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The CMSIS DSP 5 library

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functions/FilteringFunctions/arm_biquad_cascade_df1_q31.c@3:4098b9d3d571, 2018-06-21 (annotated)

Committer:
xorjoep
Date:
Thu Jun 21 11:56:27 2018 +0000
Revision:
3:4098b9d3d571
Parent:
1:24714b45cd1b 
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xorjoep 1:24714b45cd1b 1 /* ----------------------------------------------------------------------
xorjoep 1:24714b45cd1b 2 * Project: CMSIS DSP Library
xorjoep 1:24714b45cd1b 3 * Title: arm_biquad_cascade_df1_q31.c
xorjoep 1:24714b45cd1b 4 * Description: Processing function for the Q31 Biquad cascade filter
xorjoep 1:24714b45cd1b 5 *
xorjoep 1:24714b45cd1b 6 * $Date: 27. January 2017
xorjoep 1:24714b45cd1b 7 * $Revision: V.1.5.1
xorjoep 1:24714b45cd1b 8 *
xorjoep 1:24714b45cd1b 9 * Target Processor: Cortex-M cores
xorjoep 1:24714b45cd1b 10 * -------------------------------------------------------------------- */
xorjoep 1:24714b45cd1b 11 /*
xorjoep 1:24714b45cd1b 12 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
xorjoep 1:24714b45cd1b 13 *
xorjoep 1:24714b45cd1b 14 * SPDX-License-Identifier: Apache-2.0
xorjoep 1:24714b45cd1b 15 *
xorjoep 1:24714b45cd1b 16 * Licensed under the Apache License, Version 2.0 (the License); you may
xorjoep 1:24714b45cd1b 17 * not use this file except in compliance with the License.
xorjoep 1:24714b45cd1b 18 * You may obtain a copy of the License at
xorjoep 1:24714b45cd1b 19 *
xorjoep 1:24714b45cd1b 20 * www.apache.org/licenses/LICENSE-2.0
xorjoep 1:24714b45cd1b 21 *
xorjoep 1:24714b45cd1b 22 * Unless required by applicable law or agreed to in writing, software
xorjoep 1:24714b45cd1b 23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
xorjoep 1:24714b45cd1b 24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
xorjoep 1:24714b45cd1b 25 * See the License for the specific language governing permissions and
xorjoep 1:24714b45cd1b 26 * limitations under the License.
xorjoep 1:24714b45cd1b 27 */
xorjoep 1:24714b45cd1b 28
xorjoep 1:24714b45cd1b 29 #include "arm_math.h"
xorjoep 1:24714b45cd1b 30
xorjoep 1:24714b45cd1b 31 /**
xorjoep 1:24714b45cd1b 32 * @ingroup groupFilters
xorjoep 1:24714b45cd1b 33 */
xorjoep 1:24714b45cd1b 34
xorjoep 1:24714b45cd1b 35 /**
xorjoep 1:24714b45cd1b 36 * @addtogroup BiquadCascadeDF1
xorjoep 1:24714b45cd1b 37 * @{
xorjoep 1:24714b45cd1b 38 */
xorjoep 1:24714b45cd1b 39
xorjoep 1:24714b45cd1b 40 /**
xorjoep 1:24714b45cd1b 41 * @brief Processing function for the Q31 Biquad cascade filter.
xorjoep 1:24714b45cd1b 42 * @param[in] *S points to an instance of the Q31 Biquad cascade structure.
xorjoep 1:24714b45cd1b 43 * @param[in] *pSrc points to the block of input data.
xorjoep 1:24714b45cd1b 44 * @param[out] *pDst points to the block of output data.
xorjoep 1:24714b45cd1b 45 * @param[in] blockSize number of samples to process per call.
xorjoep 1:24714b45cd1b 46 * @return none.
xorjoep 1:24714b45cd1b 47 *
xorjoep 1:24714b45cd1b 48 * <b>Scaling and Overflow Behavior:</b>
xorjoep 1:24714b45cd1b 49 * \par
xorjoep 1:24714b45cd1b 50 * The function is implemented using an internal 64-bit accumulator.
