mbed official / mbed-dsp

CMSIS DSP library

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cmsis_dsp/FilteringFunctions/arm_biquad_cascade_df1_q31.c@3:7a284390b0ce, 2013-11-08 (annotated)

Committer:
mbed_official
Date:
Fri Nov 08 13:45:10 2013 +0000
Revision:
3:7a284390b0ce
Parent:
2:da51fb522205 
Synchronized with git revision e69956aba2f68a2a26ac26b051f8d349deaa1ce8

Who changed what in which revision?

UserRevisionLine numberNew contents of line
emilmont 1:fdd22bb7aa52 1 /* ----------------------------------------------------------------------
mbed_official 3:7a284390b0ce 2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
emilmont 1:fdd22bb7aa52 3 *
mbed_official 3:7a284390b0ce 4 * $Date: 17. January 2013
mbed_official 3:7a284390b0ce 5 * $Revision: V1.4.1
emilmont 1:fdd22bb7aa52 6 *
emilmont 2:da51fb522205 7 * Project: CMSIS DSP Library
emilmont 2:da51fb522205 8 * Title: arm_biquad_cascade_df1_q31.c
emilmont 1:fdd22bb7aa52 9 *
emilmont 2:da51fb522205 10 * Description: Processing function for the
emilmont 2:da51fb522205 11 * Q31 Biquad cascade filter
emilmont 1:fdd22bb7aa52 12 *
emilmont 1:fdd22bb7aa52 13 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
emilmont 1:fdd22bb7aa52 14 *
mbed_official 3:7a284390b0ce 15 * Redistribution and use in source and binary forms, with or without
mbed_official 3:7a284390b0ce 16 * modification, are permitted provided that the following conditions
mbed_official 3:7a284390b0ce 17 * are met:
mbed_official 3:7a284390b0ce 18 * - Redistributions of source code must retain the above copyright
mbed_official 3:7a284390b0ce 19 * notice, this list of conditions and the following disclaimer.
mbed_official 3:7a284390b0ce 20 * - Redistributions in binary form must reproduce the above copyright
mbed_official 3:7a284390b0ce 21 * notice, this list of conditions and the following disclaimer in
mbed_official 3:7a284390b0ce 22 * the documentation and/or other materials provided with the
mbed_official 3:7a284390b0ce 23 * distribution.
mbed_official 3:7a284390b0ce 24 * - Neither the name of ARM LIMITED nor the names of its contributors
mbed_official 3:7a284390b0ce 25 * may be used to endorse or promote products derived from this
mbed_official 3:7a284390b0ce 26 * software without specific prior written permission.
mbed_official 3:7a284390b0ce 27 *
mbed_official 3:7a284390b0ce 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
mbed_official 3:7a284390b0ce 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
mbed_official 3:7a284390b0ce 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
mbed_official 3:7a284390b0ce 31 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
mbed_official 3:7a284390b0ce 32 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
mbed_official 3:7a284390b0ce 33 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
mbed_official 3:7a284390b0ce 34 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
mbed_official 3:7a284390b0ce 35 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
mbed_official 3:7a284390b0ce 36 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
mbed_official 3:7a284390b0ce 37 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
mbed_official 3:7a284390b0ce 38 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
mbed_official 3:7a284390b0ce 39 * POSSIBILITY OF SUCH DAMAGE.
emilmont 1:fdd22bb7aa52 40 * -------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 41
emilmont 1:fdd22bb7aa52 42 #include "arm_math.h"
emilmont 1:fdd22bb7aa52 43
emilmont 1:fdd22bb7aa52 44 /**
emilmont 1:fdd22bb7aa52 45 * @ingroup groupFilters
emilmont 1:fdd22bb7aa52 46 */
emilmont 1:fdd22bb7aa52 47
emilmont 1:fdd22bb7aa52 48 /**
emilmont 1:fdd22bb7aa52 49 * @addtogroup BiquadCascadeDF1
emilmont 1:fdd22bb7aa52 50 * @{
emilmont 1:fdd22bb7aa52 51 */
emilmont 1:fdd22bb7aa52 52
emilmont 1:fdd22bb7aa52 53 /**
emilmont 1:fdd22bb7aa52 54 * @brief Processing function for the Q31 Biquad cascade filter.
