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  
 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   */