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functions/FilteringFunctions/arm_biquad_cascade_df1_f32.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_f32.c
xorjoep 1:24714b45cd1b 4 * Description: Processing function for the floating-point Biquad cascade DirectFormI(DF1) 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 * @defgroup BiquadCascadeDF1 Biquad Cascade IIR Filters Using Direct Form I Structure
xorjoep 1:24714b45cd1b 37 *
xorjoep 1:24714b45cd1b 38 * This set of functions implements arbitrary order recursive (IIR) filters.
xorjoep 1:24714b45cd1b 39 * The filters are implemented as a cascade of second order Biquad sections.
xorjoep 1:24714b45cd1b 40 * The functions support Q15, Q31 and floating-point data types.
xorjoep 1:24714b45cd1b 41 * Fast version of Q15 and Q31 also supported on CortexM4 and Cortex-M3.
xorjoep 1:24714b45cd1b 42 *
xorjoep 1:24714b45cd1b 43 * The functions operate on blocks of input and output data and each call to the function
xorjoep 1:24714b45cd1b 44 * processes <code>blockSize</code> samples through the filter.
xorjoep 1:24714b45cd1b 45 * <code>pSrc</code> points to the array of input data and
xorjoep 1:24714b45cd1b 46 * <code>pDst</code> points to the array of output data.
xorjoep 1:24714b45cd1b 47 * Both arrays contain <code>blockSize</code> values.
xorjoep 1:24714b45cd1b 48 *
xorjoep 1:24714b45cd1b 49 * \par Algorithm
xorjoep 1:24714b45cd1b 50 * Each Biquad stage implements a second order filter using the difference equation:
xorjoep 1:24714b45cd1b 51 * <pre>
xorjoep 1:24714b45cd1b 52 * y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 53 * </pre>
xorjoep 1:24714b45cd1b 54 * A Direct Form I algorithm is used with 5 coefficients and 4 state variables per stage.
xorjoep 1:24714b45cd1b 55 * \image html Biquad.gif "Single Biquad filter stage"
xorjoep 1:24714b45cd1b 56 * Coefficients <code>b0, b1 and b2 </code> multiply the input signal <code>x[n]</code> and are referred to as the feedforward coefficients.
xorjoep 1:24714b45cd1b 57 * Coefficients <code>a1</code> and <code>a2</code> multiply the output signal <code>y[n]</code> and are referred to as the feedback coefficients.
xorjoep 1:24714b45cd1b 58 * Pay careful attention to the sign of the feedback coefficients.
xorjoep 1:24714b45cd1b 59 * Some design tools use the difference equation
xorjoep 1:24714b45cd1b 60 * <pre>
xorjoep 1:24714b45cd1b 61 * y[n] = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] - a1 * y[n-1] - a2 * y[n-2]
xorjoep 1:24714b45cd1b 62 * </pre>
xorjoep 1:24714b45cd1b 63 * In this case the feedback coefficients <code>a1</code> and <code>a2</code> must be negated when used with the CMSIS DSP Library.
xorjoep 1:24714b45cd1b 64 *
xorjoep 1:24714b45cd1b 65 * \par
xorjoep 1:24714b45cd1b 66 * Higher order filters are realized as a cascade of second order sections.
xorjoep 1:24714b45cd1b 67 * <code>numStages</code> refers to the number of second order stages used.
xorjoep 1:24714b45cd1b 68 * For example, an 8th order filter would be realized with <code>numStages=4</code> second order stages.
xorjoep 1:24714b45cd1b 69 * \image html BiquadCascade.gif "8th order filter using a cascade of Biquad stages"
xorjoep 1:24714b45cd1b 70 * A 9th order filter would be realized with <code>numStages=5</code> second order stages with the coefficients for one of the stages configured as a first order filter (<code>b2=0</code> and <code>a2=0</code>).
