arm_sin_q15.c

00001 /* ----------------------------------------------------------------------
00002  * Project:      CMSIS DSP Library
00003  * Title:        arm_sin_q15.c
00004  * Description:  Fast sine calculation for Q15 values
00005  *
00006  * $Date:        27. January 2017
00007  * $Revision:    V.1.5.1
00008  *
00009  * Target Processor: Cortex-M cores
00010  * -------------------------------------------------------------------- */
00011 /*
00012  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
00013  *
00014  * SPDX-License-Identifier: Apache-2.0
00015  *
00016  * Licensed under the Apache License, Version 2.0 (the License); you may
00017  * not use this file except in compliance with the License.
00018  * You may obtain a copy of the License at
00019  *
00020  * www.apache.org/licenses/LICENSE-2.0
00021  *
00022  * Unless required by applicable law or agreed to in writing, software
00023  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00024  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00025  * See the License for the specific language governing permissions and
00026  * limitations under the License.
00027  */
00028 
00029 #include "arm_math.h"
00030 #include "arm_common_tables.h"
00031 
00032 /**
00033  * @ingroup groupFastMath
00034  */
00035 
00036  /**
00037  * @addtogroup sin
00038  * @{
00039  */
00040 
00041 /**
00042  * @brief Fast approximation to the trigonometric sine function for Q15 data.
00043  * @param[in] x Scaled input value in radians.
00044  * @return  sin(x).
00045  *
00046  * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi).
00047  */
00048 
00049 q15_t arm_sin_q15(
00050   q15_t x)
00051 {
00052   q15_t sinVal;                                  /* Temporary variables for input, output */
00053   int32_t index;                                 /* Index variables */
00054   q15_t a, b;                                    /* Four nearest output values */
00055   q15_t fract;                                   /* Temporary values for fractional values */
00056 
00057   /* Calculate the nearest index */
00058   index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
00059 
00060   /* Calculation of fractional value */
00061   fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
00062 
00063   /* Read two nearest values of input value from the sin table */
00064   a = sinTable_q15[index];
00065   b = sinTable_q15[index+1];
00066 
00067   /* Linear interpolation process */
00068   sinVal = (q31_t)(0x8000-fract)*a >> 16;
00069   sinVal = (q15_t)((((q31_t)sinVal << 16) + ((q31_t)fract*b)) >> 16);
00070 
00071   return sinVal << 1;
00072 }
00073 
00074 /**
00075  * @} end of sin group
00076  */
00077