109 lines
3.8 KiB
C
109 lines
3.8 KiB
C
/****************************************************************************
|
|
* libc/fixedmath/lib_b16atan2.c
|
|
*
|
|
* Copyright (C) 2011 Gregory Nutt. All rights reserved.
|
|
* Author: Gregory Nutt <gnutt@nuttx.org>
|
|
*
|
|
* 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. Neither the name NuttX nor the names of its contributors may be
|
|
* used to endorse or promote products derived from this software
|
|
* without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
|
|
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
|
|
* COPYRIGHT OWNER OR CONTRIBUTORS 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.
|
|
*
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Included Files
|
|
****************************************************************************/
|
|
|
|
#include <fixedmath.h>
|
|
|
|
/****************************************************************************
|
|
* Pre-processor Definitions
|
|
****************************************************************************/
|
|
|
|
#define B16_C1 0x00000373 /* 0.013480470 */
|
|
#define B16_C2 0x00000eb7 /* 0.057477314 */
|
|
#define B16_C3 0x00001f0a /* 0.121239071 */
|
|
#define B16_C4 0x00003215 /* 0.195635925 */
|
|
#define B16_C5 0x0000553f /* 0.332994597 */
|
|
#define B16_C6 0x00010000 /* 0.999995630 */
|
|
#define B16_HALFPI 0x00019220 /* 1.570796327 */
|
|
#define B16_PI 0x00032440 /* 3.141592654 */
|
|
|
|
#ifndef MAX
|
|
# define MAX(a,b) (a > b ? a : b)
|
|
#endif
|
|
|
|
#ifndef MIN
|
|
# define MIN(a,b) (a < b ? a : b)
|
|
#endif
|
|
|
|
#ifndef ABS
|
|
# define ABS(a) (a < 0 ? -a : a)
|
|
#endif
|
|
|
|
/****************************************************************************
|
|
* Global Functions
|
|
****************************************************************************/
|
|
|
|
/****************************************************************************
|
|
* Name: b16atan2
|
|
*
|
|
* Description:
|
|
* atan2 calculates the arctangent of y/x. (Based on a algorithm I saw
|
|
* posted on the internet... now I have lost the link -- sorry).
|
|
*
|
|
****************************************************************************/
|
|
|
|
b16_t b16atan2(b16_t y, b16_t x)
|
|
{
|
|
b16_t t0;
|
|
b16_t t1;
|
|
b16_t t2;
|
|
b16_t t3;
|
|
|
|
t2 = ABS(x);
|
|
t1 = ABS(y);
|
|
t0 = MAX(t2, t1);
|
|
t1 = MIN(t2, t1);
|
|
t2 = ub16inv(t0);
|
|
t2 = b16mulb16(t1, t2);
|
|
|
|
t3 = b16mulb16(t2, t2);
|
|
t0 = - B16_C1;
|
|
t0 = b16mulb16(t0, t3) + B16_C2;
|
|
t0 = b16mulb16(t0, t3) - B16_C3;
|
|
t0 = b16mulb16(t0, t3) + B16_C4;
|
|
t0 = b16mulb16(t0, t3) - B16_C5;
|
|
t0 = b16mulb16(t0, t3) + B16_C6;
|
|
t2 = b16mulb16(t0, t2);
|
|
|
|
t2 = (ABS(y) > ABS(x)) ? B16_HALFPI - t2 : t2;
|
|
t2 = (x < 0) ? B16_PI - t2 : t2;
|
|
t2 = (y < 0) ? -t2 : t2;
|
|
|
|
return t2;
|
|
}
|