hardware/arduino/sam/system/CMSIS/CMSIS/DSP_Lib/Source/FilteringFunctions/arm_fir_decimate_init_q31.c

/* ----------------------------------------------------------------------   
* Copyright (C) 2010 ARM Limited. All rights reserved.   
*   
* $Date:        15. July 2011  
* $Revision: 	V1.0.10  
*   
* Project: 	    CMSIS DSP Library   
* Title:        arm_fir_decimate_init_q31.c   
*   
* Description:  Initialization function for Q31 FIR Decimation filter.   
*   
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*  
* Version 1.0.10 2011/7/15 
*    Big Endian support added and Merged M0 and M3/M4 Source code.  
*   
* 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 0.0.7  2010/06/10    
*    Misra-C changes done   
* ------------------------------------------------------------------- */

#include "arm_math.h"

/**   
 * @ingroup groupFilters   
 */

/**   
 * @addtogroup FIR_decimate   
 * @{   
 */

/**   
 * @brief  Initialization function for the Q31 FIR decimator.   
 * @param[in,out] *S points to an instance of the Q31 FIR decimator structure.   
 * @param[in] numTaps  number of coefficients in the filter.   
 * @param[in] M  decimation factor.   
 * @param[in] *pCoeffs points to the filter coefficients.   
 * @param[in] *pState points to the state buffer.   
 * @param[in] blockSize number of input samples to process per call.   
 * @return    The function returns ARM_MATH_SUCCESS if initialization was successful or ARM_MATH_LENGTH_ERROR if   
 * <code>blockSize</code> is not a multiple of <code>M</code>.   
 *   
 * <b>Description:</b>   
 * \par   
 * <code>pCoeffs</code> points to the array of filter coefficients stored in time reversed order:   
 * <pre>   
 *    {b[numTaps-1], b[numTaps-2], b[N-2], ..., b[1], b[0]}   
 * </pre>   
 * \par   
 * <code>pState</code> points to the array of state variables.   
 * <code>pState</code> is of length <code>numTaps+blockSize-1</code> words where <code>blockSize</code> is the number of input samples passed to <code>arm_fir_decimate_q31()</code>.   
 * <code>M</code> is the decimation factor.   
 */

arm_status arm_fir_decimate_init_q31(
  arm_fir_decimate_instance_q31 * S,
  uint16_t numTaps,
  uint8_t M,
  q31_t * pCoeffs,
  q31_t * pState,
  uint32_t blockSize)
{
  arm_status status;

  /* The size of the input block must be a multiple of the decimation factor */
  if((blockSize % M) != 0u)
  {
    /* Set status as ARM_MATH_LENGTH_ERROR */
    status = ARM_MATH_LENGTH_ERROR;
  }
  else
  {
    /* Assign filter taps */
    S->numTaps = numTaps;

    /* Assign coefficient pointer */
    S->pCoeffs = pCoeffs;

    /* Clear the state buffer.  The size is always (blockSize + numTaps - 1) */
    memset(pState, 0, (numTaps + (blockSize - 1)) * sizeof(q31_t));

    /* Assign state pointer */
    S->pState = pState;

    /* Assign Decimation factor */
    S->M = M;

    status = ARM_MATH_SUCCESS;
  }

  return (status);

}

/**   
 * @} end of FIR_decimate group   
 */