emilmont 1:fdd22bb7aa52 55 * @param[in] *S points to an instance of the Q31 Biquad cascade structure.
emilmont 1:fdd22bb7aa52 56 * @param[in] *pSrc points to the block of input data.
emilmont 1:fdd22bb7aa52 57 * @param[out] *pDst points to the block of output data.
emilmont 1:fdd22bb7aa52 58 * @param[in] blockSize number of samples to process per call.
emilmont 1:fdd22bb7aa52 59 * @return none.
emilmont 1:fdd22bb7aa52 60 *
emilmont 1:fdd22bb7aa52 61 * <b>Scaling and Overflow Behavior:</b>
emilmont 1:fdd22bb7aa52 62 * \par
emilmont 1:fdd22bb7aa52 63 * The function is implemented using an internal 64-bit accumulator.
emilmont 1:fdd22bb7aa52 64 * 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 65 * Thus, if the accumulator result overflows it wraps around rather than clip.
emilmont 1:fdd22bb7aa52 66 * In order to avoid overflows completely the input signal must be scaled down by 2 bits and lie in the range [-0.25 +0.25).
emilmont 1:fdd22bb7aa52 67 * After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to
emilmont 1:fdd22bb7aa52 68 * 1.31 format by discarding the low 32 bits.
emilmont 1:fdd22bb7aa52 69 *
emilmont 1:fdd22bb7aa52 70 * \par
emilmont 1:fdd22bb7aa52 71 * Refer to the function <code>arm_biquad_cascade_df1_fast_q31()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
emilmont 1:fdd22bb7aa52 72 */
emilmont 1:fdd22bb7aa52 73
emilmont 1:fdd22bb7aa52 74 void arm_biquad_cascade_df1_q31(
emilmont 1:fdd22bb7aa52 75 const arm_biquad_casd_df1_inst_q31 * S,
emilmont 1:fdd22bb7aa52 76 q31_t * pSrc,
emilmont 1:fdd22bb7aa52 77 q31_t * pDst,
emilmont 1:fdd22bb7aa52 78 uint32_t blockSize)
emilmont 1:fdd22bb7aa52 79 {
emilmont 1:fdd22bb7aa52 80 q63_t acc; /* accumulator */
emilmont 1:fdd22bb7aa52 81 uint32_t uShift = ((uint32_t) S->postShift + 1u);
emilmont 1:fdd22bb7aa52 82 uint32_t lShift = 32u - uShift; /* Shift to be applied to the output */
emilmont 1:fdd22bb7aa52 83 q31_t *pIn = pSrc; /* input pointer initialization */
emilmont 1:fdd22bb7aa52 84 q31_t *pOut = pDst; /* output pointer initialization */
emilmont 1:fdd22bb7aa52 85 q31_t *pState = S->pState; /* pState pointer initialization */
emilmont 1:fdd22bb7aa52 86 q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */
emilmont 1:fdd22bb7aa52 87 q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
emilmont 1:fdd22bb7aa52 88 q31_t b0, b1, b2, a1, a2; /* Filter coefficients */
emilmont 1:fdd22bb7aa52 89 q31_t Xn; /* temporary input */
emilmont 1:fdd22bb7aa52 90 uint32_t sample, stage = S->numStages; /* loop counters */
emilmont 1:fdd22bb7aa52 91
emilmont 1:fdd22bb7aa52 92
mbed_official 3:7a284390b0ce 93 #ifndef ARM_MATH_CM0_FAMILY
emilmont 1:fdd22bb7aa52 94
emilmont 1:fdd22bb7aa52 95 q31_t acc_l, acc_h; /* temporary output variables */
emilmont 1:fdd22bb7aa52 96
emilmont 1:fdd22bb7aa52 97 /* Run the below code for Cortex-M4 and Cortex-M3 */
emilmont 1:fdd22bb7aa52 98
emilmont 1:fdd22bb7aa52 99 do
emilmont 1:fdd22bb7aa52 100 {
emilmont 1:fdd22bb7aa52 101 /* Reading the coefficients */
emilmont 1:fdd22bb7aa52 102 b0 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 103 b1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 104 b2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 105 a1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 106 a2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 107
emilmont 1:fdd22bb7aa52 108 /* Reading the state values */
emilmont 1:fdd22bb7aa52 109 Xn1 = pState[0];
emilmont 1:fdd22bb7aa52 110 Xn2 = pState[1];
emilmont 1:fdd22bb7aa52 111 Yn1 = pState[2];
emilmont 1:fdd22bb7aa52 112 Yn2 = pState[3];
