lib/main/CMSIS/DSP/Source/FastMathFunctions/arm_sin_f32.c

   1 /* ----------------------------------------------------------------------
   2  * Project:      CMSIS DSP Library
   3  * Title:        arm_sin_f32.c
   4  * Description:  Fast sine calculation for floating-point values
   5  *
   6  * $Date:        27. January 2017
   7  * $Revision:    V.1.5.1
   8  *
   9  * Target Processor: Cortex-M cores
  10  * -------------------------------------------------------------------- */
  11 /*
  12  * Copyright (C) 2010-2017 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 "arm_math.h"
  30 #include "arm_common_tables.h"
  31 #include <math.h>
  32
  33 /**
  34  * @ingroup groupFastMath
  35  */
  36
  37 /**
  38  * @defgroup sin Sine
  39  *
  40  * Computes the trigonometric sine function using a combination of table lookup
  41  * and linear interpolation.  There are separate functions for
  42  * Q15, Q31, and floating-point data types.
  43  * The input to the floating-point version is in radians and in the range [0 2*pi) while the
  44  * fixed-point Q15 and Q31 have a scaled input with the range
  45  * [0 +0.9999] mapping to [0 2*pi).  The fixed-point range is chosen so that a
  46  * value of 2*pi wraps around to 0.
  47  *
  48  * The implementation is based on table lookup using 256 values together with linear interpolation.
  49  * The steps used are:
  50  *  -# Calculation of the nearest integer table index
  51  *  -# Compute the fractional portion (fract) of the table index.
  52  *  -# The final result equals <code>(1.0f-fract)*a + fract*b;</code>
  53  *
  54  * where
  55  * <pre>
  56  *    b=Table[index+0];
  57  *    c=Table[index+1];
  58  * </pre>
  59  */
  60
  61 /**
  62  * @addtogroup sin
  63  * @{
  64  */
  65
  66 /**
  67  * @brief  Fast approximation to the trigonometric sine function for floating-point data.
  68  * @param[in] x input value in radians.
  69  * @return  sin(x).
  70  */
  71
  72 float32_t arm_sin_f32(
  73   float32_t x)
  74 {
  75   float32_t sinVal, fract, in;                           /* Temporary variables for input, output */
  76   uint16_t index;                                        /* Index variable */
  77   float32_t a, b;                                        /* Two nearest output values */
  78   int32_t n;
  79   float32_t findex;
  80
  81   /* Special case for small negative inputs */
  82   if ((x < 0.0f) && (x >= -1.9e-7f)) {
  83      return x;
  84   }
  85
  86   /* input x is in radians */
  87   /* Scale the input to [0 1] range from [0 2*PI] , divide input by 2*pi */
  88   in = x * 0.159154943092f;
  89
  90   /* Calculation of floor value of input */
  91   n = (int32_t) in;
  92
  93   /* Make negative values towards -infinity */
  94   if (x < 0.0f)
  95   {
  96     n--;
  97   }
  98
  99   /* Map input value to [0 1] */
 100   in = in - (float32_t) n;
 101
 102   /* Calculation of index of the table */
 103   findex = (float32_t) FAST_MATH_TABLE_SIZE * in;
 104
 105   index = ((uint16_t)findex) & 0x1ff;
 106
 107   /* fractional value calculation */
 108   fract = findex - (float32_t) index;
 109
 110   /* Read two nearest values of input value from the sin table */
 111   a = sinTable_f32[index];
 112   b = sinTable_f32[index+1];
 113
 114   /* Linear interpolation process */
 115   sinVal = (1.0f-fract)*a + fract*b;
 116
 117   /* Return the output value */
 118   return (sinVal);
 119 }
 120
 121 /**
 122  * @} end of sin group
 123  */