xorjoep 1:24714b45cd1b 51 * The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit.
xorjoep 1:24714b45cd1b 52 * Thus, if the accumulator result overflows it wraps around rather than clip.
xorjoep 1:24714b45cd1b 53 * 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).
xorjoep 1:24714b45cd1b 54 * After all 5 multiply-accumulates are performed, the 2.62 accumulator is shifted by <code>postShift</code> bits and the result truncated to
xorjoep 1:24714b45cd1b 55 * 1.31 format by discarding the low 32 bits.
xorjoep 1:24714b45cd1b 56 *
xorjoep 1:24714b45cd1b 57 * \par
xorjoep 1:24714b45cd1b 58 * 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.
xorjoep 1:24714b45cd1b 59 */
xorjoep 1:24714b45cd1b 60
xorjoep 1:24714b45cd1b 61 void arm_biquad_cascade_df1_q31(
xorjoep 1:24714b45cd1b 62 const arm_biquad_casd_df1_inst_q31 * S,
xorjoep 1:24714b45cd1b 63 q31_t * pSrc,
xorjoep 1:24714b45cd1b 64 q31_t * pDst,
xorjoep 1:24714b45cd1b 65 uint32_t blockSize)
xorjoep 1:24714b45cd1b 66 {
xorjoep 1:24714b45cd1b 67 q63_t acc; /* accumulator */
xorjoep 1:24714b45cd1b 68 uint32_t uShift = ((uint32_t) S->postShift + 1U);
xorjoep 1:24714b45cd1b 69 uint32_t lShift = 32U - uShift; /* Shift to be applied to the output */
xorjoep 1:24714b45cd1b 70 q31_t *pIn = pSrc; /* input pointer initialization */
xorjoep 1:24714b45cd1b 71 q31_t *pOut = pDst; /* output pointer initialization */
xorjoep 1:24714b45cd1b 72 q31_t *pState = S->pState; /* pState pointer initialization */
xorjoep 1:24714b45cd1b 73 q31_t *pCoeffs = S->pCoeffs; /* coeff pointer initialization */
xorjoep 1:24714b45cd1b 74 q31_t Xn1, Xn2, Yn1, Yn2; /* Filter state variables */
xorjoep 1:24714b45cd1b 75 q31_t b0, b1, b2, a1, a2; /* Filter coefficients */
xorjoep 1:24714b45cd1b 76 q31_t Xn; /* temporary input */
xorjoep 1:24714b45cd1b 77 uint32_t sample, stage = S->numStages; /* loop counters */
xorjoep 1:24714b45cd1b 78
xorjoep 1:24714b45cd1b 79
xorjoep 1:24714b45cd1b 80 #if defined (ARM_MATH_DSP)
xorjoep 1:24714b45cd1b 81
xorjoep 1:24714b45cd1b 82 q31_t acc_l, acc_h; /* temporary output variables */
xorjoep 1:24714b45cd1b 83
xorjoep 1:24714b45cd1b 84 /* Run the below code for Cortex-M4 and Cortex-M3 */
xorjoep 1:24714b45cd1b 85
xorjoep 1:24714b45cd1b 86 do
xorjoep 1:24714b45cd1b 87 {
xorjoep 1:24714b45cd1b 88 /* Reading the coefficients */
xorjoep 1:24714b45cd1b 89 b0 = *pCoeffs++;
xorjoep 1:24714b45cd1b 90 b1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 91 b2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 92 a1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 93 a2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 94
xorjoep 1:24714b45cd1b 95 /* Reading the state values */
xorjoep 1:24714b45cd1b 96 Xn1 = pState[0];
xorjoep 1:24714b45cd1b 97 Xn2 = pState[1];
xorjoep 1:24714b45cd1b 98 Yn1 = pState[2];