emilmont 1:fdd22bb7aa52 113
emilmont 1:fdd22bb7aa52 114 /* Apply loop unrolling and compute 4 output values simultaneously. */
emilmont 1:fdd22bb7aa52 115 /* The variable acc hold output values that are being computed:
emilmont 1:fdd22bb7aa52 116 *
emilmont 1:fdd22bb7aa52 117 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
emilmont 1:fdd22bb7aa52 118 */
emilmont 1:fdd22bb7aa52 119
emilmont 1:fdd22bb7aa52 120 sample = blockSize >> 2u;
emilmont 1:fdd22bb7aa52 121
emilmont 1:fdd22bb7aa52 122 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
emilmont 1:fdd22bb7aa52 123 ** a second loop below computes the remaining 1 to 3 samples. */
emilmont 1:fdd22bb7aa52 124 while(sample > 0u)
emilmont 1:fdd22bb7aa52 125 {
emilmont 1:fdd22bb7aa52 126 /* Read the input */
emilmont 1:fdd22bb7aa52 127 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 128
emilmont 1:fdd22bb7aa52 129 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 130
emilmont 1:fdd22bb7aa52 131 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 132 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 133 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 134 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 135 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 136 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 137 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 138 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 139 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 140 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 141
emilmont 1:fdd22bb7aa52 142 /* The result is converted to 1.31 , Yn2 variable is reused */
emilmont 1:fdd22bb7aa52 143
emilmont 1:fdd22bb7aa52 144 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 145 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 146
emilmont 1:fdd22bb7aa52 147 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 148 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 149
emilmont 1:fdd22bb7aa52 150 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 151 Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 152
emilmont 1:fdd22bb7aa52 153 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 154 *pOut++ = Yn2;
emilmont 1:fdd22bb7aa52 155
emilmont 1:fdd22bb7aa52 156 /* Read the second input */
emilmont 1:fdd22bb7aa52 157 Xn2 = *pIn++;
emilmont 1:fdd22bb7aa52 158
emilmont 1:fdd22bb7aa52 159 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 160
emilmont 1:fdd22bb7aa52 161 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 162 acc = (q63_t) b0 *Xn2;
emilmont 1:fdd22bb7aa52 163 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 164 acc += (q63_t) b1 *Xn;
emilmont 1:fdd22bb7aa52 165 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 166 acc += (q63_t) b2 *Xn1;
emilmont 1:fdd22bb7aa52 167 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 168 acc += (q63_t) a1 *Yn2;
emilmont 1:fdd22bb7aa52 169 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 170 acc += (q63_t) a2 *Yn1;
emilmont 1:fdd22bb7aa52 171
emilmont 1:fdd22bb7aa52 172
emilmont 1:fdd22bb7aa52 173 /* The result is converted to 1.31, Yn1 variable is reused */
emilmont 1:fdd22bb7aa52 174
emilmont 1:fdd22bb7aa52 175 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 176 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 177
emilmont 1:fdd22bb7aa52 178 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 179 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 180
emilmont 1:fdd22bb7aa52 181
emilmont 1:fdd22bb7aa52 182 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 183 Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 184
