arm_biquad_cascade_df1_32x64_init_q31.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_df1_32x64_init_q31.c  
00009 *  
00010 * Description:  High precision Q31 Biquad cascade filter initialization function.  
00011 *  
00012 * Target Processor: Cortex-M4/Cortex-M3
00013 *  
00014 * Version 1.0.3 2010/11/29 
00015 *    Re-organized the CMSIS folders and updated documentation.  
00016 *   
00017 * Version 1.0.2 2010/11/11  
00018 *    Documentation updated.   
00019 *  
00020 * Version 1.0.1 2010/10/05   
00021 *    Production release and review comments incorporated.  
00022 *  
00023 * Version 1.0.0 2010/09/20   
00024 *    Production release and review comments incorporated.  
00025 *  
00026 * Version 0.0.7  2010/06/10   
00027 *    Misra-C changes done  
00028 * -------------------------------------------------------------------- */ 
00029  
00030 #include "arm_math.h" 
00031  
00032 /**  
00033  * @ingroup groupFilters  
00034  */ 
00035  
00036 /**  
00037  * @addtogroup BiquadCascadeDF1_32x64  
00038  * @{  
00039  */ 
00040  
00041 /**  
00042  * @details  
00043  *  
00044  * @param[in,out] *S            points to an instance of the high precision Q31 Biquad cascade filter 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  * @param[in]     postShift     Shift to be applied after the accumulator.  Varies according to the coefficients format.  
00049  * @return        none  
00050  *  
00051  * <b>Coefficient and State Ordering:</b>  
00052  *  
00053  * \par  
00054  * The coefficients are stored in the array <code>pCoeffs</code> in the following order:  
00055  * <pre>  
00056  *     {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}  
00057  * </pre>  
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> points to state variables array and size of each state variable is 1.63 format.  
00064  * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.  
00065  * The state variables are arranged in the state array as:  
00066  * <pre>  
00067  *     {x[n-1], x[n-2], y[n-1], y[n-2]}  
00068  * </pre>  
00069  * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.  
00070  * The state array has a total length of <code>4*numStages</code> values.  
00071  * The state variables are updated after each block of data is processed; the coefficients are untouched.  
00072  */ 
00073  
00074 void arm_biquad_cas_df1_32x64_init_q31 ( 
00075   arm_biquad_cas_df1_32x64_ins_q31 * S, 
00076   uint8_t numStages, 
00077   q31_t * pCoeffs, 
00078   q63_t * pState, 
00079   uint8_t postShift) 
00080 { 
00081   /* Assign filter stages */ 
00082   S->numStages = numStages; 
00083  
00084   /* Assign postShift to be applied to the output */ 
00085   S->postShift = postShift; 
00086  
00087   /* Assign coefficient pointer */ 
00088   S->pCoeffs = pCoeffs; 
00089  
00090   /* Clear state buffer and size is always 4 * numStages */ 
00091   memset(pState, 0, (4u * (uint32_t) numStages) * sizeof(q63_t)); 
00092  
00093   /* Assign state pointer */ 
00094   S->pState = pState; 
00095 } 
00096  
00097 /**  
00098  * @} end of BiquadCascadeDF1_32x64 group  
00099  */