xorjoep 1:24714b45cd1b 99 Yn2 = pState[3];
xorjoep 1:24714b45cd1b 100
xorjoep 1:24714b45cd1b 101 /* Apply loop unrolling and compute 4 output values simultaneously. */
xorjoep 1:24714b45cd1b 102 /* The variable acc hold output values that are being computed:
xorjoep 1:24714b45cd1b 103 *
xorjoep 1:24714b45cd1b 104 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 105 */
xorjoep 1:24714b45cd1b 106
xorjoep 1:24714b45cd1b 107 sample = blockSize >> 2U;
xorjoep 1:24714b45cd1b 108
xorjoep 1:24714b45cd1b 109 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
xorjoep 1:24714b45cd1b 110 ** a second loop below computes the remaining 1 to 3 samples. */
xorjoep 1:24714b45cd1b 111 while (sample > 0U)
xorjoep 1:24714b45cd1b 112 {
xorjoep 1:24714b45cd1b 113 /* Read the input */
xorjoep 1:24714b45cd1b 114 Xn = *pIn++;
xorjoep 1:24714b45cd1b 115
xorjoep 1:24714b45cd1b 116 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 117
xorjoep 1:24714b45cd1b 118 /* acc = b0 * x[n] */
xorjoep 1:24714b45cd1b 119 acc = (q63_t) b0 *Xn;
xorjoep 1:24714b45cd1b 120 /* acc += b1 * x[n-1] */
xorjoep 1:24714b45cd1b 121 acc += (q63_t) b1 *Xn1;
xorjoep 1:24714b45cd1b 122 /* acc += b[2] * x[n-2] */
xorjoep 1:24714b45cd1b 123 acc += (q63_t) b2 *Xn2;
xorjoep 1:24714b45cd1b 124 /* acc += a1 * y[n-1] */
xorjoep 1:24714b45cd1b 125 acc += (q63_t) a1 *Yn1;
xorjoep 1:24714b45cd1b 126 /* acc += a2 * y[n-2] */
xorjoep 1:24714b45cd1b 127 acc += (q63_t) a2 *Yn2;
xorjoep 1:24714b45cd1b 128
xorjoep 1:24714b45cd1b 129 /* The result is converted to 1.31 , Yn2 variable is reused */
xorjoep 1:24714b45cd1b 130
xorjoep 1:24714b45cd1b 131 /* Calc lower part of acc */
xorjoep 1:24714b45cd1b 132 acc_l = acc & 0xffffffff;
xorjoep 1:24714b45cd1b 133
xorjoep 1:24714b45cd1b 134 /* Calc upper part of acc */
xorjoep 1:24714b45cd1b 135 acc_h = (acc >> 32) & 0xffffffff;
xorjoep 1:24714b45cd1b 136
xorjoep 1:24714b45cd1b 137 /* Apply shift for lower part of acc and upper part of acc */
xorjoep 1:24714b45cd1b 138 Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
xorjoep 1:24714b45cd1b 139
xorjoep 1:24714b45cd1b 140 /* Store the output in the destination buffer. */
xorjoep 1:24714b45cd1b 141 *pOut++ = Yn2;
xorjoep 1:24714b45cd1b 142
xorjoep 1:24714b45cd1b 143 /* Read the second input */
xorjoep 1:24714b45cd1b 144 Xn2 = *pIn++;
xorjoep 1:24714b45cd1b 145
xorjoep 1:24714b45cd1b 146 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 147
xorjoep 1:24714b45cd1b 148 /* acc = b0 * x[n] */
xorjoep 1:24714b45cd1b 149 acc = (q63_t) b0 *Xn2;
xorjoep 1:24714b45cd1b 150 /* acc += b1 * x[n-1] */
xorjoep 1:24714b45cd1b 151 acc += (q63_t) b1 *Xn;
xorjoep 1:24714b45cd1b 152 /* acc += b[2] * x[n-2] */
xorjoep 1:24714b45cd1b 153 acc += (q63_t) b2 *Xn1;
xorjoep 1:24714b45cd1b 154 /* acc += a1 * y[n-1] */
xorjoep 1:24714b45cd1b 155 acc += (q63_t) a1 *Yn2;