emilmont 1:fdd22bb7aa52 185 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 186 *pOut++ = Yn1;
emilmont 1:fdd22bb7aa52 187
emilmont 1:fdd22bb7aa52 188 /* Read the third input */
emilmont 1:fdd22bb7aa52 189 Xn1 = *pIn++;
emilmont 1:fdd22bb7aa52 190
emilmont 1:fdd22bb7aa52 191 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 192
emilmont 1:fdd22bb7aa52 193 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 194 acc = (q63_t) b0 *Xn1;
emilmont 1:fdd22bb7aa52 195 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 196 acc += (q63_t) b1 *Xn2;
emilmont 1:fdd22bb7aa52 197 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 198 acc += (q63_t) b2 *Xn;
emilmont 1:fdd22bb7aa52 199 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 200 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 201 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 202 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 203
emilmont 1:fdd22bb7aa52 204 /* The result is converted to 1.31, Yn2 variable is reused */
emilmont 1:fdd22bb7aa52 205 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 206 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 207
emilmont 1:fdd22bb7aa52 208 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 209 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 210
emilmont 1:fdd22bb7aa52 211
emilmont 1:fdd22bb7aa52 212 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 213 Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 214
emilmont 1:fdd22bb7aa52 215 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 216 *pOut++ = Yn2;
emilmont 1:fdd22bb7aa52 217
emilmont 1:fdd22bb7aa52 218 /* Read the forth input */
emilmont 1:fdd22bb7aa52 219 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 220
emilmont 1:fdd22bb7aa52 221 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 222
emilmont 1:fdd22bb7aa52 223 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 224 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 225 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 226 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 227 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 228 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 229 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 230 acc += (q63_t) a1 *Yn2;
emilmont 1:fdd22bb7aa52 231 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 232 acc += (q63_t) a2 *Yn1;
emilmont 1:fdd22bb7aa52 233
emilmont 1:fdd22bb7aa52 234 /* The result is converted to 1.31, Yn1 variable is reused */
emilmont 1:fdd22bb7aa52 235 /* Calc lower part of acc */
emilmont 1:fdd22bb7aa52 236 acc_l = acc & 0xffffffff;
emilmont 1:fdd22bb7aa52 237
emilmont 1:fdd22bb7aa52 238 /* Calc upper part of acc */
emilmont 1:fdd22bb7aa52 239 acc_h = (acc >> 32) & 0xffffffff;
emilmont 1:fdd22bb7aa52 240
emilmont 1:fdd22bb7aa52 241 /* Apply shift for lower part of acc and upper part of acc */
emilmont 1:fdd22bb7aa52 242 Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
emilmont 1:fdd22bb7aa52 243
emilmont 1:fdd22bb7aa52 244 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 245 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 246 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 247 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 248 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 249 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 250 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 251 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 252
emilmont 1:fdd22bb7aa52 253 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 254 *pOut++ = Yn1;