xorjoep 1:24714b45cd1b 71 *
xorjoep 1:24714b45cd1b 72 * \par
xorjoep 1:24714b45cd1b 73 * The <code>pState</code> points to state variables array.
xorjoep 1:24714b45cd1b 74 * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.
xorjoep 1:24714b45cd1b 75 * The state variables are arranged in the <code>pState</code> array as:
xorjoep 1:24714b45cd1b 76 * <pre>
xorjoep 1:24714b45cd1b 77 * {x[n-1], x[n-2], y[n-1], y[n-2]}
xorjoep 1:24714b45cd1b 78 * </pre>
xorjoep 1:24714b45cd1b 79 *
xorjoep 1:24714b45cd1b 80 * \par
xorjoep 1:24714b45cd1b 81 * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.
xorjoep 1:24714b45cd1b 82 * The state array has a total length of <code>4*numStages</code> values.
xorjoep 1:24714b45cd1b 83 * The state variables are updated after each block of data is processed, the coefficients are untouched.
xorjoep 1:24714b45cd1b 84 *
xorjoep 1:24714b45cd1b 85 * \par Instance Structure
xorjoep 1:24714b45cd1b 86 * The coefficients and state variables for a filter are stored together in an instance data structure.
xorjoep 1:24714b45cd1b 87 * A separate instance structure must be defined for each filter.
xorjoep 1:24714b45cd1b 88 * Coefficient arrays may be shared among several instances while state variable arrays cannot be shared.
xorjoep 1:24714b45cd1b 89 * There are separate instance structure declarations for each of the 3 supported data types.
xorjoep 1:24714b45cd1b 90 *
xorjoep 1:24714b45cd1b 91 * \par Init Functions
xorjoep 1:24714b45cd1b 92 * There is also an associated initialization function for each data type.
xorjoep 1:24714b45cd1b 93 * The initialization function performs following operations:
xorjoep 1:24714b45cd1b 94 * - Sets the values of the internal structure fields.
xorjoep 1:24714b45cd1b 95 * - Zeros out the values in the state buffer.
xorjoep 1:24714b45cd1b 96 * To do this manually without calling the init function, assign the follow subfields of the instance structure:
xorjoep 1:24714b45cd1b 97 * numStages, pCoeffs, pState. Also set all of the values in pState to zero.
xorjoep 1:24714b45cd1b 98 *
xorjoep 1:24714b45cd1b 99 * \par
xorjoep 1:24714b45cd1b 100 * Use of the initialization function is optional.
xorjoep 1:24714b45cd1b 101 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
xorjoep 1:24714b45cd1b 102 * To place an instance structure into a const data section, the instance structure must be manually initialized.
xorjoep 1:24714b45cd1b 103 * Set the values in the state buffer to zeros before static initialization.
xorjoep 1:24714b45cd1b 104 * The code below statically initializes each of the 3 different data type filter instance structures
xorjoep 1:24714b45cd1b 105 * <pre>
xorjoep 1:24714b45cd1b 106 * arm_biquad_casd_df1_inst_f32 S1 = {numStages, pState, pCoeffs};
xorjoep 1:24714b45cd1b 107 * arm_biquad_casd_df1_inst_q15 S2 = {numStages, pState, pCoeffs, postShift};
xorjoep 1:24714b45cd1b 108 * arm_biquad_casd_df1_inst_q31 S3 = {numStages, pState, pCoeffs, postShift};
xorjoep 1:24714b45cd1b 109 * </pre>
xorjoep 1:24714b45cd1b 110 * where <code>numStages</code> is the number of Biquad stages in the filter; <code>pState</code> is the address of the state buffer;
xorjoep 1:24714b45cd1b 111 * <code>pCoeffs</code> is the address of the coefficient buffer; <code>postShift</code> shift to be applied.
xorjoep 1:24714b45cd1b 112 *
xorjoep 1:24714b45cd1b 113 * \par Fixed-Point Behavior
xorjoep 1:24714b45cd1b 114 * Care must be taken when using the Q15 and Q31 versions of the Biquad Cascade filter functions.
