dsp_fltoq15_c.c

来自「dm642函数库」· C语言 代码 · 共 95 行

/* ======================================================================== */
/*  TEXAS INSTRUMENTS, INC.                                                 */
/*                                                                          */
/*  DSPLIB  DSP Signal Processing Library                                   */
/*                                                                          */
/*  This library contains proprietary intellectual property of Texas        */
/*  Instruments, Inc.  The library and its source code are protected by     */
/*  various copyrights, and portions may also be protected by patents or    */
/*  other legal protections.                                                */
/*                                                                          */
/*  This software is licensed for use with Texas Instruments TMS320         */
/*  family DSPs.  This license was provided to you prior to installing      */
/*  the software.  You may review this license by consulting the file       */
/*  TI_license.PDF which accompanies the files in this library.             */
/* ------------------------------------------------------------------------ */
/*          Copyright (C) 2003 Texas Instruments, Incorporated.             */
/*                          All Rights Reserved.                            */
/* ======================================================================== */


/* ======================================================================= */
/*                                                                         */
/*    TEXAS INSTRUMENTS, INC.                                              */
/*                                                                         */
/*    NAME                                                                 */
/*          DSP_fltoq15                                                    */
/*S                                                                        */
/*                                                                         */
/*    REVISION DATE                                                        */
/*        27-Jul-2001                                                      */
/*                                                                         */
/*  USAGE                                                                  */
/*      This routine is C-callable and can be called as:                   */
/*                                                                         */
/*      void DSP_fltoq15(float x[], short r[], short nx)                   */
/*                                                                         */
/*      x[nx] : Pointer to values of type float                            */
/*      r[nx] : Contains Q15 values from x[nx]                             */
/*      nx    : Number of elements in arrays                               */
/*                                                                         */
/*  DESCRIPTION                                                            */
/*      Convert the IEEE floating point numbers stored in vector x[] into  */
/*      Q.15 format numbers stored in vector r[]. Results are truncated    */
/*      towards zero. Values that exceed the size limit will be saturated  */
/*      to 0x7fff if value is positive and 0x8000 if value is negative.    */
/*      All values too small to be correctly represented will be truncated */
/*      to 0.                                                              */
/*                                                                         */
/*      The 16-bit Q.15 format is defined as follows:                      */
/*                                                                         */
/*          1 11111                                                        */
/*          5 432109876543210                                              */
/*          S.XXXXXXXXXXXXXXX                                              */
/*                                                                         */
/*          range: 1.000000000000000 = -1.0               <-> -32768       */
/*                 0.111111111111111 =  0.999969482421875 <->  32767       */
/*                                                                         */
/*      IEEE floating point format is defined as follows:                  */
/*                                                                         */
/*          31 30....23  22.....0                                          */
/*           S EXPONENT  MANTISSA                                          */
/*                                                                         */
/*      The value is obtained as: (-1)^S * 1.MANTISSA * 2^(EXPONENT-127)   */
/*                                                                         */
/* ----------------------------------------------------------------------- */
/*            Copyright (c) 2003 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================= */

#include <math.h>

void DSP_fltoq15_c(float x[], short r[], short nx)
{
    int i, a;

    for(i = 0; i < nx; i++)
    {
        /* results in saturated integer if overflow */
        a = 32768 * x[i];

        /* saturate to 16-bit */
        if (a>32767)  a =  32767;
        if (a<-32768) a = -32768;

        r[i] = (short) a;
    }
}

/* ======================================================================= */
/*   End of file:  dsp_fltoq15.c                                           */
/* ----------------------------------------------------------------------- */
/*            Copyright (c) 2003 Texas Instruments, Incorporated.           */
/*                           All Rights Reserved.                           */
/* ======================================================================= */