emilmont 1:fdd22bb7aa52 255
emilmont 1:fdd22bb7aa52 256 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 257 sample--;
emilmont 1:fdd22bb7aa52 258 }
emilmont 1:fdd22bb7aa52 259
emilmont 1:fdd22bb7aa52 260 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
emilmont 1:fdd22bb7aa52 261 ** No loop unrolling is used. */
emilmont 1:fdd22bb7aa52 262 sample = (blockSize & 0x3u);
emilmont 1:fdd22bb7aa52 263
emilmont 1:fdd22bb7aa52 264 while(sample > 0u)
emilmont 1:fdd22bb7aa52 265 {
emilmont 1:fdd22bb7aa52 266 /* Read the input */
emilmont 1:fdd22bb7aa52 267 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 268
emilmont 1:fdd22bb7aa52 269 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 270
emilmont 1:fdd22bb7aa52 271 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 272 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 273 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 274 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 275 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 276 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 277 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 278 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 279 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 280 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 281
emilmont 1:fdd22bb7aa52 282 /* The result is converted to 1.31 */
emilmont 1:fdd22bb7aa52 283 acc = acc >> lShift;
emilmont 1:fdd22bb7aa52 284
emilmont 1:fdd22bb7aa52 285 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 286 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 287 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 288 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 289 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 290 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 291 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 292 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 293 Yn2 = Yn1;
emilmont 1:fdd22bb7aa52 294 Yn1 = (q31_t) acc;
emilmont 1:fdd22bb7aa52 295
emilmont 1:fdd22bb7aa52 296 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 297 *pOut++ = (q31_t) acc;
emilmont 1:fdd22bb7aa52 298
emilmont 1:fdd22bb7aa52 299 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 300 sample--;
emilmont 1:fdd22bb7aa52 301 }
emilmont 1:fdd22bb7aa52 302
emilmont 1:fdd22bb7aa52 303 /* The first stage goes from the input buffer to the output buffer. */
emilmont 1:fdd22bb7aa52 304 /* Subsequent stages occur in-place in the output buffer */
emilmont 1:fdd22bb7aa52 305 pIn = pDst;
emilmont 1:fdd22bb7aa52 306
emilmont 1:fdd22bb7aa52 307 /* Reset to destination pointer */
emilmont 1:fdd22bb7aa52 308 pOut = pDst;
emilmont 1:fdd22bb7aa52 309
emilmont 1:fdd22bb7aa52 310 /* Store the updated state variables back into the pState array */
emilmont 1:fdd22bb7aa52 311 *pState++ = Xn1;
emilmont 1:fdd22bb7aa52 312 *pState++ = Xn2;
emilmont 1:fdd22bb7aa52 313 *pState++ = Yn1;
emilmont 1:fdd22bb7aa52 314 *pState++ = Yn2;
emilmont 1:fdd22bb7aa52 315
emilmont 1:fdd22bb7aa52 316 } while(--stage);
emilmont 1:fdd22bb7aa52 317
emilmont 1:fdd22bb7aa52 318 #else
emilmont 1:fdd22bb7aa52 319
emilmont 1:fdd22bb7aa52 320 /* Run the below code for Cortex-M0 */
emilmont 1:fdd22bb7aa52 321
emilmont 1:fdd22bb7aa52 322 do
emilmont 1:fdd22bb7aa52 323 {
emilmont 1:fdd22bb7aa52 324 /* Reading the coefficients */
emilmont 1:fdd22bb7aa52 325 b0 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 326 b1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 327 b2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 328 a1 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 329 a2 = *pCoeffs++;
