arm_sin_f32.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        12. March 2014
00005 * $Revision:    V1.4.3
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_sin_f32.c    
00009 *    
00010 * Description:  Fast sine calculation for floating-point 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  * @defgroup sin Sine    
00050  *    
00051  * Computes the trigonometric sine function using a combination of table lookup   
00052  * and cubic interpolation.  There are separate functions for   
00053  * Q15, Q31, and floating-point data types.   
00054  * The input to the floating-point version is in radians while the   
00055  * fixed-point Q15 and Q31 have a scaled input with the range   
00056  * [0 +0.9999] mapping to [0 2*pi).  The fixed-point range is chosen so that a
00057  * value of 2*pi wraps around to 0.
00058  *   
00059  * The implementation is based on table lookup using 256 values together with cubic interpolation.   
00060  * The steps used are:   
00061  *  -# Calculation of the nearest integer table index   
00062  *  -# Fetch the four table values a, b, c, and d     
00063  *  -# Compute the fractional portion (fract) of the table index.   
00064  *  -# Calculation of wa, wb, wc, wd    
00065  *  -# The final result equals <code>a*wa + b*wb + c*wc + d*wd</code>   
00066  *   
00067  * where   
00068  * <pre>    
00069  *    a=Table[index-1];    
00070  *    b=Table[index+0];    
00071  *    c=Table[index+1];    
00072  *    d=Table[index+2];    
00073  * </pre>   
00074  * and   
00075  * <pre>    
00076  *    wa=-(1/6)*fract.^3 + (1/2)*fract.^2 - (1/3)*fract;    
00077  *    wb=(1/2)*fract.^3 - fract.^2 - (1/2)*fract + 1;    
00078  *    wc=-(1/2)*fract.^3+(1/2)*fract.^2+fract;    
00079  *    wd=(1/6)*fract.^3 - (1/6)*fract;    
00080  * </pre>    
00081  */
00082 
00083 /**    
00084  * @addtogroup sin    
00085  * @{    
00086  */
00087 
00088 /**   
00089  * @brief  Fast approximation to the trigonometric sine function for floating-point data.   
00090  * @param[in] x input value in radians.   
00091  * @return  sin(x).   
00092  */
00093 
00094 float32_t arm_sin_f32(
00095   float32_t x)
00096 {
00097   float32_t sinVal, fract, in;                           /* Temporary variables for input, output */
00098   uint16_t index;                                        /* Index variable */
00099   float32_t a, b;                                        /* Two nearest output values */
00100   int32_t n;
00101   float32_t findex;
00102 
00103   /* input x is in radians */
00104   /* Scale the input to [0 1] range from [0 2*PI] , divide input by 2*pi */
00105   in = x * 0.159154943092f;
00106 
00107   /* Calculation of floor value of input */
00108   n = (int32_t) in;
00109 
00110   /* Make negative values towards -infinity */
00111   if(x < 0.0f)
00112   {
00113     n--;
00114   }
00115 
00116   /* Map input value to [0 1] */
00117   in = in - (float32_t) n;
00118 
00119   /* Calculation of index of the table */
00120   findex = (float32_t) FAST_MATH_TABLE_SIZE * in;
00121   index = ((uint16_t)findex) & 0x1ff;
00122 
00123   /* fractional value calculation */
00124   fract = findex - (float32_t) index;
00125 
00126   /* Read two nearest values of input value from the sin table */
00127   a = sinTable_f32[index];
00128   b = sinTable_f32[index+1];
00129 
00130   /* Linear interpolation process */
00131   sinVal = (1.0f-fract)*a + fract*b;
00132 
00133   /* Return the output value */
00134   return (sinVal);
00135 }
00136 
00137 /**    
00138  * @} end of sin group    
00139  */