1  /* ----------------------------------------------------------------------
 2   * Project:      CMSIS DSP Library
 3   * Title:        arm_sin_q15.c
 4   * Description:  Fast sine calculation for Q15 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 Q15 data.
43    @param[in]     x  Scaled input value in radians
44    @return        sin(x)
45  
46    The Q15 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  q15_t arm_sin_q15(
50    q15_t x)
51  {
52    q15_t sinVal;                                  /* Temporary input, output variables */
53    int32_t index;                                 /* Index variable */
54    q15_t a, b;                                    /* Two nearest output values */
55    q15_t fract;                                   /* Temporary values for fractional values */
56  
57    
58    if (x < 0)
59    { /* convert negative numbers to corresponding positive ones */
60      x = (uint16_t)x + 0x8000;
61    }
62  
63    /* Calculate the nearest index */
64    index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
65  
66    /* Calculation of fractional value */
67    fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
68  
69    /* Read two nearest values of input value from the sin table */
70    a = sinTable_q15[index];
71    b = sinTable_q15[index+1];
72  
73    /* Linear interpolation process */
74    sinVal = (q31_t) (0x8000 - fract) * a >> 16;
75    sinVal = (q15_t) ((((q31_t) sinVal << 16) + ((q31_t) fract * b)) >> 16);
76  
77    /* Return output value */
78    return (sinVal << 1);
79  }
80  
81  /**
82    @} end of sin group
83   */