emilmont 1:fdd22bb7aa52 330
emilmont 1:fdd22bb7aa52 331 /* Reading the state values */
emilmont 1:fdd22bb7aa52 332 Xn1 = pState[0];
emilmont 1:fdd22bb7aa52 333 Xn2 = pState[1];
emilmont 1:fdd22bb7aa52 334 Yn1 = pState[2];
emilmont 1:fdd22bb7aa52 335 Yn2 = pState[3];
emilmont 1:fdd22bb7aa52 336
emilmont 1:fdd22bb7aa52 337 /* The variables acc holds the output value that is computed:
emilmont 1:fdd22bb7aa52 338 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
emilmont 1:fdd22bb7aa52 339 */
emilmont 1:fdd22bb7aa52 340
emilmont 1:fdd22bb7aa52 341 sample = blockSize;
emilmont 1:fdd22bb7aa52 342
emilmont 1:fdd22bb7aa52 343 while(sample > 0u)
emilmont 1:fdd22bb7aa52 344 {
emilmont 1:fdd22bb7aa52 345 /* Read the input */
emilmont 1:fdd22bb7aa52 346 Xn = *pIn++;
emilmont 1:fdd22bb7aa52 347
emilmont 1:fdd22bb7aa52 348 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 349 /* acc = b0 * x[n] */
emilmont 1:fdd22bb7aa52 350 acc = (q63_t) b0 *Xn;
emilmont 1:fdd22bb7aa52 351
emilmont 1:fdd22bb7aa52 352 /* acc += b1 * x[n-1] */
emilmont 1:fdd22bb7aa52 353 acc += (q63_t) b1 *Xn1;
emilmont 1:fdd22bb7aa52 354 /* acc += b[2] * x[n-2] */
emilmont 1:fdd22bb7aa52 355 acc += (q63_t) b2 *Xn2;
emilmont 1:fdd22bb7aa52 356 /* acc += a1 * y[n-1] */
emilmont 1:fdd22bb7aa52 357 acc += (q63_t) a1 *Yn1;
emilmont 1:fdd22bb7aa52 358 /* acc += a2 * y[n-2] */
emilmont 1:fdd22bb7aa52 359 acc += (q63_t) a2 *Yn2;
emilmont 1:fdd22bb7aa52 360
emilmont 1:fdd22bb7aa52 361 /* The result is converted to 1.31 */
emilmont 1:fdd22bb7aa52 362 acc = acc >> lShift;
emilmont 1:fdd22bb7aa52 363
emilmont 1:fdd22bb7aa52 364 /* Every time after the output is computed state should be updated. */
emilmont 1:fdd22bb7aa52 365 /* The states should be updated as: */
emilmont 1:fdd22bb7aa52 366 /* Xn2 = Xn1 */
emilmont 1:fdd22bb7aa52 367 /* Xn1 = Xn */
emilmont 1:fdd22bb7aa52 368 /* Yn2 = Yn1 */
emilmont 1:fdd22bb7aa52 369 /* Yn1 = acc */
emilmont 1:fdd22bb7aa52 370 Xn2 = Xn1;
emilmont 1:fdd22bb7aa52 371 Xn1 = Xn;
emilmont 1:fdd22bb7aa52 372 Yn2 = Yn1;
emilmont 1:fdd22bb7aa52 373 Yn1 = (q31_t) acc;
emilmont 1:fdd22bb7aa52 374
emilmont 1:fdd22bb7aa52 375 /* Store the output in the destination buffer. */
emilmont 1:fdd22bb7aa52 376 *pOut++ = (q31_t) acc;
emilmont 1:fdd22bb7aa52 377
emilmont 1:fdd22bb7aa52 378 /* decrement the loop counter */
emilmont 1:fdd22bb7aa52 379 sample--;
emilmont 1:fdd22bb7aa52 380 }
emilmont 1:fdd22bb7aa52 381
emilmont 1:fdd22bb7aa52 382 /* The first stage goes from the input buffer to the output buffer. */
emilmont 1:fdd22bb7aa52 383 /* Subsequent stages occur in-place in the output buffer */
emilmont 1:fdd22bb7aa52 384 pIn = pDst;
emilmont 1:fdd22bb7aa52 385
emilmont 1:fdd22bb7aa52 386 /* Reset to destination pointer */
emilmont 1:fdd22bb7aa52 387 pOut = pDst;
emilmont 1:fdd22bb7aa52 388
emilmont 1:fdd22bb7aa52 389 /* Store the updated state variables back into the pState array */
emilmont 1:fdd22bb7aa52 390 *pState++ = Xn1;
emilmont 1:fdd22bb7aa52 391 *pState++ = Xn2;
emilmont 1:fdd22bb7aa52 392 *pState++ = Yn1;
emilmont 1:fdd22bb7aa52 393 *pState++ = Yn2;
emilmont 1:fdd22bb7aa52 394
emilmont 1:fdd22bb7aa52 395 } while(--stage);
emilmont 1:fdd22bb7aa52 396
mbed_official 3:7a284390b0ce 397 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
emilmont 1:fdd22bb7aa52 398 }
emilmont 1:fdd22bb7aa52 399
emilmont 1:fdd22bb7aa52 400 /**
emilmont 1:fdd22bb7aa52 401 * @} end of BiquadCascadeDF1 group
emilmont 1:fdd22bb7aa52 402 */