Diff: FastMathFunctions/arm_cos_q15.c

Revision:

0:3d9c67d97d6f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/FastMathFunctions/arm_cos_q15.c	Mon Jul 28 15:03:15 2014 +0000
@@ -0,0 +1,96 @@
+/* ----------------------------------------------------------------------    
+* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
+*    
+* $Date:        12. March 2014
+* $Revision: 	V1.4.3
+*    
+* Project: 	    CMSIS DSP Library    
+* Title:		arm_cos_q15.c    
+*    
+* Description:	Fast cosine calculation for Q15 values.   
+*    
+* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
+*  
+* Redistribution and use in source and binary forms, with or without 
+* modification, are permitted provided that the following conditions
+* are met:
+*   - Redistributions of source code must retain the above copyright
+*     notice, this list of conditions and the following disclaimer.
+*   - Redistributions in binary form must reproduce the above copyright
+*     notice, this list of conditions and the following disclaimer in
+*     the documentation and/or other materials provided with the 
+*     distribution.
+*   - Neither the name of ARM LIMITED nor the names of its contributors
+*     may be used to endorse or promote products derived from this
+*     software without specific prior written permission.
+*
+* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
+* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+* POSSIBILITY OF SUCH DAMAGE.   
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+#include "arm_common_tables.h"
+
+/**    
+ * @ingroup groupFastMath    
+ */
+
+ /**    
+ * @addtogroup cos    
+ * @{    
+ */
+
+/**   
+ * @brief Fast approximation to the trigonometric cosine function for Q15 data.   
+ * @param[in] x Scaled input value in radians.   
+ * @return  cos(x).   
+ *   
+ * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian
+ * value in the range [0 2*pi).
+ */
+
+q15_t arm_cos_q15(
+  q15_t x)
+{
+  q15_t sinVal;                                  /* Temporary variables for input, output */
+  int32_t index;                                 /* Index variables */
+  q15_t a, b;                                    /* Four nearest output values */
+  q15_t fract;                                   /* Temporary values for fractional values */
+
+  /* add 0.25 (pi/2) to read sine table */
+  x += 0x2000;
+  if(x < 0)
+  {   /* convert negative numbers to corresponding positive ones */
+      x = x + 0x8000;
+  }
+
+  /* Calculate the nearest index */
+  index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
+
+  /* Calculation of fractional value */
+  fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
+
+  /* Read two nearest values of input value from the sin table */
+  a = sinTable_q15[index];
+  b = sinTable_q15[index+1];
+
+  /* Linear interpolation process */
+  sinVal = (q31_t)(0x8000-fract)*a >> 16;
+  sinVal = (q15_t)((((q31_t)sinVal << 16) + ((q31_t)fract*b)) >> 16);
+
+  return sinVal << 1;
+}
+
+/**    
+ * @} end of cos group    
+ */