text: /*****************************************************************************
   *
   * \file
   *
   * \brief Generic 16-bit NLMS filter function.
   *
   * This file contains the code of the NLMS filter.
   *
   * Copyright (c) 2014 Atmel Corporation. All rights reserved.
   *
   * \asf_license_start
   *
   * \page License
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice,
   *    this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright notice,
   *    this list of conditions and the following disclaimer in the documentation
   *    and/or other materials provided with the distribution.
   *
   * 3. The name of Atmel may not be used to endorse or promote products derived
   *    from this software without specific prior written permission.
   *
   * 4. This software may only be redistributed and used in connection with an
   *    Atmel microcontroller product.
   *
   * THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
   * EXPRESSLY AND SPECIFICALLY DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR
   * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGE.
   *
   * \asf_license_stop
   *
   *****************************************************************************/
   /**
   * Support and FAQ: visit <a href="http://www.atmel.com/design-support/">Atmel Support</a>
   */
  
  
  #include "dsp.h"
  
  #if defined(FORCE_ALL_GENERICS) || \
      defined(FORCE_GENERIC_FILT16_NLMS) || \
      !defined(TARGET_SPECIFIC_FILT16_NLMS)
  
  #include "filt_nlms.h"
  
  void dsp16_filt_nlms(dsp16_t *x, dsp16_t *w, int size, dsp16_t new_x, dsp16_t d, dsp16_t *y, dsp16_t *e)
  {
    int i;
    static S32 normalization = 0;
    S32 temp;
  
    x[0] = new_x;
  
    temp = 0;
    // Performed a FIR
    for(i=0; i<size; i+=4)
    {
      temp += (((S32) w[i])*((S32) x[i]));
      temp += (((S32) w[i+1])*((S32) x[i+1]));
      temp += (((S32) w[i+2])*((S32) x[i+2]));
      temp += (((S32) w[i+3])*((S32) x[i+3]));
    }
    *y = temp >> (DSP16_QB);
  
    // Error calculation
    *e = d - *y;
  
    // Update the normalization coefficient
    normalization += ((((S32) new_x)*((S32) new_x))) >> (DSP16_QB);
  
  
    if (!normalization)
      normalization = 1;
  
  #if !(DSP_OPTIMIZATION & DSP_OPTI_ACCURACY)
    temp = ((S32) *e << DSP16_QB)/normalization;
    if (temp > 0x7FFF)
      temp = 0x7FFF;
    else if (temp < -0x8000)
      temp = -0x8000;
  #endif
  
    // Refresh the w coefficients
    for(i=0; i<size; i+=4)
    {
  #if (DSP_OPTIMIZATION & DSP_OPTI_ACCURACY)
      w[i] += ((((((S32) *e)*((S32) x[i])))/normalization) >> (DSP_NLMS_MU - 1));
      w[i+1] += ((((((S32) *e)*((S32) x[i+1])))/normalization) >> (DSP_NLMS_MU - 1));
      w[i+2] += ((((((S32) *e)*((S32) x[i+2])))/normalization) >> (DSP_NLMS_MU - 1));
      w[i+3] += ((((((S32) *e)*((S32) x[i+3])))/normalization) >> (DSP_NLMS_MU - 1));
  #else
      w[i] += (temp*((S32) x[i])) >> (DSP_NLMS_MU - 1 + DSP16_QB);
      w[i+1] += (temp*((S32) x[i+1])) >> (DSP_NLMS_MU - 1 + DSP16_QB);
      w[i+2] += (temp*((S32) x[i+2])) >> (DSP_NLMS_MU - 1 + DSP16_QB);
      w[i+3] += (temp*((S32) x[i+3])) >> (DSP_NLMS_MU - 1 + DSP16_QB);
  #endif
    }
  
    // Update the normalization coefficient
    normalization -= ((((S32) x[size-1])*((S32) x[size-1]))) >> (DSP16_QB);
  
    // Shift the circular buffer
    for(i=size-1; i>0; i-=4)
    {
      x[i] = x[i-1];
      x[i-1] = x[i-2];
      x[i-2] = x[i-3];
      x[i-3] = x[i-4];
    }
  }
  
  #endif
  
  