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The CMSIS DSP 5 library

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functions/FilteringFunctions/arm_biquad_cascade_df1_init_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 
headers is a folder not a library

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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_init_f32.c
xorjoep 1:24714b45cd1b 4 * Description: Floating-point Biquad cascade DirectFormI(DF1) filter initialization function
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 * @details
xorjoep 1:24714b45cd1b 42 * @brief Initialization function for the floating-point Biquad cascade filter.
xorjoep 1:24714b45cd1b 43 * @param[in,out] *S points to an instance of the floating-point Biquad cascade structure.
xorjoep 1:24714b45cd1b 44 * @param[in] numStages number of 2nd order stages in the filter.
xorjoep 1:24714b45cd1b 45 * @param[in] *pCoeffs points to the filter coefficients array.
xorjoep 1:24714b45cd1b 46 * @param[in] *pState points to the state array.
xorjoep 1:24714b45cd1b 47 * @return none
xorjoep 1:24714b45cd1b 48 *
xorjoep 1:24714b45cd1b 49 *
xorjoep 1:24714b45cd1b 50 * <b>Coefficient and State Ordering:</b>
xorjoep 1:24714b45cd1b 51 *
xorjoep 1:24714b45cd1b 52 * \par
xorjoep 1:24714b45cd1b 53 * The coefficients are stored in the array <code>pCoeffs</code> in the following order:
xorjoep 1:24714b45cd1b 54 * <pre>
xorjoep 1:24714b45cd1b 55 * {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
xorjoep 1:24714b45cd1b 56 * </pre>
xorjoep 1:24714b45cd1b 57 *
xorjoep 1:24714b45cd1b 58 * \par
xorjoep 1:24714b45cd1b 59 * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,
xorjoep 1:24714b45cd1b 60 * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,
xorjoep 1:24714b45cd1b 61 * and so on. The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.
xorjoep 1:24714b45cd1b 62 *
xorjoep 1:24714b45cd1b 63 * \par
xorjoep 1:24714b45cd1b 64 * The <code>pState</code> is a pointer to state array.
xorjoep 1:24714b45cd1b 65 * 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 66 * The state variables are arranged in the <code>pState</code> array as:
xorjoep 1:24714b45cd1b 67 * <pre>
xorjoep 1:24714b45cd1b 68 * {x[n-1], x[n-2], y[n-1], y[n-2]}
xorjoep 1:24714b45cd1b 69 * </pre>
xorjoep 1:24714b45cd1b 70 * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.
xorjoep 1:24714b45cd1b 71 * The state array has a total length of <code>4*numStages</code> values.
xorjoep 1:24714b45cd1b 72 * The state variables are updated after each block of data is processed; the coefficients are untouched.
xorjoep 1:24714b45cd1b 73 *
xorjoep 1:24714b45cd1b 74 */
xorjoep 1:24714b45cd1b 75
xorjoep 1:24714b45cd1b 76 void arm_biquad_cascade_df1_init_f32(
xorjoep 1:24714b45cd1b 77 arm_biquad_casd_df1_inst_f32 * S,
xorjoep 1:24714b45cd1b 78 uint8_t numStages,
xorjoep 1:24714b45cd1b 79 float32_t * pCoeffs,
xorjoep 1:24714b45cd1b 80 float32_t * pState)
xorjoep 1:24714b45cd1b 81 {
xorjoep 1:24714b45cd1b 82 /* Assign filter stages */
xorjoep 1:24714b45cd1b 83 S->numStages = numStages;
xorjoep 1:24714b45cd1b 84
xorjoep 1:24714b45cd1b 85 /* Assign coefficient pointer */
xorjoep 1:24714b45cd1b 86 S->pCoeffs = pCoeffs;
xorjoep 1:24714b45cd1b 87
xorjoep 1:24714b45cd1b 88 /* Clear state buffer and size is always 4 * numStages */
xorjoep 1:24714b45cd1b 89 memset(pState, 0, (4U * (uint32_t) numStages) * sizeof(float32_t));
xorjoep 1:24714b45cd1b 90
xorjoep 1:24714b45cd1b 91 /* Assign state pointer */
xorjoep 1:24714b45cd1b 92 S->pState = pState;
xorjoep 1:24714b45cd1b 93 }
xorjoep 1:24714b45cd1b 94
xorjoep 1:24714b45cd1b 95 /**
xorjoep 1:24714b45cd1b 96 * @} end of BiquadCascadeDF1 group
xorjoep 1:24714b45cd1b 97 */