xorjoep 1:24714b45cd1b 115 * Following issues must be considered:
xorjoep 1:24714b45cd1b 116 * - Scaling of coefficients
xorjoep 1:24714b45cd1b 117 * - Filter gain
xorjoep 1:24714b45cd1b 118 * - Overflow and saturation
xorjoep 1:24714b45cd1b 119 *
xorjoep 1:24714b45cd1b 120 * \par
xorjoep 1:24714b45cd1b 121 * <b>Scaling of coefficients: </b>
xorjoep 1:24714b45cd1b 122 * Filter coefficients are represented as fractional values and
xorjoep 1:24714b45cd1b 123 * coefficients are restricted to lie in the range <code>[-1 +1)</code>.
xorjoep 1:24714b45cd1b 124 * The fixed-point functions have an additional scaling parameter <code>postShift</code>
xorjoep 1:24714b45cd1b 125 * which allow the filter coefficients to exceed the range <code>[+1 -1)</code>.
xorjoep 1:24714b45cd1b 126 * At the output of the filter's accumulator is a shift register which shifts the result by <code>postShift</code> bits.
xorjoep 1:24714b45cd1b 127 * \image html BiquadPostshift.gif "Fixed-point Biquad with shift by postShift bits after accumulator"
xorjoep 1:24714b45cd1b 128 * This essentially scales the filter coefficients by <code>2^postShift</code>.
xorjoep 1:24714b45cd1b 129 * For example, to realize the coefficients
xorjoep 1:24714b45cd1b 130 * <pre>
xorjoep 1:24714b45cd1b 131 * {1.5, -0.8, 1.2, 1.6, -0.9}
xorjoep 1:24714b45cd1b 132 * </pre>
xorjoep 1:24714b45cd1b 133 * set the pCoeffs array to:
xorjoep 1:24714b45cd1b 134 * <pre>
xorjoep 1:24714b45cd1b 135 * {0.75, -0.4, 0.6, 0.8, -0.45}
xorjoep 1:24714b45cd1b 136 * </pre>
xorjoep 1:24714b45cd1b 137 * and set <code>postShift=1</code>
xorjoep 1:24714b45cd1b 138 *
xorjoep 1:24714b45cd1b 139 * \par
xorjoep 1:24714b45cd1b 140 * <b>Filter gain: </b>
xorjoep 1:24714b45cd1b 141 * The frequency response of a Biquad filter is a function of its coefficients.
xorjoep 1:24714b45cd1b 142 * It is possible for the gain through the filter to exceed 1.0 meaning that the filter increases the amplitude of certain frequencies.
xorjoep 1:24714b45cd1b 143 * This means that an input signal with amplitude < 1.0 may result in an output > 1.0 and these are saturated or overflowed based on the implementation of the filter.
xorjoep 1:24714b45cd1b 144 * To avoid this behavior the filter needs to be scaled down such that its peak gain < 1.0 or the input signal must be scaled down so that the combination of input and filter are never overflowed.
xorjoep 1:24714b45cd1b 145 *
xorjoep 1:24714b45cd1b 146 * \par
xorjoep 1:24714b45cd1b 147 * <b>Overflow and saturation: </b>
xorjoep 1:24714b45cd1b 148 * For Q15 and Q31 versions, it is described separately as part of the function specific documentation below.
xorjoep 1:24714b45cd1b 149 */
xorjoep 1:24714b45cd1b 150
xorjoep 1:24714b45cd1b 151 /**
xorjoep 1:24714b45cd1b 152 * @addtogroup BiquadCascadeDF1
xorjoep 1:24714b45cd1b 153 * @{
xorjoep 1:24714b45cd1b 154 */
xorjoep 1:24714b45cd1b 155
xorjoep 1:24714b45cd1b 156 /**
xorjoep 1:24714b45cd1b 157 * @param[in] *S points to an instance of the floating-point Biquad cascade structure.
