

#include "arm_math.h"

/**    
 * @ingroup groupFilters    
 */

/**    
 * @addtogroup FIR_Interpolate    
 * @{    
 */

/**    
 * @brief  Initialization function for the Q15 FIR interpolator.    
 * @param[in,out] *S        points to an instance of the Q15 FIR interpolator structure.    
 * @param[in]     L         upsample factor.    
 * @param[in]     numTaps   number of filter coefficients in the filter.    
 * @param[in]     *pCoeffs  points to the filter coefficient buffer.    
 * @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    
 * the filter length <code>numTaps</code> is not a multiple of the interpolation factor <code>L</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[numTaps-2], ..., b[1], b[0]}    
 * </pre>    
 * The length of the filter <code>numTaps</code> must be a multiple of the interpolation factor <code>L</code>.    
 * \par    
 * <code>pState</code> points to the array of state variables.    
 * <code>pState</code> is of length <code>(numTaps/L)+blockSize-1</code> words    
 * where <code>blockSize</code> is the number of input samples processed by each call to <code>arm_fir_interpolate_q15()</code>.    
 */

arm_status arm_fir_interpolate_init_q15(
  arm_fir_interpolate_instance_q15 * S,
  uint8_t L,
  uint16_t numTaps,
  q15_t * pCoeffs,
  q15_t * pState,
  uint32_t blockSize)
{
  arm_status status;

  /* The filter length must be a multiple of the interpolation factor */
  if((numTaps % L) != 0u)
  {
    /* Set status as ARM_MATH_LENGTH_ERROR */
    status = ARM_MATH_LENGTH_ERROR;
  }
  else
  {

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

    /* Assign Interpolation factor */
    S->L = L;

    /* Assign polyPhaseLength */
    S->phaseLength = numTaps / L;

    /* Clear state buffer and size of buffer is always phaseLength + blockSize - 1 */
    memset(pState, 0,
           (blockSize + ((uint32_t) S->phaseLength - 1u)) * sizeof(q15_t));

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

    status = ARM_MATH_SUCCESS;
  }

  return (status);

}

 /**    
  * @} end of FIR_Interpolate group    
  */
