arm_biquad_cascade_df1_init_f32.c

00001 /*-----------------------------------------------------------------------------    
00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        17. January 2013
00005 * $Revision:    V1.4.1
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_biquad_cascade_df1_init_f32.c    
00009 *    
00010 * Description:  floating-point Biquad cascade DirectFormI(DF1) filter initialization function.    
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.    
00039 * ---------------------------------------------------------------------------*/
00040 
00041 #include "arm_math.h"
00042 
00043 /**    
00044  * @ingroup groupFilters    
00045  */
00046 
00047 /**    
00048  * @addtogroup BiquadCascadeDF1    
00049  * @{    
00050  */
00051 
00052 /**    
00053  * @details    
00054  * @brief  Initialization function for the floating-point Biquad cascade filter.    
00055  * @param[in,out] *S           points to an instance of the floating-point Biquad cascade structure.    
00056  * @param[in]     numStages    number of 2nd order stages in the filter.    
00057  * @param[in]     *pCoeffs     points to the filter coefficients array.    
00058  * @param[in]     *pState      points to the state array.    
00059  * @return        none    
00060  *    
00061  *    
00062  * <b>Coefficient and State Ordering:</b>    
00063  *    
00064  * \par    
00065  * The coefficients are stored in the array <code>pCoeffs</code> in the following order:    
00066  * <pre>    
00067  *     {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}    
00068  * </pre>    
00069  *    
00070  * \par    
00071  * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,    
00072  * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,    
00073  * and so on.  The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.    
00074  *    
00075  * \par    
00076  * The <code>pState</code> is a pointer to state array.    
00077  * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.    
00078  * The state variables are arranged in the <code>pState</code> array as:    
00079  * <pre>    
00080  *     {x[n-1], x[n-2], y[n-1], y[n-2]}    
00081  * </pre>    
00082  * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.    
00083  * The state array has a total length of <code>4*numStages</code> values.    
00084  * The state variables are updated after each block of data is processed; the coefficients are untouched.    
00085  *    
00086  */
00087 
00088 void arm_biquad_cascade_df1_init_f32(
00089   arm_biquad_casd_df1_inst_f32 * S,
00090   uint8_t numStages,
00091   float32_t * pCoeffs,
00092   float32_t * pState)
00093 {
00094   /* Assign filter stages */
00095   S->numStages = numStages;
00096 
00097   /* Assign coefficient pointer */
00098   S->pCoeffs = pCoeffs;
00099 
00100   /* Clear state buffer and size is always 4 * numStages */
00101   memset(pState, 0, (4u * (uint32_t) numStages) * sizeof(float32_t));
00102 
00103   /* Assign state pointer */
00104   S->pState = pState;
00105 }
00106 
00107 /**    
00108  * @} end of BiquadCascadeDF1 group    
00109  */