xorjoep 1:24714b45cd1b 158 * @param[in] *pSrc points to the block of input data.
xorjoep 1:24714b45cd1b 159 * @param[out] *pDst points to the block of output data.
xorjoep 1:24714b45cd1b 160 * @param[in] blockSize number of samples to process per call.
xorjoep 1:24714b45cd1b 161 * @return none.
xorjoep 1:24714b45cd1b 162 *
xorjoep 1:24714b45cd1b 163 */
xorjoep 1:24714b45cd1b 164
xorjoep 1:24714b45cd1b 165 void arm_biquad_cascade_df1_f32(
xorjoep 1:24714b45cd1b 166 const arm_biquad_casd_df1_inst_f32 * S,
xorjoep 1:24714b45cd1b 167 float32_t * pSrc,
xorjoep 1:24714b45cd1b 168 float32_t * pDst,
xorjoep 1:24714b45cd1b 169 uint32_t blockSize)
xorjoep 1:24714b45cd1b 170 {
xorjoep 1:24714b45cd1b 171 float32_t *pIn = pSrc; /* source pointer */
xorjoep 1:24714b45cd1b 172 float32_t *pOut = pDst; /* destination pointer */
xorjoep 1:24714b45cd1b 173 float32_t *pState = S->pState; /* pState pointer */
xorjoep 1:24714b45cd1b 174 float32_t *pCoeffs = S->pCoeffs; /* coefficient pointer */
xorjoep 1:24714b45cd1b 175 float32_t acc; /* Simulates the accumulator */
xorjoep 1:24714b45cd1b 176 float32_t b0, b1, b2, a1, a2; /* Filter coefficients */
xorjoep 1:24714b45cd1b 177 float32_t Xn1, Xn2, Yn1, Yn2; /* Filter pState variables */
xorjoep 1:24714b45cd1b 178 float32_t Xn; /* temporary input */
xorjoep 1:24714b45cd1b 179 uint32_t sample, stage = S->numStages; /* loop counters */
xorjoep 1:24714b45cd1b 180
xorjoep 1:24714b45cd1b 181
xorjoep 1:24714b45cd1b 182 #if defined (ARM_MATH_DSP)
xorjoep 1:24714b45cd1b 183
xorjoep 1:24714b45cd1b 184 /* Run the below code for Cortex-M4 and Cortex-M3 */
xorjoep 1:24714b45cd1b 185
xorjoep 1:24714b45cd1b 186 do
xorjoep 1:24714b45cd1b 187 {
xorjoep 1:24714b45cd1b 188 /* Reading the coefficients */
xorjoep 1:24714b45cd1b 189 b0 = *pCoeffs++;
xorjoep 1:24714b45cd1b 190 b1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 191 b2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 192 a1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 193 a2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 194
xorjoep 1:24714b45cd1b 195 /* Reading the pState values */
xorjoep 1:24714b45cd1b 196 Xn1 = pState[0];
xorjoep 1:24714b45cd1b 197 Xn2 = pState[1];
xorjoep 1:24714b45cd1b 198 Yn1 = pState[2];
xorjoep 1:24714b45cd1b 199 Yn2 = pState[3];
xorjoep 1:24714b45cd1b 200
xorjoep 1:24714b45cd1b 201 /* Apply loop unrolling and compute 4 output values simultaneously. */
xorjoep 1:24714b45cd1b 202 /* The variable acc hold output values that are being computed:
xorjoep 1:24714b45cd1b 203 *
xorjoep 1:24714b45cd1b 204 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 205 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 206 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 207 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 208 */
xorjoep 1:24714b45cd1b 209
xorjoep 1:24714b45cd1b 210 sample = blockSize >> 2U;
xorjoep 1:24714b45cd1b 211
xorjoep 1:24714b45cd1b 212 /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
xorjoep 1:24714b45cd1b 213 ** a second loop below computes the remaining 1 to 3 samples. */
xorjoep 1:24714b45cd1b 214 while (sample > 0U)
xorjoep 1:24714b45cd1b 215 {
