdd22bb7aa52 14 * Version 1.1.0 2012/02/15
emilmont 1:fdd22bb7aa52 15 * Updated with more optimizations, bug fixes and minor API changes.
emilmont 1:fdd22bb7aa52 16 *
emilmont 1:fdd22bb7aa52 17 * Version 1.0.10 2011/7/15
emilmont 1:fdd22bb7aa52 18 * Big Endian support added and Merged M0 and M3/M4 Source code.
emilmont 1:fdd22bb7aa52 19 *
emilmont 1:fdd22bb7aa52 20 * Version 1.0.3 2010/11/29
emilmont 1:fdd22bb7aa52 21 * Re-organized the CMSIS folders and updated documentation.
emilmont 1:fdd22bb7aa52 22 *
emilmont 1:fdd22bb7aa52 23 * Version 1.0.2 2010/11/11
emilmont 1:fdd22bb7aa52 24 * Documentation updated.
emilmont 1:fdd22bb7aa52 25 *
emilmont 1:fdd22bb7aa52 26 * Version 1.0.1 2010/10/05
emilmont 1:fdd22bb7aa52 27 * Production release and review comments incorporated.
emilmont 1:fdd22bb7aa52 28 *
emilmont 1:fdd22bb7aa52 29 * Version 1.0.0 2010/09/20
emilmont 1:fdd22bb7aa52 30 * Production release and review comments incorporated.
emilmont 1:fdd22bb7aa52 31 * -------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 32
emilmont 1:fdd22bb7aa52 33 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 34
emilmont 1:fdd22bb7aa52 35 /**
emilmont 1:fdd22bb7aa52 36 * @ingroup groupFilters
emilmont 1:fdd22bb7aa52 37 */
emilmont 1:fdd22bb7aa52 38
emilmont 1:fdd22bb7aa52 39 /**
emilmont 1:fdd22bb7aa52 40 * @addtogroup FIR_decimate
emilmont 1:fdd22bb7aa52 41 * @{
emilmont 1:fdd22bb7aa52 42 */
emilmont 1:fdd22bb7aa52 43
emilmont 1:fdd22bb7aa52 44 /**
emilmont 1:fdd22bb7aa52 45 * @brief Processing function for the Q31 FIR decimator (fast variant) for Cortex-M3 and Cortex-M4.
emilmont 1:fdd22bb7aa52 46 * @param[in] *S points to an instance of the Q31 FIR decimator structure.
emilmont 1:fdd22bb7aa52 47 * @param[in] *pSrc points to the block of input data.
emilmont 1:fdd22bb7aa52 48 * @param[out] *pDst points to the block of output data
emilmont 1:fdd22bb7aa52 49 * @param[in] blockSize number of input samples to process per call.
emilmont 1:fdd22bb7aa52 50 * @return none
emilmont 1:fdd22bb7aa52 51 *
emilmont 1:fdd22bb7aa52 52 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 53 *
emilmont 1:fdd22bb7aa52 54 * \par
emilmont 1:fdd22bb7aa52 55 * This function is optimized for speed at the expense of fixed-point precision and overflow protection.
emilmont 1:fdd22bb7aa52 56 * The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format.
emilmont 1:fdd22bb7aa52 57 * These intermediate results are added to a 2.30 accumulator.
emilmont 1:fdd22bb7aa52 58 * Finally, the accumulator is saturated and converted to a 1.31 result.
emilmont 1:fdd22bb7aa52 59 * 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.
emilmont 1:fdd22bb7aa52 60 * 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).
emilmont 1:fdd22bb7aa52 61 *
emilmont 1:fdd22bb7aa52 62 * \par
emilmont 1:fdd22bb7aa52 63 * 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.
emilmont 1:fdd22bb7aa52 64 * Both the slow and the fast versions use the same instance structure.
emilmont 1:fdd22bb7aa52 65 * Use the function <code>arm_fir_decimate_init_q31()</code> to initialize the filter structure.
