ti/dsplib/src/DSP_fir_r8/c64P/DSP_fir_r8_cn.c

   1 /* ======================================================================= */
   2 /* DSP_fir_r8_cn.c -- FIR Filter (Radix 8)                                 */
   3 /*                    Natural C Implementation                             */
   4 /*                                                                         */
   5 /* Rev 0.0.1                                                               */
   6 /*                                                                         */
   7 /*  Usage                                                                  */
   8 /*     This routine is C-callable and can be called as:                    */
   9 /*                                                                         */
  10 /*     void DSP_fir_r8_cn (                                                */
  11 /*         const short *restrict x,                                        */
  12 /*         const short *restrict h,                                        */
  13 /*         short *restrict r,                                              */
  14 /*         int nh,                                                         */
  15 /*         int nr,                                                         */
  16 /*     )                                                                   */
  17 /*                                                                         */
  18 /*  Description                                                            */
  19 /*     Computes a real FIR filter (direct-form) using coefficients         */
  20 /*     stored in vector h.  The real data input is stored in vector x.     */
  21 /*     The filter output result is stored in vector r.  Input data and     */
  22 /*     filter taps are 16-bit, with intermediate values kept at 32-bit     */
  23 /*     precision.  Filter taps are expected in Q15 format.                 */
  24 /*                                                                         */
  25 /*  Assumptions                                                            */
  26 /*     Arrays x, h, and r do not overlap                                   */
  27 /*                                                                         */
  28 /* Copyright (C) 2011 Texas Instruments Incorporated - http://www.ti.com/  */
  29 /*                                                                         */
  30 /*                                                                         */
  31 /*  Redistribution and use in source and binary forms, with or without     */
  32 /*  modification, are permitted provided that the following conditions     */
  33 /*  are met:                                                               */
  34 /*                                                                         */
  35 /*    Redistributions of source code must retain the above copyright       */
  36 /*    notice, this list of conditions and the following disclaimer.        */
  37 /*                                                                         */
  38 /*    Redistributions in binary form must reproduce the above copyright    */
  39 /*    notice, this list of conditions and the following disclaimer in the  */
  40 /*    documentation and/or other materials provided with the               */
  41 /*    distribution.                                                        */
  42 /*                                                                         */
  43 /*    Neither the name of Texas Instruments Incorporated nor the names of  */
  44 /*    its contributors may be used to endorse or promote products derived  */
  45 /*    from this software without specific prior written permission.        */
  46 /*                                                                         */
  47 /*  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS    */
  48 /*  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT      */
  49 /*  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR  */
  50 /*  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT   */
  51 /*  OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,  */
  52 /*  SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT       */
  53 /*  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,  */
  54 /*  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY  */
  55 /*  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT    */
  56 /*  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE  */
  57 /*  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.   */
  58 /*                                                                         */
  59 /* ======================================================================= */
  60
  61 #pragma CODE_SECTION(DSP_fir_r8_cn, ".text:ansi");
  62
  63 #include "DSP_fir_r8_cn.h"
  64
  65 void DSP_fir_r8_cn (
  66     const short *restrict x,    /* Input array [nr+nh-1 elements] */
  67     const short *restrict h,    /* Coeff array [nh elements]      */
  68     short       *restrict r,    /* Output array [nr elements]     */
  69     int nh,                     /* Number of coefficients         */
  70     int nr                      /* Number of output samples       */
  71 )
  72 {
  73     int i, j, sum;
  74
  75 #ifndef NOASSUME
  76     _nassert(nr % 4 == 0);
  77     _nassert(nr >= 4);
  78 #endif
  79     for (j = 0; j < nr; j++) {
  80         sum = 0;
  81 #ifndef NOASSUME
  82         _nassert(nh % 8 == 0);
  83         _nassert(nh >= 8);
  84 #endif
  85         for (i = 0; i < nh; i++)
  86             sum += x[i + j] * h[i];
  87         r[j] = sum >> 15;
  88     }
  89 }
  90
  91 /* ======================================================================= */
  92 /*  End of file:  DSP_fir_r8_cn.c                                          */
  93 /* ----------------------------------------------------------------------- */
  94 /*            Copyright (c) 2011 Texas Instruments, Incorporated.          */
  95 /*                           All Rights Reserved.                          */
  96 /* ======================================================================= */
  97