/* ----------------------------------------------------------------------  
* Copyright (C) 2010 ARM Limited. All rights reserved.  
*  
* $Date:        29. November 2010  
* $Revision: 	V1.0.3  
*  
* Project: 	    CMSIS DSP Library  
* Title:	    arm_biquad_cascade_df1_init_q31.c  
*  
* Description:	Q31 Biquad cascade DirectFormI(DF1) filter initialization function.  
*  
*  
* Target Processor: Cortex-M4/Cortex-M3
*  
* Version 1.0.3 2010/11/29 
*    Re-organized the CMSIS folders and updated documentation.  
*   
* Version 1.0.2 2010/11/11  
*    Documentation updated.   
*  
* Version 1.0.1 2010/10/05   
*    Production release and review comments incorporated.  
*  
* Version 1.0.0 2010/09/20   
*    Production release and review comments incorporated.  
*  
* Version 0.0.5  2010/04/26   
* 	 incorporated review comments and updated with latest CMSIS layer  
*  
* Version 0.0.3  2010/03/10   
*    Initial version  
* -------------------------------------------------------------------- */ 
 
#include "arm_math.h" 
 
/**  
 * @ingroup groupFilters  
 */ 
 
/**  
 * @addtogroup BiquadCascadeDF1  
 * @{  
 */ 
 
/**  
 * @details  
 *  
 * @param[in,out] *S           points to an instance of the Q31 Biquad cascade structure.  
 * @param[in]     numStages    number of 2nd order stages in the filter.  
 * @param[in]     *pCoeffs     points to the filter coefficients buffer.  
 * @param[in]     *pState      points to the state buffer.  
 * @param[in]     postShift    Shift to be applied after the accumulator.  Varies according to the coefficients format  
 * @return        none  
 *  
 * <b>Coefficient and State Ordering:</b>  
 *  
 * \par  
 * The coefficients are stored in the array <code>pCoeffs</code> in the following order:  
 * <pre>  
 *     {b10, b11, b12, a11, a12, b20, b21, b22, a21, a22, ...}  
 * </pre>  
 * where <code>b1x</code> and <code>a1x</code> are the coefficients for the first stage,  
 * <code>b2x</code> and <code>a2x</code> are the coefficients for the second stage,  
 * and so on.  The <code>pCoeffs</code> array contains a total of <code>5*numStages</code> values.  
 *  
 * \par  
 * The <code>pState</code> points to state variables array.  
 * Each Biquad stage has 4 state variables <code>x[n-1], x[n-2], y[n-1],</code> and <code>y[n-2]</code>.  
 * The state variables are arranged in the <code>pState</code> array as:  
 * <pre>  
 *     {x[n-1], x[n-2], y[n-1], y[n-2]}  
 * </pre>  
 * The 4 state variables for stage 1 are first, then the 4 state variables for stage 2, and so on.  
 * The state array has a total length of <code>4*numStages</code> values.  
 * The state variables are updated after each block of data is processed; the coefficients are untouched.  
 */ 
 
void arm_biquad_cascade_df1_init_q31( 
  arm_biquad_casd_df1_inst_q31 * S, 
  uint8_t numStages, 
  q31_t * pCoeffs, 
  q31_t * pState, 
  int8_t postShift) 
{ 
  /* Assign filter stages */ 
  S->numStages = numStages; 
 
  /* Assign postShift to be applied to the output */ 
  S->postShift = postShift; 
 
  /* Assign coefficient pointer */ 
  S->pCoeffs = pCoeffs; 
 
  /* Clear state buffer and size is always 4 * numStages */ 
  memset(pState, 0, (4u * (uint32_t) numStages) * sizeof(q31_t)); 
 
  /* Assign state pointer */ 
  S->pState = pState; 
} 
 
/**  
 * @} end of BiquadCascadeDF1 group  
 */