emilmont 1:fdd22bb7aa52 66 */
emilmont 1:fdd22bb7aa52 67
emilmont 1:fdd22bb7aa52 68 void arm_fir_decimate_fast_q31(
emilmont 1:fdd22bb7aa52 69 arm_fir_decimate_instance_q31 * S,
emilmont 1:fdd22bb7aa52 70 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 71 q31_t * pDst,
emilmont 1:fdd22bb7aa52 72 uint32_t blockSize)
emilmont 1:fdd22bb7aa52 73 {
emilmont 1:fdd22bb7aa52 74 q31_t *pState = S->pState; /* State pointer */
emilmont 1:fdd22bb7aa52 75 q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */
emilmont 1:fdd22bb7aa52 76 q31_t *pStateCurnt; /* Points to the current sample of the state */
emilmont 1:fdd22bb7aa52 77 q31_t x0, c0; /* Temporary variables to hold state and coefficient values */
emilmont 1:fdd22bb7aa52 78 q31_t *px; /* Temporary pointers for state buffer */
emilmont 1:fdd22bb7aa52 79 q31_t *pb; /* Temporary pointers for coefficient buffer */
emilmont 1:fdd22bb7aa52 80 q31_t sum0; /* Accumulator */
emilmont 1:fdd22bb7aa52 81 uint32_t numTaps = S->numTaps; /* Number of taps */
emilmont 1:fdd22bb7aa52 82 uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */
emilmont 1:fdd22bb7aa52 83 uint32_t blkCntN2;
emilmont 1:fdd22bb7aa52 84 q31_t x1;
emilmont 1:fdd22bb7aa52 85 q31_t acc0, acc1;
emilmont 1:fdd22bb7aa52 86 q31_t *px0, *px1;
emilmont 1:fdd22bb7aa52 87
emilmont 1:fdd22bb7aa52 88 /* S->pState buffer contains previous frame (numTaps - 1) samples */
emilmont 1:fdd22bb7aa52 89 /* pStateCurnt points to the location where the new input data should be written */
emilmont 1:fdd22bb7aa52 90 pStateCurnt = S->pState + (numTaps - 1u);
emilmont 1:fdd22bb7aa52 91
emilmont 1:fdd22bb7aa52 92 /* Total number of output samples to be computed */
emilmont 1:fdd22bb7aa52 93
emilmont 1:fdd22bb7aa52 94 blkCnt = outBlockSize / 2;
emilmont 1:fdd22bb7aa52 95 blkCntN2 = outBlockSize - (2 * blkCnt);
emilmont 1:fdd22bb7aa52 96
emilmont 1:fdd22bb7aa52 97 while(blkCnt > 0u)
emilmont 1:fdd22bb7aa52 98 {
emilmont 1:fdd22bb7aa52 99 /* Copy decimation factor number of new input samples into the state buffer */
emilmont 1:fdd22bb7aa52 100 i = 2 * S->M;
emilmont 1:fdd22bb7aa52 101
emilmont 1:fdd22bb7aa52 102 do
emilmont 1:fdd22bb7aa52 103 {
emilmont 1:fdd22bb7aa52 104 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 105
emilmont 1:fdd22bb7aa52 106 } while(--i);
emilmont 1:fdd22bb7aa52 107
emilmont 1:fdd22bb7aa52 108 /* Set accumulator to zero */
emilmont 1:fdd22bb7aa52 109 acc0 = 0;
emilmont 1:fdd22bb7aa52 110 acc1 = 0;
emilmont 1:fdd22bb7aa52 111
emilmont 1:fdd22bb7aa52 112 /* Initialize state pointer */
emilmont 1:fdd22bb7aa52 113 px0 = pState;
emilmont 1:fdd22bb7aa52 114 px1 = pState + S->M;
emilmont 1:fdd22bb7aa52 115
emilmont 1:fdd22bb7aa52 116 /* Initialize coeff pointer */
emilmont 1:fdd22bb7aa52 117 pb = pCoeffs;
emilmont 1:fdd22bb7aa52 118
emilmont 1:fdd22bb7aa52 119 /* Loop unrolling. Process 4 taps at a time. */
emilmont 1:fdd22bb7aa52 120 tapCnt = numTaps >> 2;
emilmont 1:fdd22bb7aa52 121
emilmont 1:fdd22bb7aa52 122 /* Loop over the number of taps. Unroll by a factor of 4.