xorjoep 1:24714b45cd1b 216 /* Read the first input */
xorjoep 1:24714b45cd1b 217 Xn = *pIn++;
xorjoep 1:24714b45cd1b 218
xorjoep 1:24714b45cd1b 219 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 220 Yn2 = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn1) + (a2 * Yn2);
xorjoep 1:24714b45cd1b 221
xorjoep 1:24714b45cd1b 222 /* Store the result in the accumulator in the destination buffer. */
xorjoep 1:24714b45cd1b 223 *pOut++ = Yn2;
xorjoep 1:24714b45cd1b 224
xorjoep 1:24714b45cd1b 225 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 226 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 227 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 228 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 229 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 230 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 231
xorjoep 1:24714b45cd1b 232 /* Read the second input */
xorjoep 1:24714b45cd1b 233 Xn2 = *pIn++;
xorjoep 1:24714b45cd1b 234
xorjoep 1:24714b45cd1b 235 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 236 Yn1 = (b0 * Xn2) + (b1 * Xn) + (b2 * Xn1) + (a1 * Yn2) + (a2 * Yn1);
xorjoep 1:24714b45cd1b 237
xorjoep 1:24714b45cd1b 238 /* Store the result in the accumulator in the destination buffer. */
xorjoep 1:24714b45cd1b 239 *pOut++ = Yn1;
xorjoep 1:24714b45cd1b 240
xorjoep 1:24714b45cd1b 241 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 242 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 243 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 244 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 245 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 246 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 247
xorjoep 1:24714b45cd1b 248 /* Read the third input */
xorjoep 1:24714b45cd1b 249 Xn1 = *pIn++;
xorjoep 1:24714b45cd1b 250
xorjoep 1:24714b45cd1b 251 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 252 Yn2 = (b0 * Xn1) + (b1 * Xn2) + (b2 * Xn) + (a1 * Yn1) + (a2 * Yn2);
xorjoep 1:24714b45cd1b 253
xorjoep 1:24714b45cd1b 254 /* Store the result in the accumulator in the destination buffer. */
xorjoep 1:24714b45cd1b 255 *pOut++ = Yn2;
xorjoep 1:24714b45cd1b 256
xorjoep 1:24714b45cd1b 257 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 258 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 259 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 260 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 261 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 262 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 263
xorjoep 1:24714b45cd1b 264 /* Read the forth input */
xorjoep 1:24714b45cd1b 265 Xn = *pIn++;
xorjoep 1:24714b45cd1b 266
xorjoep 1:24714b45cd1b 267 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 268 Yn1 = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn2) + (a2 * Yn1);
xorjoep 1:24714b45cd1b 269
xorjoep 1:24714b45cd1b 270 /* Store the result in the accumulator in the destination buffer. */
xorjoep 1:24714b45cd1b 271 *pOut++ = Yn1;
xorjoep 1:24714b45cd1b 272