xorjoep 1:24714b45cd1b 156 /* acc += a2 * y[n-2] */
xorjoep 1:24714b45cd1b 157 acc += (q63_t) a2 *Yn1;
xorjoep 1:24714b45cd1b 158
xorjoep 1:24714b45cd1b 159
xorjoep 1:24714b45cd1b 160 /* The result is converted to 1.31, Yn1 variable is reused */
xorjoep 1:24714b45cd1b 161
xorjoep 1:24714b45cd1b 162 /* Calc lower part of acc */
xorjoep 1:24714b45cd1b 163 acc_l = acc & 0xffffffff;
xorjoep 1:24714b45cd1b 164
xorjoep 1:24714b45cd1b 165 /* Calc upper part of acc */
xorjoep 1:24714b45cd1b 166 acc_h = (acc >> 32) & 0xffffffff;
xorjoep 1:24714b45cd1b 167
xorjoep 1:24714b45cd1b 168
xorjoep 1:24714b45cd1b 169 /* Apply shift for lower part of acc and upper part of acc */
xorjoep 1:24714b45cd1b 170 Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
xorjoep 1:24714b45cd1b 171
xorjoep 1:24714b45cd1b 172 /* Store the output in the destination buffer. */
xorjoep 1:24714b45cd1b 173 *pOut++ = Yn1;
xorjoep 1:24714b45cd1b 174
xorjoep 1:24714b45cd1b 175 /* Read the third input */
xorjoep 1:24714b45cd1b 176 Xn1 = *pIn++;
xorjoep 1:24714b45cd1b 177
xorjoep 1:24714b45cd1b 178 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 179
xorjoep 1:24714b45cd1b 180 /* acc = b0 * x[n] */
xorjoep 1:24714b45cd1b 181 acc = (q63_t) b0 *Xn1;
xorjoep 1:24714b45cd1b 182 /* acc += b1 * x[n-1] */
xorjoep 1:24714b45cd1b 183 acc += (q63_t) b1 *Xn2;
xorjoep 1:24714b45cd1b 184 /* acc += b[2] * x[n-2] */
xorjoep 1:24714b45cd1b 185 acc += (q63_t) b2 *Xn;
xorjoep 1:24714b45cd1b 186 /* acc += a1 * y[n-1] */
xorjoep 1:24714b45cd1b 187 acc += (q63_t) a1 *Yn1;
xorjoep 1:24714b45cd1b 188 /* acc += a2 * y[n-2] */
xorjoep 1:24714b45cd1b 189 acc += (q63_t) a2 *Yn2;
xorjoep 1:24714b45cd1b 190
xorjoep 1:24714b45cd1b 191 /* The result is converted to 1.31, Yn2 variable is reused */
xorjoep 1:24714b45cd1b 192 /* Calc lower part of acc */
xorjoep 1:24714b45cd1b 193 acc_l = acc & 0xffffffff;
xorjoep 1:24714b45cd1b 194
xorjoep 1:24714b45cd1b 195 /* Calc upper part of acc */
xorjoep 1:24714b45cd1b 196 acc_h = (acc >> 32) & 0xffffffff;
xorjoep 1:24714b45cd1b 197
xorjoep 1:24714b45cd1b 198
xorjoep 1:24714b45cd1b 199 /* Apply shift for lower part of acc and upper part of acc */
xorjoep 1:24714b45cd1b 200 Yn2 = (uint32_t) acc_l >> lShift | acc_h << uShift;
xorjoep 1:24714b45cd1b 201
xorjoep 1:24714b45cd1b 202 /* Store the output in the destination buffer. */
xorjoep 1:24714b45cd1b 203 *pOut++ = Yn2;
xorjoep 1:24714b45cd1b 204
xorjoep 1:24714b45cd1b 205 /* Read the forth input */
xorjoep 1:24714b45cd1b 206 Xn = *pIn++;
xorjoep 1:24714b45cd1b 207
xorjoep 1:24714b45cd1b 208 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 209
xorjoep 1:24714b45cd1b 210 /* acc = b0 * x[n] */
xorjoep 1:24714b45cd1b 211 acc = (q63_t) b0 *Xn;
xorjoep 1:24714b45cd1b 212 /* acc += b1 * x[n-1] */
xorjoep 1:24714b45cd1b 213 acc += (q63_t) b1 *Xn1;
