arm_biquad_cascade_df2T_init_f32.c

00001 /*-----------------------------------------------------------------------------  
00002 * Copyright (C) 2010 ARM Limited. All rights reserved.  
00003 *  
00004 * $Date:        29. November 2010  
00005 * $Revision:    V1.0.3  
00006 *  
00007 * Project:      CMSIS DSP Library  
00008 * Title:        arm_biquad_cascade_df2T_init_f32.c  
00009 *  
00010 * Description:  Initialization function for the floating-point transposed 
00011 *               direct form II Biquad cascade filter. 
00012 *  
00013 * Target Processor: Cortex-M4/Cortex-M3
00014 *  
00015 * Version 1.0.3 2010/11/29 
00016 *    Re-organized the CMSIS folders and updated documentation.  
00017 *   
00018 * Version 1.0.2 2010/11/11  
00019 *    Documentation updated.   
00020 *  
00021 * Version 1.0.1 2010/10/05   
00022 *    Production release and review comments incorporated.  
00023 *  
00024 * Version 1.0.0 2010/09/20   
00025 *    Production release and review comments incorporated  
00026 *  
00027 * Version 0.0.7  2010/06/10   
00028 *    Misra-C changes done  
00029 * ---------------------------------------------------------------------------*/ 
00030  
00031 #include "arm_math.h" 
00032  
00033 /**  
00034  * @ingroup groupFilters  
00035  */ 
00036  
00037 /**  
00038  * @addtogroup BiquadCascadeDF2T  
00039  * @{  
00040  */ 
00041  
00042 /** 
00043  * @brief  Initialization function for the floating-point transposed direct form II Biquad cascade filter. 
00044  * @param[in,out] *S           points to an instance of the filter data structure. 
00045  * @param[in]     numStages    number of 2nd order stages in the filter. 
00046  * @param[in]     *pCoeffs     points to the filter coefficients. 
00047  * @param[in]     *pState      points to the state buffer. 
00048  * @return        none 
00049  *  
00050  * <b>Coefficient and State Ordering:</b>  
00051  * \par  
00052  * The coefficients are stored in the array <code>pCoeffs</code> in the following order:  
00053  * <pre>  
00054  *     {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}  
00055  * </pre>  
00056  *  
00057  * \par  
00058  * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,  
00059  * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,  
00060  * and so on.  The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.  
00061  *  
00062  * \par  
00063  * The <code>pState</code> is a pointer to state array.  
00064  * Each Biquad stage has 2 state variables <code>d1,</code> and <code>d2</code>.  
00065  * The 2 state variables for stage 1 are first, then the 2 state variables for stage 2, and so on.  
00066  * The state array has a total length of <code>2*numStages</code> values.  
00067  * The state variables are updated after each block of data is processed; the coefficients are untouched.  
00068  */ 
00069  
00070 void arm_biquad_cascade_df2T_init_f32( 
00071   arm_biquad_cascade_df2T_instance_f32 * S, 
00072   uint8_t numStages, 
00073   float32_t * pCoeffs, 
00074   float32_t * pState) 
00075 { 
00076   /* Assign filter stages */ 
00077   S->numStages = numStages; 
00078  
00079   /* Assign coefficient pointer */ 
00080   S->pCoeffs = pCoeffs; 
00081  
00082   /* Clear state buffer and size is always 2 * numStages */ 
00083   memset(pState, 0, (2u * (uint32_t) numStages) * sizeof(float32_t)); 
00084  
00085   /* Assign state pointer */ 
00086   S->pState = pState; 
00087 } 
00088  
00089 /**  
00090  * @} end of BiquadCascadeDF2T group  
00091  */