xorjoep 1:24714b45cd1b 273 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 274 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 275 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 276 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 277 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 278 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 279 Xn2 = Xn1;
xorjoep 1:24714b45cd1b 280 Xn1 = Xn;
xorjoep 1:24714b45cd1b 281
xorjoep 1:24714b45cd1b 282 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 283 sample--;
xorjoep 1:24714b45cd1b 284
xorjoep 1:24714b45cd1b 285 }
xorjoep 1:24714b45cd1b 286
xorjoep 1:24714b45cd1b 287 /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
xorjoep 1:24714b45cd1b 288 ** No loop unrolling is used. */
xorjoep 1:24714b45cd1b 289 sample = blockSize & 0x3U;
xorjoep 1:24714b45cd1b 290
xorjoep 1:24714b45cd1b 291 while (sample > 0U)
xorjoep 1:24714b45cd1b 292 {
xorjoep 1:24714b45cd1b 293 /* Read the input */
xorjoep 1:24714b45cd1b 294 Xn = *pIn++;
xorjoep 1:24714b45cd1b 295
xorjoep 1:24714b45cd1b 296 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 297 acc = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn1) + (a2 * Yn2);
xorjoep 1:24714b45cd1b 298
xorjoep 1:24714b45cd1b 299 /* Store the result in the accumulator in the destination buffer. */
xorjoep 1:24714b45cd1b 300 *pOut++ = acc;
xorjoep 1:24714b45cd1b 301
xorjoep 1:24714b45cd1b 302 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 303 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 304 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 305 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 306 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 307 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 308 Xn2 = Xn1;
xorjoep 1:24714b45cd1b 309 Xn1 = Xn;
xorjoep 1:24714b45cd1b 310 Yn2 = Yn1;
xorjoep 1:24714b45cd1b 311 Yn1 = acc;
xorjoep 1:24714b45cd1b 312
xorjoep 1:24714b45cd1b 313 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 314 sample--;
xorjoep 1:24714b45cd1b 315
xorjoep 1:24714b45cd1b 316 }
xorjoep 1:24714b45cd1b 317
xorjoep 1:24714b45cd1b 318 /* Store the updated state variables back into the pState array */
xorjoep 1:24714b45cd1b 319 *pState++ = Xn1;
xorjoep 1:24714b45cd1b 320 *pState++ = Xn2;
xorjoep 1:24714b45cd1b 321 *pState++ = Yn1;
xorjoep 1:24714b45cd1b 322 *pState++ = Yn2;
xorjoep 1:24714b45cd1b 323
xorjoep 1:24714b45cd1b 324 /* The first stage goes from the input buffer to the output buffer. */
xorjoep 1:24714b45cd1b 325 /* Subsequent numStages occur in-place in the output buffer */
xorjoep 1:24714b45cd1b 326 pIn = pDst;
xorjoep 1:24714b45cd1b 327
xorjoep 1:24714b45cd1b 328 /* Reset the output pointer */
xorjoep 1:24714b45cd1b 329 pOut = pDst;
xorjoep 1:24714b45cd1b 330
xorjoep 1:24714b45cd1b 331 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 332 stage--;
xorjoep 1:24714b45cd1b 333
xorjoep 1:24714b45cd1b 334 } while (stage > 0U);
xorjoep 1:24714b45cd1b 335
xorjoep 1:24714b45cd1b 336 #else
xorjoep 1:24714b45cd1b 337
xorjoep 1:24714b45cd1b 338 /* Run the below code for Cortex-M0 */
xorjoep 1:24714b45cd1b 339
xorjoep 1:24714b45cd1b 340 do
xorjoep 1:24714b45cd1b 341 {
xorjoep 1:24714b45cd1b 342 /* Reading the coefficients */
xorjoep 1:24714b45cd1b 343 b0 = *pCoeffs++;
