1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_atan2_f32.c
4 * Description: float32 Arc tangent of y/x
5 *
6 * $Date: 22 April 2022
7 * $Revision: V1.10.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2022 ARM Limited or its affiliates. All rights reserved.
13 *
14 * SPDX-License-Identifier: Apache-2.0
15 *
16 * Licensed under the Apache License, Version 2.0 (the License); you may
17 * not use this file except in compliance with the License.
18 * You may obtain a copy of the License at
19 *
20 * www.apache.org/licenses/LICENSE-2.0
21 *
22 * Unless required by applicable law or agreed to in writing, software
23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
25 * See the License for the specific language governing permissions and
26 * limitations under the License.
27 */
28
29 #include "dsp/fast_math_functions.h"
30
31 /*
32
33 atan for argument between in [0, 1.0]
34
35
36 */
37
38 #define ATANHALFF32 0.463648f
39 #define PIHALFF32 1.5707963267948966192313f
40
41 #define ATAN2_NB_COEFS_F32 10
42
43 static const float32_t atan2_coefs_f32[ATAN2_NB_COEFS_F32]={0.0f
44 ,1.0000001638308195518f
45 ,-0.0000228941363602264f
46 ,-0.3328086544578890873f
47 ,-0.004404814619311061f
48 ,0.2162217461808173258f
49 ,-0.0207504842057097504f
50 ,-0.1745263362250363339f
51 ,0.1340557235283553386f
52 ,-0.0323664125927477625f
53 };
54
arm_atan_limited_f32(float32_t x)55 __STATIC_FORCEINLINE float32_t arm_atan_limited_f32(float32_t x)
56 {
57 float32_t res=atan2_coefs_f32[ATAN2_NB_COEFS_F32-1];
58 int i=1;
59 for(i=1;i<ATAN2_NB_COEFS_F32;i++)
60 {
61 res = x*res + atan2_coefs_f32[ATAN2_NB_COEFS_F32-1-i];
62 }
63
64
65 return(res);
66 }
67
arm_atan_f32(float32_t x)68 __STATIC_FORCEINLINE float32_t arm_atan_f32(float32_t x)
69 {
70 int sign=0;
71 float32_t res=0.0f;
72
73 if (x < 0.0f)
74 {
75 sign=1;
76 x=-x;
77 }
78
79 if (x > 1.0f)
80 {
81 x = 1.0f / x;
82 res = PIHALFF32 - arm_atan_limited_f32(x);
83 }
84 else
85 {
86 res += arm_atan_limited_f32(x);
87 }
88
89
90 if (sign)
91 {
92 res = -res;
93 }
94
95 return(res);
96 }
97
98
99 /**
100 @ingroup groupFastMath
101 */
102
103 /**
104 @defgroup atan2 ArcTan2
105
106 Computing Arc tangent only using the ratio y/x is not enough to determine the angle
107 since there is an indeterminacy. Opposite quadrants are giving the same ratio.
108
109 ArcTan2 is not using y/x to compute the angle but y and x and use the sign of y and x
110 to determine the quadrant.
111
112 */
113
114 /**
115 @addtogroup atan2
116 @{
117 */
118
119 /**
120 @brief Arc Tangent of y/x using sign of y and x to get right quadrant
121 @param[in] y y coordinate
122 @param[in] x x coordinate
123 @param[out] result Result
124 @return error status.
125
126 @par Compute the Arc tangent of y/x:
127 The sign of y and x are used to determine the right quadrant
128 and compute the right angle. Returned value is between -Pi and Pi.
129 */
130
131
arm_atan2_f32(float32_t y,float32_t x,float32_t * result)132 ARM_DSP_ATTRIBUTE arm_status arm_atan2_f32(float32_t y,float32_t x,float32_t *result)
133 {
134 if (x > 0.0f)
135 {
136 *result=arm_atan_f32(y/x);
137 return(ARM_MATH_SUCCESS);
138 }
139 if (x < 0.0f)
140 {
141 if (y > 0.0f)
142 {
143 *result=arm_atan_f32(y/x) + PI;
144 }
145 else if (y < 0.0f)
146 {
147 *result=arm_atan_f32(y/x) - PI;
148 }
149 else
150 {
151 if (signbit(y))
152 {
153 *result= -PI;
154 }
155 else
156 {
157 *result= PI;
158 }
159 }
160 return(ARM_MATH_SUCCESS);
161 }
162 if (x == 0.0f)
163 {
164 if (y > 0.0f)
165 {
166 *result=PIHALFF32;
167 return(ARM_MATH_SUCCESS);
168 }
169 if (y < 0.0f)
170 {
171 *result=-PIHALFF32;
172 return(ARM_MATH_SUCCESS);
173 }
174 }
175
176
177 return(ARM_MATH_NANINF);
178
179 }
180
181 /**
182 @} end of atan2 group
183 */
184