xorjoep 1:24714b45cd1b 214 /* acc += b[2] * x[n-2] */
xorjoep 1:24714b45cd1b 215 acc += (q63_t) b2 *Xn2;
xorjoep 1:24714b45cd1b 216 /* acc += a1 * y[n-1] */
xorjoep 1:24714b45cd1b 217 acc += (q63_t) a1 *Yn2;
xorjoep 1:24714b45cd1b 218 /* acc += a2 * y[n-2] */
xorjoep 1:24714b45cd1b 219 acc += (q63_t) a2 *Yn1;
xorjoep 1:24714b45cd1b 220
xorjoep 1:24714b45cd1b 221 /* The result is converted to 1.31, Yn1 variable is reused */
xorjoep 1:24714b45cd1b 222 /* Calc lower part of acc */
xorjoep 1:24714b45cd1b 223 acc_l = acc & 0xffffffff;
xorjoep 1:24714b45cd1b 224
xorjoep 1:24714b45cd1b 225 /* Calc upper part of acc */
xorjoep 1:24714b45cd1b 226 acc_h = (acc >> 32) & 0xffffffff;
xorjoep 1:24714b45cd1b 227
xorjoep 1:24714b45cd1b 228 /* Apply shift for lower part of acc and upper part of acc */
xorjoep 1:24714b45cd1b 229 Yn1 = (uint32_t) acc_l >> lShift | acc_h << uShift;
xorjoep 1:24714b45cd1b 230
xorjoep 1:24714b45cd1b 231 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 232 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 233 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 234 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 235 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 236 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 237 Xn2 = Xn1;
xorjoep 1:24714b45cd1b 238 Xn1 = Xn;
xorjoep 1:24714b45cd1b 239
xorjoep 1:24714b45cd1b 240 /* Store the output in the destination buffer. */
xorjoep 1:24714b45cd1b 241 *pOut++ = Yn1;
xorjoep 1:24714b45cd1b 242
xorjoep 1:24714b45cd1b 243 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 244 sample--;
xorjoep 1:24714b45cd1b 245 }
xorjoep 1:24714b45cd1b 246
xorjoep 1:24714b45cd1b 247 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
xorjoep 1:24714b45cd1b 248 ** No loop unrolling is used. */
xorjoep 1:24714b45cd1b 249 sample = (blockSize & 0x3U);
xorjoep 1:24714b45cd1b 250
xorjoep 1:24714b45cd1b 251 while (sample > 0U)
xorjoep 1:24714b45cd1b 252 {
xorjoep 1:24714b45cd1b 253 /* Read the input */
xorjoep 1:24714b45cd1b 254 Xn = *pIn++;
xorjoep 1:24714b45cd1b 255
xorjoep 1:24714b45cd1b 256 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 257
xorjoep 1:24714b45cd1b 258 /* acc = b0 * x[n] */
xorjoep 1:24714b45cd1b 259 acc = (q63_t) b0 *Xn;
xorjoep 1:24714b45cd1b 260 /* acc += b1 * x[n-1] */
xorjoep 1:24714b45cd1b 261 acc += (q63_t) b1 *Xn1;
xorjoep 1:24714b45cd1b 262 /* acc += b[2] * x[n-2] */
xorjoep 1:24714b45cd1b 263 acc += (q63_t) b2 *Xn2;
xorjoep 1:24714b45cd1b 264 /* acc += a1 * y[n-1] */
xorjoep 1:24714b45cd1b 265 acc += (q63_t) a1 *Yn1;
xorjoep 1:24714b45cd1b 266 /* acc += a2 * y[n-2] */
xorjoep 1:24714b45cd1b 267 acc += (q63_t) a2 *Yn2;
xorjoep 1:24714b45cd1b 268
xorjoep 1:24714b45cd1b 269 /* The result is converted to 1.31 */
xorjoep 1:24714b45cd1b 270 acc = acc >> lShift;