xorjoep 1:24714b45cd1b 344 b1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 345 b2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 346 a1 = *pCoeffs++;
xorjoep 1:24714b45cd1b 347 a2 = *pCoeffs++;
xorjoep 1:24714b45cd1b 348
xorjoep 1:24714b45cd1b 349 /* Reading the pState values */
xorjoep 1:24714b45cd1b 350 Xn1 = pState[0];
xorjoep 1:24714b45cd1b 351 Xn2 = pState[1];
xorjoep 1:24714b45cd1b 352 Yn1 = pState[2];
xorjoep 1:24714b45cd1b 353 Yn2 = pState[3];
xorjoep 1:24714b45cd1b 354
xorjoep 1:24714b45cd1b 355 /* The variables acc holds the output value that is computed:
xorjoep 1:24714b45cd1b 356 * acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
xorjoep 1:24714b45cd1b 357 */
xorjoep 1:24714b45cd1b 358
xorjoep 1:24714b45cd1b 359 sample = blockSize;
xorjoep 1:24714b45cd1b 360
xorjoep 1:24714b45cd1b 361 while (sample > 0U)
xorjoep 1:24714b45cd1b 362 {
xorjoep 1:24714b45cd1b 363 /* Read the input */
xorjoep 1:24714b45cd1b 364 Xn = *pIn++;
xorjoep 1:24714b45cd1b 365
xorjoep 1:24714b45cd1b 366 /* acc = b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
xorjoep 1:24714b45cd1b 367 acc = (b0 * Xn) + (b1 * Xn1) + (b2 * Xn2) + (a1 * Yn1) + (a2 * Yn2);
xorjoep 1:24714b45cd1b 368
xorjoep 1:24714b45cd1b 369 /* Store the result in the accumulator in the destination buffer. */
xorjoep 1:24714b45cd1b 370 *pOut++ = acc;
xorjoep 1:24714b45cd1b 371
xorjoep 1:24714b45cd1b 372 /* Every time after the output is computed state should be updated. */
xorjoep 1:24714b45cd1b 373 /* The states should be updated as: */
xorjoep 1:24714b45cd1b 374 /* Xn2 = Xn1 */
xorjoep 1:24714b45cd1b 375 /* Xn1 = Xn */
xorjoep 1:24714b45cd1b 376 /* Yn2 = Yn1 */
xorjoep 1:24714b45cd1b 377 /* Yn1 = acc */
xorjoep 1:24714b45cd1b 378 Xn2 = Xn1;
xorjoep 1:24714b45cd1b 379 Xn1 = Xn;
xorjoep 1:24714b45cd1b 380 Yn2 = Yn1;
xorjoep 1:24714b45cd1b 381 Yn1 = acc;
xorjoep 1:24714b45cd1b 382
xorjoep 1:24714b45cd1b 383 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 384 sample--;
xorjoep 1:24714b45cd1b 385 }
xorjoep 1:24714b45cd1b 386
xorjoep 1:24714b45cd1b 387 /* Store the updated state variables back into the pState array */
xorjoep 1:24714b45cd1b 388 *pState++ = Xn1;
xorjoep 1:24714b45cd1b 389 *pState++ = Xn2;
xorjoep 1:24714b45cd1b 390 *pState++ = Yn1;
xorjoep 1:24714b45cd1b 391 *pState++ = Yn2;
xorjoep 1:24714b45cd1b 392
xorjoep 1:24714b45cd1b 393 /* The first stage goes from the input buffer to the output buffer. */
xorjoep 1:24714b45cd1b 394 /* Subsequent numStages occur in-place in the output buffer */
xorjoep 1:24714b45cd1b 395 pIn = pDst;
xorjoep 1:24714b45cd1b 396
xorjoep 1:24714b45cd1b 397 /* Reset the output pointer */
xorjoep 1:24714b45cd1b 398 pOut = pDst;
xorjoep 1:24714b45cd1b 399
xorjoep 1:24714b45cd1b 400 /* decrement the loop counter */
xorjoep 1:24714b45cd1b 401 stage--;
xorjoep 1:24714b45cd1b 402
xorjoep 1:24714b45cd1b 403 } while (stage > 0U);
xorjoep 1:24714b45cd1b 404
xorjoep 1:24714b45cd1b 405 #endif /* #if defined (ARM_MATH_DSP) */
xorjoep 1:24714b45cd1b 406
xorjoep 1:24714b45cd1b 407 }
xorjoep 1:24714b45cd1b 408
xorjoep 1:24714b45cd1b 409
xorjoep 1:24714b45cd1b 410 /**
xorjoep 1:24714b45cd1b 411 * @} end of BiquadCascadeDF1 group
xorjoep 1:24714b45cd1b 412 */