lib/main/CMSIS/DSP/Source/FastMathFunctions/arm_sin_q31.c

   1 /* ----------------------------------------------------------------------
   2  * Project:      CMSIS DSP Library
   3  * Title:        arm_sin_q31.c
   4  * Description:  Fast sine calculation for Q31 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 groupFastMath
  34  */
  35
  36  /**
  37  * @addtogroup sin
  38  * @{
  39  */
  40
  41 /**
  42  * @brief Fast approximation to the trigonometric sine function for Q31 data.
  43  * @param[in] x Scaled input value in radians.
  44  * @return  sin(x).
  45  *
  46  * The Q31 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi). */
  47
  48 q31_t arm_sin_q31(
  49   q31_t x)
  50 {
  51   q31_t sinVal;                                  /* Temporary variables for input, output */
  52   int32_t index;                                 /* Index variables */
  53   q31_t a, b;                                    /* Four nearest output values */
  54   q31_t fract;                                   /* Temporary values for fractional values */
  55
  56   /* Calculate the nearest index */
  57   index = (uint32_t)x >> FAST_MATH_Q31_SHIFT;
  58
  59   /* Calculation of fractional value */
  60   fract = (x - (index << FAST_MATH_Q31_SHIFT)) << 9;
  61
  62   /* Read two nearest values of input value from the sin table */
  63   a = sinTable_q31[index];
  64   b = sinTable_q31[index+1];
  65
  66   /* Linear interpolation process */
  67   sinVal = (q63_t)(0x80000000-fract)*a >> 32;
  68   sinVal = (q31_t)((((q63_t)sinVal << 32) + ((q63_t)fract*b)) >> 32);
  69
  70   return sinVal << 1;
  71 }
  72
  73 /**
  74  * @} end of sin group
  75  */