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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_sin_cos_f32.c
  4.  * Description:  Sine and Cosine 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.  
  32. /**
  33.  * @ingroup groupController
  34.  */
  35.  
  36. /**
  37.  * @defgroup SinCos Sine Cosine
  38.  *
  39.  * Computes the trigonometric sine and cosine values using a combination of table lookup
  40.  * and linear interpolation.
  41.  * There are separate functions for Q31 and floating-point data types.
  42.  * The input to the floating-point version is in degrees while the
  43.  * fixed-point Q31 have a scaled input with the range
  44.  * [-1 0.9999] mapping to [-180 +180] degrees.
  45.  *
  46.  * The floating point function also allows values that are out of the usual range. When this happens, the function will
  47.  * take extra time to adjust the input value to the range of [-180 180].
  48.  *
  49.  * The result is accurate to 5 digits after the decimal point.
  50.  *
  51.  * The implementation is based on table lookup using 360 values together with linear interpolation.
  52.  * The steps used are:
  53.  *  -# Calculation of the nearest integer table index.
  54.  *  -# Compute the fractional portion (fract) of the input.
  55.  *  -# Fetch the value corresponding to \c index from sine table to \c y0 and also value from \c index+1 to \c y1.
  56.  *  -# Sine value is computed as <code> *psinVal = y0 + (fract * (y1 - y0))</code>.
  57.  *  -# Fetch the value corresponding to \c index from cosine table to \c y0 and also value from \c index+1 to \c y1.
  58.  *  -# Cosine value is computed as <code> *pcosVal = y0 + (fract * (y1 - y0))</code>.
  59.  */
  60.  
  61.  /**
  62.  * @addtogroup SinCos
  63.  * @{
  64.  */
  65.  
  66. /**
  67.  * @brief  Floating-point sin_cos function.
  68.  * @param[in]  theta    input value in degrees
  69.  * @param[out] *pSinVal points to the processed sine output.
  70.  * @param[out] *pCosVal points to the processed cos output.
  71.  * @return none.
  72.  */
  73.  
  74. void arm_sin_cos_f32(
  75.                       float32_t theta,
  76.                       float32_t * pSinVal,
  77.                       float32_t * pCosVal)
  78. {
  79.     float32_t fract, in;                             /* Temporary variables for input, output */
  80.     uint16_t indexS, indexC;                         /* Index variable */
  81.     float32_t f1, f2, d1, d2;                        /* Two nearest output values */
  82.     float32_t findex, Dn, Df, temp;
  83.  
  84.     /* input x is in degrees */
  85.     /* Scale the input, divide input by 360, for cosine add 0.25 (pi/2) to read sine table */
  86.     in = theta * 0.00277777777778f;
  87.  
  88.     if (in < 0.0f)
  89.     {
  90.         in = -in;
  91.     }
  92.  
  93.     in = in - (int32_t)in;
  94.  
  95.     /* Calculation of index of the table */
  96.     findex = (float32_t) FAST_MATH_TABLE_SIZE * in;
  97.     indexS = ((uint16_t)findex) & 0x1ff;
  98.     indexC = (indexS + (FAST_MATH_TABLE_SIZE / 4)) & 0x1ff;
  99.  
  100.     /* fractional value calculation */
  101.     fract = findex - (float32_t) indexS;
  102.  
  103.     /* Read two nearest values of input value from the cos & sin tables */
  104.     f1 = sinTable_f32[indexC+0];
  105.     f2 = sinTable_f32[indexC+1];
  106.     d1 = -sinTable_f32[indexS+0];
  107.     d2 = -sinTable_f32[indexS+1];
  108.  
  109.     temp = (1.0f - fract) * f1 + fract * f2;
  110.  
  111.     Dn = 0.0122718463030f; // delta between the two points (fixed), in this case 2*pi/FAST_MATH_TABLE_SIZE
  112.     Df = f2 - f1;          // delta between the values of the functions
  113.  
  114.     temp = Dn *(d1 + d2) - 2 * Df;
  115.     temp = fract * temp + (3 * Df - (d2 + 2 * d1) * Dn);
  116.     temp = fract * temp + d1 * Dn;
  117.  
  118.     /* Calculation of cosine value */
  119.     *pCosVal = fract * temp + f1;
  120.  
  121.     /* Read two nearest values of input value from the cos & sin tables */
  122.     f1 = sinTable_f32[indexS+0];
  123.     f2 = sinTable_f32[indexS+1];
  124.     d1 = sinTable_f32[indexC+0];
  125.     d2 = sinTable_f32[indexC+1];
  126.  
  127.     temp = (1.0f - fract) * f1 + fract * f2;
  128.  
  129.     Df = f2 - f1; // delta between the values of the functions
  130.     temp = Dn*(d1 + d2) - 2*Df;
  131.     temp = fract*temp + (3*Df - (d2 + 2*d1)*Dn);
  132.     temp = fract*temp + d1*Dn;
  133.  
  134.     /* Calculation of sine value */
  135.     *pSinVal = fract*temp + f1;
  136.  
  137.     if (theta < 0.0f)
  138.     {
  139.         *pSinVal = -*pSinVal;
  140.     }
  141. }
  142. /**
  143.  * @} end of SinCos group
  144.  */
  145.