diff options
Diffstat (limited to 'nuttx/lib/math/lib_b16atan2.c')
-rw-r--r-- | nuttx/lib/math/lib_b16atan2.c | 108 |
1 files changed, 108 insertions, 0 deletions
diff --git a/nuttx/lib/math/lib_b16atan2.c b/nuttx/lib/math/lib_b16atan2.c new file mode 100644 index 000000000..a39652451 --- /dev/null +++ b/nuttx/lib/math/lib_b16atan2.c @@ -0,0 +1,108 @@ +/**************************************************************************** + * lib/math/lib_b16atan2.c + * + * Copyright (C) 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * + * 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; +} |