1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_sin_f32.c
4 * Description: Fast sine calculation for floating-point values
5 *
6 * $Date: 23 April 2021
7 * $Revision: V1.9.0
8 *
9 * Target Processor: Cortex-M and Cortex-A cores
10 * -------------------------------------------------------------------- */
11 /*
12 * Copyright (C) 2010-2021 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 "arm_common_tables.h"
31
32 /**
33 @ingroup groupFastMath
34 */
35
36 /**
37 @defgroup sin Sine
38
39 Computes the trigonometric sine function using a combination of table lookup
40 and linear interpolation. There are separate functions for
41 Q15, Q31, and floating-point data types.
42 The input to the floating-point version is in radians while the
43 fixed-point Q15 and Q31 have a scaled input with the range
44 [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a
45 value of 2*pi wraps around to 0.
46
47 The implementation is based on table lookup using 512 values together with linear interpolation.
48 The steps used are:
49 -# Calculation of the nearest integer table index
50 -# Compute the fractional portion (fract) of the table index.
51 -# The final result equals <code>(1.0f-fract)*a + fract*b;</code>
52
53 where
54 <pre>
55 b = Table[index];
56 c = Table[index+1];
57 </pre>
58 */
59
60 /**
61 @addtogroup sin
62 @{
63 */
64
65 /**
66 @brief Fast approximation to the trigonometric sine function for floating-point data.
67 @param[in] x input value in radians.
68 @return sin(x)
69 */
70
arm_sin_f32(float32_t x)71 float32_t arm_sin_f32(
72 float32_t x)
73 {
74 float32_t sinVal, fract, in; /* Temporary input, output variables */
75 uint16_t index; /* Index variable */
76 float32_t a, b; /* Two nearest output values */
77 int32_t n;
78 float32_t findex;
79
80 /* input x is in radians */
81 /* Scale input to [0 1] range from [0 2*PI] , divide input by 2*pi */
82 in = x * 0.159154943092f;
83
84 /* Calculation of floor value of input */
85 n = (int32_t) in;
86
87 /* Make negative values towards -infinity */
88 if (in < 0.0f)
89 {
90 n--;
91 }
92
93 /* Map input value to [0 1] */
94 in = in - (float32_t) n;
95
96 /* Calculation of index of the table */
97 findex = (float32_t)FAST_MATH_TABLE_SIZE * in;
98 index = (uint16_t)findex;
99
100 /* when "in" is exactly 1, we need to rotate the index down to 0 */
101 if (index >= FAST_MATH_TABLE_SIZE) {
102 index = 0;
103 findex -= (float32_t)FAST_MATH_TABLE_SIZE;
104 }
105
106 /* fractional value calculation */
107 fract = findex - (float32_t) index;
108
109 /* Read two nearest values of input value from the sin table */
110 a = sinTable_f32[index];
111 b = sinTable_f32[index+1];
112
113 /* Linear interpolation process */
114 sinVal = (1.0f - fract) * a + fract * b;
115
116 /* Return output value */
117 return (sinVal);
118 }
119
120 /**
121 @} end of sin group
122 */
123
