arm_biquad_cascade_df2T_init_f32.c

00001 /* ----------------------------------------------------------------------
00002  * Project:      CMSIS DSP Library
00003  * Title:        arm_biquad_cascade_df2T_init_f32.c
00004  * Description:  Initialization function for floating-point transposed direct form II Biquad cascade filter
00005  *
00006  * $Date:        27. January 2017
00007  * $Revision:    V.1.5.1
00008  *
00009  * Target Processor: Cortex-M cores
00010  * -------------------------------------------------------------------- */
00011 /*
00012  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
00013  *
00014  * SPDX-License-Identifier: Apache-2.0
00015  *
00016  * Licensed under the Apache License, Version 2.0 (the License); you may
00017  * not use this file except in compliance with the License.
00018  * You may obtain a copy of the License at
00019  *
00020  * www.apache.org/licenses/LICENSE-2.0
00021  *
00022  * Unless required by applicable law or agreed to in writing, software
00023  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00024  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00025  * See the License for the specific language governing permissions and
00026  * limitations under the License.
00027  */
00028 
00029 #include "arm_math.h"
00030 
00031 /**
00032  * @ingroup groupFilters
00033  */
00034 
00035 /**
00036  * @addtogroup BiquadCascadeDF2T
00037  * @{
00038  */
00039 
00040 /**
00041  * @brief  Initialization function for the floating-point transposed direct form II Biquad cascade filter.
00042  * @param[in,out] *S           points to an instance of the filter data structure.
00043  * @param[in]     numStages    number of 2nd order stages in the filter.
00044  * @param[in]     *pCoeffs     points to the filter coefficients.
00045  * @param[in]     *pState      points to the state buffer.
00046  * @return        none
00047  *
00048  * <b>Coefficient and State Ordering:</b>
00049  * \par
00050  * The coefficients are stored in the array <code>pCoeffs</code> in the following order:
00051  * <pre>
00052  *     {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}
00053  * </pre>
00054  *
00055  * \par
00056  * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,
00057  * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,
00058  * and so on.  The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.
00059  *
00060  * \par
00061  * The <code>pState</code> is a pointer to state array.
00062  * Each Biquad stage has 2 state variables <code>d1,</code> and <code>d2</code>.
00063  * The 2 state variables for stage 1 are first, then the 2 state variables for stage 2, and so on.
00064  * The state array has a total length of <code>2*numStages</code> values.
00065  * The state variables are updated after each block of data is processed; the coefficients are untouched.
00066  */
00067 
00068 void arm_biquad_cascade_df2T_init_f32(
00069   arm_biquad_cascade_df2T_instance_f32 * S,
00070   uint8_t numStages,
00071   float32_t * pCoeffs,
00072   float32_t * pState)
00073 {
00074   /* Assign filter stages */
00075   S->numStages = numStages;
00076 
00077   /* Assign coefficient pointer */
00078   S->pCoeffs = pCoeffs;
00079 
00080   /* Clear state buffer and size is always 2 * numStages */
00081   memset(pState, 0, (2U * (uint32_t) numStages) * sizeof(float32_t));
00082 
00083   /* Assign state pointer */
00084   S->pState = pState;
00085 }
00086 
00087 /**
00088  * @} end of BiquadCascadeDF2T group
00089  */
00090