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  
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   */