emilmont 1:fdd22bb7aa52 123 ** Repeat until we've computed numTaps-4 coefficients. */
emilmont 1:fdd22bb7aa52 124 while(tapCnt > 0u)
emilmont 1:fdd22bb7aa52 125 {
emilmont 1:fdd22bb7aa52 126 /* Read the b[numTaps-1] coefficient */
emilmont 1:fdd22bb7aa52 127 c0 = *(pb);
emilmont 1:fdd22bb7aa52 128
emilmont 1:fdd22bb7aa52 129 /* Read x[n-numTaps-1] for sample 0 sample 1 */
emilmont 1:fdd22bb7aa52 130 x0 = *(px0);
emilmont 1:fdd22bb7aa52 131 x1 = *(px1);
emilmont 1:fdd22bb7aa52 132
emilmont 1:fdd22bb7aa52 133 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 134 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 135 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 136
emilmont 1:fdd22bb7aa52 137 /* Read the b[numTaps-2] coefficient */
emilmont 1:fdd22bb7aa52 138 c0 = *(pb + 1u);
emilmont 1:fdd22bb7aa52 139
emilmont 1:fdd22bb7aa52 140 /* Read x[n-numTaps-2] for sample 0 sample 1 */
emilmont 1:fdd22bb7aa52 141 x0 = *(px0 + 1u);
emilmont 1:fdd22bb7aa52 142 x1 = *(px1 + 1u);
emilmont 1:fdd22bb7aa52 143
emilmont 1:fdd22bb7aa52 144 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 145 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 146 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 147
emilmont 1:fdd22bb7aa52 148 /* Read the b[numTaps-3] coefficient */
emilmont 1:fdd22bb7aa52 149 c0 = *(pb + 2u);
emilmont 1:fdd22bb7aa52 150
emilmont 1:fdd22bb7aa52 151 /* Read x[n-numTaps-3] for sample 0 sample 1 */
emilmont 1:fdd22bb7aa52 152 x0 = *(px0 + 2u);
emilmont 1:fdd22bb7aa52 153 x1 = *(px1 + 2u);
emilmont 1:fdd22bb7aa52 154 pb += 4u;
emilmont 1:fdd22bb7aa52 155
emilmont 1:fdd22bb7aa52 156 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 157 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 158 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 159
emilmont 1:fdd22bb7aa52 160 /* Read the b[numTaps-4] coefficient */
emilmont 1:fdd22bb7aa52 161 c0 = *(pb - 1u);
emilmont 1:fdd22bb7aa52 162
emilmont 1:fdd22bb7aa52 163 /* Read x[n-numTaps-4] for sample 0 sample 1 */
emilmont 1:fdd22bb7aa52 164 x0 = *(px0 + 3u);
emilmont 1:fdd22bb7aa52 165 x1 = *(px1 + 3u);
emilmont 1:fdd22bb7aa52 166
emilmont 1:fdd22bb7aa52 167
emilmont 1:fdd22bb7aa52 168 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 169 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 170 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 171
emilmont 1:fdd22bb7aa52 172 /* update state pointers */
emilmont 1:fdd22bb7aa52 173 px0 += 4u;
emilmont 1:fdd22bb7aa52 174 px1 += 4u;
emilmont 1:fdd22bb7aa52 175
emilmont 1:fdd22bb7aa52 176 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 177 tapCnt--;
emilmont 1:fdd22bb7aa52 178 }
emilmont 1:fdd22bb7aa52 179
emilmont 1:fdd22bb7aa52 180 /* If the filter length is not a multiple of 4, compute the remaining filter taps */
emilmont 1:fdd22bb7aa52 181 tapCnt = numTaps % 0x4u;
emilmont 1:fdd22bb7aa52 182
emilmont 1:fdd22bb7aa52 183 while(tapCnt > 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 x0 = *(px0++);
emilmont 1:fdd22bb7aa52 190 x1 = *(px1++);
emilmont 1:fdd22bb7aa52 191
emilmont 1:fdd22bb7aa52 192 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 193 acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 194 acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 195
emilmont 1:fdd22bb7aa52 196 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 197 tapCnt--;
emilmont 1:fdd22bb7aa52 198 }
emilmont 1:fdd22bb7aa52 199
