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  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.  */
  124.