xorjoep 1:24714b45cd1b 271
xorjoep 1:24714b45cd1b 272 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 273 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 274 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 275 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 276 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 277 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 278 Xn2 = Xn1;
xorjoep 1:24714b45cd1b 279 Xn1 = Xn;
xorjoep 1:24714b45cd1b 280 Yn2 = Yn1;
xorjoep 1:24714b45cd1b 281 Yn1 = (q31_t) acc;
xorjoep 1:24714b45cd1b 282
xorjoep 1:24714b45cd1b 283 /* Store the output in the destination buffer. */
xorjoep 1:24714b45cd1b 284 *pOut++ = (q31_t) acc;
xorjoep 1:24714b45cd1b 285
xorjoep 1:24714b45cd1b 286 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 287 sample--;
xorjoep 1:24714b45cd1b 288 }
xorjoep 1:24714b45cd1b 289
xorjoep 1:24714b45cd1b 290 /* The first stage goes from the input buffer to the output buffer. */
xorjoep 1:24714b45cd1b 291 /* Subsequent stages occur in-place in the output buffer */
xorjoep 1:24714b45cd1b 292 pIn = pDst;
xorjoep 1:24714b45cd1b 293
xorjoep 1:24714b45cd1b 294 /* Reset to destination pointer */
xorjoep 1:24714b45cd1b 295 pOut = pDst;
xorjoep 1:24714b45cd1b 296
xorjoep 1:24714b45cd1b 297 /* Store the updated state variables back into the pState array */
xorjoep 1:24714b45cd1b 298 *pState++ = Xn1;
xorjoep 1:24714b45cd1b 299 *pState++ = Xn2;
xorjoep 1:24714b45cd1b 300 *pState++ = Yn1;
xorjoep 1:24714b45cd1b 301 *pState++ = Yn2;
xorjoep 1:24714b45cd1b 302
xorjoep 1:24714b45cd1b 303 } while (--stage);
xorjoep 1:24714b45cd1b 304
xorjoep 1:24714b45cd1b 305 #else
xorjoep 1:24714b45cd1b 306
xorjoep 1:24714b45cd1b 307 /* Run the below code for Cortex-M0 */
xorjoep 1:24714b45cd1b 308
xorjoep 1:24714b45cd1b 309 do
xorjoep 1:24714b45cd1b 310 {
xorjoep 1:24714b45cd1b 311 /* Reading the coefficients */
xorjoep 1:24714b45cd1b 312 b0 = *pCoeffs++;
xorjoep 1:24714b45cd1b 313 b1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 314 b2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 315 a1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 316 a2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 317
xorjoep 1:24714b45cd1b 318 /* Reading the state values */
xorjoep 1:24714b45cd1b 319 Xn1 = pState[0];
xorjoep 1:24714b45cd1b 320 Xn2 = pState[1];
xorjoep 1:24714b45cd1b 321 Yn1 = pState[2];
xorjoep 1:24714b45cd1b 322 Yn2 = pState[3];
xorjoep 1:24714b45cd1b 323
xorjoep 1:24714b45cd1b 324 /* The variables acc holds the output value that is computed:
xorjoep 1:24714b45cd1b 325 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 326 */
xorjoep 1:24714b45cd1b 327
xorjoep 1:24714b45cd1b 328 sample = blockSize;
xorjoep 1:24714b45cd1b 329
xorjoep 1:24714b45cd1b 330 while (sample > 0U)
