arm_sin_q15.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        19. March 2015
00005 * $Revision:    V.1.4.5
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_sin_q15.c    
00009 *    
00010 * Description:  Fast sine calculation for Q15 values.   
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE. 
00039 * -------------------------------------------------------------------- */
00040 
00041 #include "arm_math.h"
00042 #include "arm_common_tables.h"
00043 
00044 /**    
00045  * @ingroup groupFastMath    
00046  */
00047 
00048  /**    
00049  * @addtogroup sin    
00050  * @{    
00051  */
00052 
00053 /**   
00054  * @brief Fast approximation to the trigonometric sine function for Q15 data.   
00055  * @param[in] x Scaled input value in radians.   
00056  * @return  sin(x).   
00057  *   
00058  * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian value in the range [0 2*pi).
00059  */
00060 
00061 q15_t arm_sin_q15(
00062   q15_t x)
00063 {
00064   q15_t sinVal;                                  /* Temporary variables for input, output */
00065   int32_t index;                                 /* Index variables */
00066   q15_t a, b;                                    /* Four nearest output values */
00067   q15_t fract;                                   /* Temporary values for fractional values */
00068 
00069   /* Calculate the nearest index */
00070   index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
00071 
00072   /* Calculation of fractional value */
00073   fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
00074 
00075   /* Read two nearest values of input value from the sin table */
00076   a = sinTable_q15[index];
00077   b = sinTable_q15[index+1];
00078 
00079   /* Linear interpolation process */
00080   sinVal = (q31_t)(0x8000-fract)*a >> 16;
00081   sinVal = (q15_t)((((q31_t)sinVal << 16) + ((q31_t)fract*b)) >> 16);
00082 
00083   return sinVal << 1;
00084 }
00085 
00086 /**    
00087  * @} end of sin group    
00088  */