emilmont 1:fdd22bb7aa52 200 /* Advance the state pointer by the decimation factor
emilmont 1:fdd22bb7aa52 201 * to process the next group of decimation factor number samples */
emilmont 1:fdd22bb7aa52 202 pState = pState + S->M * 2;
emilmont 1:fdd22bb7aa52 203
emilmont 1:fdd22bb7aa52 204 /* The result is in the accumulator, store in the destination buffer. */
emilmont 1:fdd22bb7aa52 205 *pDst++ = (q31_t) (acc0 << 1);
emilmont 1:fdd22bb7aa52 206 *pDst++ = (q31_t) (acc1 << 1);
emilmont 1:fdd22bb7aa52 207
emilmont 1:fdd22bb7aa52 208 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 209 blkCnt--;
emilmont 1:fdd22bb7aa52 210 }
emilmont 1:fdd22bb7aa52 211
emilmont 1:fdd22bb7aa52 212 while(blkCntN2 > 0u)
emilmont 1:fdd22bb7aa52 213 {
emilmont 1:fdd22bb7aa52 214 /* Copy decimation factor number of new input samples into the state buffer */
emilmont 1:fdd22bb7aa52 215 i = S->M;
emilmont 1:fdd22bb7aa52 216
emilmont 1:fdd22bb7aa52 217 do
emilmont 1:fdd22bb7aa52 218 {
emilmont 1:fdd22bb7aa52 219 *pStateCurnt++ = *pSrc++;
emilmont 1:fdd22bb7aa52 220
emilmont 1:fdd22bb7aa52 221 } while(--i);
emilmont 1:fdd22bb7aa52 222
emilmont 1:fdd22bb7aa52 223 /* Set accumulator to zero */
emilmont 1:fdd22bb7aa52 224 sum0 = 0;
emilmont 1:fdd22bb7aa52 225
emilmont 1:fdd22bb7aa52 226 /* Initialize state pointer */
emilmont 1:fdd22bb7aa52 227 px = pState;
emilmont 1:fdd22bb7aa52 228
emilmont 1:fdd22bb7aa52 229 /* Initialize coeff pointer */
emilmont 1:fdd22bb7aa52 230 pb = pCoeffs;
emilmont 1:fdd22bb7aa52 231
emilmont 1:fdd22bb7aa52 232 /* Loop unrolling. Process 4 taps at a time. */
emilmont 1:fdd22bb7aa52 233 tapCnt = numTaps >> 2;
emilmont 1:fdd22bb7aa52 234
emilmont 1:fdd22bb7aa52 235 /* Loop over the number of taps. Unroll by a factor of 4.
emilmont 1:fdd22bb7aa52 236 ** Repeat until we've computed numTaps-4 coefficients. */
emilmont 1:fdd22bb7aa52 237 while(tapCnt > 0u)
emilmont 1:fdd22bb7aa52 238 {
emilmont 1:fdd22bb7aa52 239 /* Read the b[numTaps-1] coefficient */
emilmont 1:fdd22bb7aa52 240 c0 = *(pb++);
emilmont 1:fdd22bb7aa52 241
emilmont 1:fdd22bb7aa52 242 /* Read x[n-numTaps-1] sample */
emilmont 1:fdd22bb7aa52 243 x0 = *(px++);
emilmont 1:fdd22bb7aa52 244
emilmont 1:fdd22bb7aa52 245 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 246 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 247
emilmont 1:fdd22bb7aa52 248 /* Read the b[numTaps-2] coefficient */
emilmont 1:fdd22bb7aa52 249 c0 = *(pb++);
emilmont 1:fdd22bb7aa52 250
emilmont 1:fdd22bb7aa52 251 /* Read x[n-numTaps-2] sample */
emilmont 1:fdd22bb7aa52 252 x0 = *(px++);
emilmont 1:fdd22bb7aa52 253
emilmont 1:fdd22bb7aa52 254 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 255 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 256
emilmont 1:fdd22bb7aa52 257 /* Read the b[numTaps-3] coefficient */
emilmont 1:fdd22bb7aa52 258 c0 = *(pb++);
emilmont 1:fdd22bb7aa52 259
emilmont 1:fdd22bb7aa52 260 /* Read x[n-numTaps-3] sample */
emilmont 1:fdd22bb7aa52 261 x0 = *(px++);
emilmont 1:fdd22bb7aa52 262
emilmont 1:fdd22bb7aa52 263 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 264 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 265
emilmont 1:fdd22bb7aa52 266 /* Read the b[numTaps-4] coefficient */
emilmont 1:fdd22bb7aa52 267 c0 = *(pb++);
emilmont 1:fdd22bb7aa52 268
emilmont 1:fdd22bb7aa52 269 /* Read x[n-numTaps-4] sample */
emilmont 1:fdd22bb7aa52 270 x0 = *(px++);
