1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_atan2_q15.c
4 * Description: q15 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 #include "dsp/utils.h"
31
32 /*
33
34 atan for argument between in [0, 1.0]
35
36 */
37
38
39 /* Q2.13 */
40 #define ATANHALFQ13 0xed6
41 #define PIHALFQ13 0x3244
42 #define PIQ13 0x6488
43
44 #define ATAN2_NB_COEFS_Q15 10
45
46 static const q15_t atan2_coefs_q15[ATAN2_NB_COEFS_Q15]={
47 0, // 0x0000
48 32767, // 0x7fff
49 -1, // 0xffff
50 -10905, // 0xd567
51 -144, // 0xff70
52 7085, // 0x1bad
53 -680, // 0xfd58
54 -5719, // 0xe9a9
55 4393, // 0x1129
56 -1061 // 0xfbdb
57 };
58
arm_atan_limited_q15(q15_t x)59 __STATIC_FORCEINLINE q15_t arm_atan_limited_q15(q15_t x)
60 {
61 q31_t res=(q31_t)atan2_coefs_q15[ATAN2_NB_COEFS_Q15-1];
62 int i=1;
63 for(i=1;i<ATAN2_NB_COEFS_Q15;i++)
64 {
65 res = ((q31_t) x * res) >> 15U;
66 res = res + ((q31_t) atan2_coefs_q15[ATAN2_NB_COEFS_Q15-1-i]) ;
67 }
68
69 res = __SSAT(res>>2,16);
70
71
72 return(res);
73 }
74
75
arm_atan_q15(q15_t y,q15_t x)76 __STATIC_FORCEINLINE q15_t arm_atan_q15(q15_t y,q15_t x)
77 {
78 int sign=0;
79 q15_t res=0;
80
81 if (y<0)
82 {
83 /* Negate y */
84 #if defined (ARM_MATH_DSP)
85 y = __QSUB16(0, y);
86 #else
87 y = (y == (q15_t) 0x8000) ? (q15_t) 0x7fff : -y;
88 #endif
89
90 sign=1-sign;
91 }
92
93 if (x < 0)
94 {
95 sign=1 - sign;
96
97 /* Negate x */
98 #if defined (ARM_MATH_DSP)
99 x = __QSUB16(0, x);
100 #else
101 x = (x == (q15_t) 0x8000) ? (q15_t) 0x7fff : -x;
102 #endif
103 }
104
105 if (y > x)
106 {
107 q15_t ratio;
108 int16_t shift;
109
110 arm_divide_q15(x,y,&ratio,&shift);
111
112 /* Shift ratio by shift */
113 if (shift >=0)
114 {
115 ratio = __SSAT(((q31_t) ratio << shift), 16);
116 }
117 else
118 {
119 ratio = (ratio >> -shift);
120 }
121
122 res = PIHALFQ13 - arm_atan_limited_q15(ratio);
123
124 }
125 else
126 {
127 q15_t ratio;
128 int16_t shift;
129
130 arm_divide_q15(y,x,&ratio,&shift);
131
132 /* Shift ratio by shift */
133 if (shift >=0)
134 {
135 ratio = __SSAT(((q31_t) ratio << shift), 16);
136 }
137 else
138 {
139 ratio = (ratio >> -shift);
140 }
141
142
143 res = arm_atan_limited_q15(ratio);
144
145 }
146
147
148 if (sign)
149 {
150 /* Negate res */
151 #if defined (ARM_MATH_DSP)
152 res = __QSUB16(0, res);
153 #else
154 res = (res == (q15_t) 0x8000) ? (q15_t) 0x7fff : -res;
155 #endif
156 }
157
158 return(res);
159 }
160
161
162 /**
163 @ingroup groupFastMath
164 */
165
166
167 /**
168 @addtogroup atan2
169 @{
170 */
171
172 /**
173 @brief Arc Tangent of y/x using sign of y and x to get right quadrant
174 @param[in] y y coordinate
175 @param[in] x x coordinate
176 @param[out] result Result in Q2.13
177 @return error status.
178
179 @par Compute the Arc tangent of y/x:
180 The sign of y and x are used to determine the right quadrant
181 and compute the right angle. Returned value is between -Pi and Pi.
182 */
183
184
arm_atan2_q15(q15_t y,q15_t x,q15_t * result)185 ARM_DSP_ATTRIBUTE arm_status arm_atan2_q15(q15_t y,q15_t x,q15_t *result)
186 {
187 if (x > 0)
188 {
189 *result=arm_atan_q15(y,x);
190 return(ARM_MATH_SUCCESS);
191 }
192 if (x < 0)
193 {
194 if (y > 0)
195 {
196 *result=arm_atan_q15(y,x) + PIQ13;
197 }
198 else if (y < 0)
199 {
200 *result=arm_atan_q15(y,x) - PIQ13;
201 }
202 else
203 {
204 *result= PIQ13;
205 }
206 return(ARM_MATH_SUCCESS);
207 }
208 if (x == 0)
209 {
210 if (y > 0)
211 {
212 *result=PIHALFQ13;
213 return(ARM_MATH_SUCCESS);
214 }
215 if (y < 0)
216 {
217 *result=-PIHALFQ13;
218 return(ARM_MATH_SUCCESS);
219 }
220 }
221
222
223 return(ARM_MATH_NANINF);
224
225 }
226
227 /**
228 @} end of atan2 group
229 */
230
