forked from Archive/PX4-Autopilot
109 lines
3.8 KiB
C
109 lines
3.8 KiB
C
/****************************************************************************
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* lib/math/lib_b16atan2.c
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*
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* Copyright (C) 2011 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <fixedmath.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define B16_C1 0x00000373 /* 0.013480470 */
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#define B16_C2 0x00000eb7 /* 0.057477314 */
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#define B16_C3 0x00001f0a /* 0.121239071 */
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#define B16_C4 0x00003215 /* 0.195635925 */
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#define B16_C5 0x0000553f /* 0.332994597 */
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#define B16_C6 0x00010000 /* 0.999995630 */
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#define B16_HALFPI 0x00019220 /* 1.570796327 */
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#define B16_PI 0x00032440 /* 3.141592654 */
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#ifndef MAX
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# define MAX(a,b) (a > b ? a : b)
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#endif
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#ifndef MIN
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# define MIN(a,b) (a < b ? a : b)
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#endif
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#ifndef ABS
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# define ABS(a) (a < 0 ? -a : a)
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#endif
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/****************************************************************************
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* Global Functions
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****************************************************************************/
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/****************************************************************************
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* Name: b16atan2
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*
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* Description:
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* atan2 calculates the arctangent of y/x. (Based on a algorithm I saw
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* posted on the internet... now I have lost the link -- sorry).
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*
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****************************************************************************/
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b16_t b16atan2(b16_t y, b16_t x)
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{
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b16_t t0;
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b16_t t1;
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b16_t t2;
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b16_t t3;
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t2 = ABS(x);
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t1 = ABS(y);
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t0 = MAX(t2, t1);
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t1 = MIN(t2, t1);
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t2 = ub16inv(t0);
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t2 = b16mulb16(t1, t2);
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t3 = b16mulb16(t2, t2);
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t0 = - B16_C1;
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t0 = b16mulb16(t0, t3) + B16_C2;
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t0 = b16mulb16(t0, t3) - B16_C3;
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t0 = b16mulb16(t0, t3) + B16_C4;
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t0 = b16mulb16(t0, t3) - B16_C5;
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t0 = b16mulb16(t0, t3) + B16_C6;
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t2 = b16mulb16(t0, t2);
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t2 = (ABS(y) > ABS(x)) ? B16_HALFPI - t2 : t2;
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t2 = (x < 0) ? B16_PI - t2 : t2;
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t2 = (y < 0) ? -t2 : t2;
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return t2;
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}
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