xorjoep 1:24714b45cd1b 331 {
xorjoep 1:24714b45cd1b 332 /* Read the input */
xorjoep 1:24714b45cd1b 333 Xn = *pIn++;
xorjoep 1:24714b45cd1b 334
xorjoep 1:24714b45cd1b 335 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 336 /* acc = b0 * x[n] */
xorjoep 1:24714b45cd1b 337 acc = (q63_t) b0 *Xn;
xorjoep 1:24714b45cd1b 338
xorjoep 1:24714b45cd1b 339 /* acc += b1 * x[n-1] */
xorjoep 1:24714b45cd1b 340 acc += (q63_t) b1 *Xn1;
xorjoep 1:24714b45cd1b 341 /* acc += b[2] * x[n-2] */
xorjoep 1:24714b45cd1b 342 acc += (q63_t) b2 *Xn2;
xorjoep 1:24714b45cd1b 343 /* acc += a1 * y[n-1] */
xorjoep 1:24714b45cd1b 344 acc += (q63_t) a1 *Yn1;
xorjoep 1:24714b45cd1b 345 /* acc += a2 * y[n-2] */
xorjoep 1:24714b45cd1b 346 acc += (q63_t) a2 *Yn2;
xorjoep 1:24714b45cd1b 347
xorjoep 1:24714b45cd1b 348 /* The result is converted to 1.31 */
xorjoep 1:24714b45cd1b 349 acc = acc >> lShift;
xorjoep 1:24714b45cd1b 350
xorjoep 1:24714b45cd1b 351 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 352 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 353 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 354 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 355 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 356 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 357 Xn2 = Xn1;
xorjoep 1:24714b45cd1b 358 Xn1 = Xn;
xorjoep 1:24714b45cd1b 359 Yn2 = Yn1;
xorjoep 1:24714b45cd1b 360 Yn1 = (q31_t) acc;
xorjoep 1:24714b45cd1b 361
xorjoep 1:24714b45cd1b 362 /* Store the output in the destination buffer. */
xorjoep 1:24714b45cd1b 363 *pOut++ = (q31_t) acc;
xorjoep 1:24714b45cd1b 364
xorjoep 1:24714b45cd1b 365 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 366 sample--;
xorjoep 1:24714b45cd1b 367 }
xorjoep 1:24714b45cd1b 368
xorjoep 1:24714b45cd1b 369 /* The first stage goes from the input buffer to the output buffer. */
xorjoep 1:24714b45cd1b 370 /* Subsequent stages occur in-place in the output buffer */
xorjoep 1:24714b45cd1b 371 pIn = pDst;
xorjoep 1:24714b45cd1b 372
xorjoep 1:24714b45cd1b 373 /* Reset to destination pointer */
xorjoep 1:24714b45cd1b 374 pOut = pDst;
xorjoep 1:24714b45cd1b 375
xorjoep 1:24714b45cd1b 376 /* Store the updated state variables back into the pState array */
xorjoep 1:24714b45cd1b 377 *pState++ = Xn1;
xorjoep 1:24714b45cd1b 378 *pState++ = Xn2;
xorjoep 1:24714b45cd1b 379 *pState++ = Yn1;
xorjoep 1:24714b45cd1b 380 *pState++ = Yn2;
xorjoep 1:24714b45cd1b 381
xorjoep 1:24714b45cd1b 382 } while (--stage);
xorjoep 1:24714b45cd1b 383
xorjoep 1:24714b45cd1b 384 #endif /* #if defined (ARM_MATH_DSP) */
xorjoep 1:24714b45cd1b 385 }
xorjoep 1:24714b45cd1b 386
xorjoep 1:24714b45cd1b 387
xorjoep 1:24714b45cd1b 388
xorjoep 1:24714b45cd1b 389
xorjoep 1:24714b45cd1b 390 /**
xorjoep 1:24714b45cd1b 391 * @} end of BiquadCascadeDF1 group
xorjoep 1:24714b45cd1b 392 */