emilmont 1:fdd22bb7aa52 271
emilmont 1:fdd22bb7aa52 272 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 273 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 274
emilmont 1:fdd22bb7aa52 275 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 276 tapCnt--;
emilmont 1:fdd22bb7aa52 277 }
emilmont 1:fdd22bb7aa52 278
emilmont 1:fdd22bb7aa52 279 /* If the filter length is not a multiple of 4, compute the remaining filter taps */
emilmont 1:fdd22bb7aa52 280 tapCnt = numTaps % 0x4u;
emilmont 1:fdd22bb7aa52 281
emilmont 1:fdd22bb7aa52 282 while(tapCnt > 0u)
emilmont 1:fdd22bb7aa52 283 {
emilmont 1:fdd22bb7aa52 284 /* Read coefficients */
emilmont 1:fdd22bb7aa52 285 c0 = *(pb++);
emilmont 1:fdd22bb7aa52 286
emilmont 1:fdd22bb7aa52 287 /* Fetch 1 state variable */
emilmont 1:fdd22bb7aa52 288 x0 = *(px++);
emilmont 1:fdd22bb7aa52 289
emilmont 1:fdd22bb7aa52 290 /* Perform the multiply-accumulate */
emilmont 1:fdd22bb7aa52 291 sum0 = (q31_t) ((((q63_t) sum0 << 32) + ((q63_t) x0 * c0)) >> 32);
emilmont 1:fdd22bb7aa52 292
emilmont 1:fdd22bb7aa52 293 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 294 tapCnt--;
emilmont 1:fdd22bb7aa52 295 }
emilmont 1:fdd22bb7aa52 296
emilmont 1:fdd22bb7aa52 297 /* Advance the state pointer by the decimation factor
emilmont 1:fdd22bb7aa52 298 * to process the next group of decimation factor number samples */
emilmont 1:fdd22bb7aa52 299 pState = pState + S->M;
emilmont 1:fdd22bb7aa52 300
emilmont 1:fdd22bb7aa52 301 /* The result is in the accumulator, store in the destination buffer. */
emilmont 1:fdd22bb7aa52 302 *pDst++ = (q31_t) (sum0 << 1);
emilmont 1:fdd22bb7aa52 303
emilmont 1:fdd22bb7aa52 304 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 305 blkCntN2--;
emilmont 1:fdd22bb7aa52 306 }
emilmont 1:fdd22bb7aa52 307
emilmont 1:fdd22bb7aa52 308 /* Processing is complete.
emilmont 1:fdd22bb7aa52 309 ** Now copy the last numTaps - 1 samples to the satrt of the state buffer.
emilmont 1:fdd22bb7aa52 310 ** This prepares the state buffer for the next function call. */
emilmont 1:fdd22bb7aa52 311
emilmont 1:fdd22bb7aa52 312 /* Points to the start of the state buffer */
emilmont 1:fdd22bb7aa52 313 pStateCurnt = S->pState;
emilmont 1:fdd22bb7aa52 314
emilmont 1:fdd22bb7aa52 315 i = (numTaps - 1u) >> 2u;
emilmont 1:fdd22bb7aa52 316
emilmont 1:fdd22bb7aa52 317 /* copy data */
emilmont 1:fdd22bb7aa52 318 while(i > 0u)
emilmont 1:fdd22bb7aa52 319 {
emilmont 1:fdd22bb7aa52 320 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 321 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 322 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 323 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 324
emilmont 1:fdd22bb7aa52 325 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 326 i--;
emilmont 1:fdd22bb7aa52 327 }
emilmont 1:fdd22bb7aa52 328
emilmont 1:fdd22bb7aa52 329 i = (numTaps - 1u) % 0x04u;
emilmont 1:fdd22bb7aa52 330
emilmont 1:fdd22bb7aa52 331 /* copy data */
emilmont 1:fdd22bb7aa52 332 while(i > 0u)
emilmont 1:fdd22bb7aa52 333 {
emilmont 1:fdd22bb7aa52 334 *pStateCurnt++ = *pState++;
emilmont 1:fdd22bb7aa52 335
emilmont 1:fdd22bb7aa52 336 /* Decrement the loop counter */
emilmont 1:fdd22bb7aa52 337 i--;
emilmont 1:fdd22bb7aa52 338 }
emilmont 1:fdd22bb7aa52 339 }
emilmont 1:fdd22bb7aa52 340
emilmont 1:fdd22bb7aa52 341 /**
emilmont 1:fdd22bb7aa52 342 * @} end of FIR_decimate group
emilmont 1:fdd22bb7aa52 343 */