1 /* ----------------------------------------------------------------------
2 * Project: CMSIS DSP Library
3 * Title: arm_sin_q31.c
4 * Description: Fast sine calculation for Q31 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 @addtogroup sin
38 @{
39 */
40
41 /**
42 @brief Fast approximation to the trigonometric sine function for Q31 data.
43 @param[in] x Scaled input value in radians
44 @return sin(x)
45
46 The Q31 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*PI).
47 */
48
arm_sin_q31(q31_t x)49 q31_t arm_sin_q31(
50 q31_t x)
51 {
52 q31_t sinVal; /* Temporary variables for input, output */
53 int32_t index; /* Index variable */
54 q31_t a, b; /* Two nearest output values */
55 q31_t fract; /* Temporary values for fractional values */
56
57 if (x < 0)
58 { /* convert negative numbers to corresponding positive ones */
59 x = (uint32_t)x + 0x80000000;
60 }
61
62 /* Calculate the nearest index */
63 index = (uint32_t)x >> FAST_MATH_Q31_SHIFT;
64
65 /* Calculation of fractional value */
66 fract = (x - (index << FAST_MATH_Q31_SHIFT)) << 9;
67
68 /* Read two nearest values of input value from the sin table */
69 a = sinTable_q31[index];
70 b = sinTable_q31[index+1];
71
72 /* Linear interpolation process */
73 sinVal = (q63_t) (0x80000000 - fract) * a >> 32;
74 sinVal = (q31_t) ((((q63_t) sinVal << 32) + ((q63_t) fract * b)) >> 32);
75
76 /* Return output value */
77 return (sinVal << 1);
78 }
79
80 /**
81 @} end of sin group
82 */
83
