Diff: cmsis_dsp/FastMathFunctions/arm_cos_q15.c

Revision:

5:3762170b6d4d

Parent:

3:7a284390b0ce

--- a/cmsis_dsp/FastMathFunctions/arm_cos_q15.c	Mon Jun 23 09:30:09 2014 +0100
+++ b/cmsis_dsp/FastMathFunctions/arm_cos_q15.c	Fri Nov 20 08:45:18 2015 +0000
@@ -1,24 +1,24 @@
-/* ----------------------------------------------------------------------    
-* Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
-*    
-* $Date:        17. January 2013
-* $Revision: 	V1.4.1
-*    
-* Project: 	    CMSIS DSP Library    
-* Title:		arm_cos_q15.c    
-*    
-* Description:	Fast cosine calculation for Q15 values.   
-*    
+/* ----------------------------------------------------------------------
+* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
+*
+* $Date:        07. September 2015
+* $Revision:    V.1.4.5 a
+*
+* 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 
+*
+* 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 
+*     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
@@ -27,7 +27,7 @@
 * 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 
+* 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;
@@ -35,81 +35,26 @@
 * 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.   
+* POSSIBILITY OF SUCH DAMAGE.
 * -------------------------------------------------------------------- */
 
 #include "arm_math.h"
+#include "arm_common_tables.h"
 
-/**    
- * @ingroup groupFastMath    
- */
-
- /**    
- * @addtogroup cos    
- * @{    
+/**
+ * @ingroup groupFastMath
  */
 
-/**   
-* \par    
- * Table values are in Q15 (1.15 fixed-point format) and generation is done in 
- * three steps.  First,  generate cos values in floating point:    
- * <pre>
- * tableSize = 256;
- * for(n = -1; n < (tableSize + 1); n++)    
- * {    
- *	cosTable[n+1]= cos(2*pi*n/tableSize);    
- * } </pre>     
- * where pi value is  3.14159265358979    
- * \par    
- * Second, convert floating-point to Q15 (fixed-point):    
- *	(cosTable[i] * pow(2, 15))    
- * \par    
- * Finally, round to the nearest integer value:
- * 	cosTable[i] += (cosTable[i] > 0 ? 0.5 :-0.5);    
-*/
+ /**
+ * @addtogroup cos
+ * @{
+ */
 
-static const q15_t cosTableQ15[259] = {
-  0x7ff6, 0x7fff, 0x7ff6, 0x7fd9, 0x7fa7, 0x7f62, 0x7f0a, 0x7e9d,
-  0x7e1e, 0x7d8a, 0x7ce4, 0x7c2a, 0x7b5d, 0x7a7d, 0x798a, 0x7885,
-  0x776c, 0x7642, 0x7505, 0x73b6, 0x7255, 0x70e3, 0x6f5f, 0x6dca,
-  0x6c24, 0x6a6e, 0x68a7, 0x66d0, 0x64e9, 0x62f2, 0x60ec, 0x5ed7,
-  0x5cb4, 0x5a82, 0x5843, 0x55f6, 0x539b, 0x5134, 0x4ec0, 0x4c40,
-  0x49b4, 0x471d, 0x447b, 0x41ce, 0x3f17, 0x3c57, 0x398d, 0x36ba,
-  0x33df, 0x30fc, 0x2e11, 0x2b1f, 0x2827, 0x2528, 0x2224, 0x1f1a,
-  0x1c0c, 0x18f9, 0x15e2, 0x12c8, 0xfab, 0xc8c, 0x96b, 0x648,
-  0x324, 0x0, 0xfcdc, 0xf9b8, 0xf695, 0xf374, 0xf055, 0xed38,
-  0xea1e, 0xe707, 0xe3f4, 0xe0e6, 0xdddc, 0xdad8, 0xd7d9, 0xd4e1,
-  0xd1ef, 0xcf04, 0xcc21, 0xc946, 0xc673, 0xc3a9, 0xc0e9, 0xbe32,
-  0xbb85, 0xb8e3, 0xb64c, 0xb3c0, 0xb140, 0xaecc, 0xac65, 0xaa0a,
-  0xa7bd, 0xa57e, 0xa34c, 0xa129, 0x9f14, 0x9d0e, 0x9b17, 0x9930,
-  0x9759, 0x9592, 0x93dc, 0x9236, 0x90a1, 0x8f1d, 0x8dab, 0x8c4a,
-  0x8afb, 0x89be, 0x8894, 0x877b, 0x8676, 0x8583, 0x84a3, 0x83d6,
-  0x831c, 0x8276, 0x81e2, 0x8163, 0x80f6, 0x809e, 0x8059, 0x8027,
-  0x800a, 0x8000, 0x800a, 0x8027, 0x8059, 0x809e, 0x80f6, 0x8163,
-  0x81e2, 0x8276, 0x831c, 0x83d6, 0x84a3, 0x8583, 0x8676, 0x877b,
-  0x8894, 0x89be, 0x8afb, 0x8c4a, 0x8dab, 0x8f1d, 0x90a1, 0x9236,
-  0x93dc, 0x9592, 0x9759, 0x9930, 0x9b17, 0x9d0e, 0x9f14, 0xa129,
-  0xa34c, 0xa57e, 0xa7bd, 0xaa0a, 0xac65, 0xaecc, 0xb140, 0xb3c0,
-  0xb64c, 0xb8e3, 0xbb85, 0xbe32, 0xc0e9, 0xc3a9, 0xc673, 0xc946,
-  0xcc21, 0xcf04, 0xd1ef, 0xd4e1, 0xd7d9, 0xdad8, 0xdddc, 0xe0e6,
-  0xe3f4, 0xe707, 0xea1e, 0xed38, 0xf055, 0xf374, 0xf695, 0xf9b8,
-  0xfcdc, 0x0, 0x324, 0x648, 0x96b, 0xc8c, 0xfab, 0x12c8,
-  0x15e2, 0x18f9, 0x1c0c, 0x1f1a, 0x2224, 0x2528, 0x2827, 0x2b1f,
-  0x2e11, 0x30fc, 0x33df, 0x36ba, 0x398d, 0x3c57, 0x3f17, 0x41ce,
-  0x447b, 0x471d, 0x49b4, 0x4c40, 0x4ec0, 0x5134, 0x539b, 0x55f6,
-  0x5843, 0x5a82, 0x5cb4, 0x5ed7, 0x60ec, 0x62f2, 0x64e9, 0x66d0,
-  0x68a7, 0x6a6e, 0x6c24, 0x6dca, 0x6f5f, 0x70e3, 0x7255, 0x73b6,
-  0x7505, 0x7642, 0x776c, 0x7885, 0x798a, 0x7a7d, 0x7b5d, 0x7c2a,
-  0x7ce4, 0x7d8a, 0x7e1e, 0x7e9d, 0x7f0a, 0x7f62, 0x7fa7, 0x7fd9,
-  0x7ff6, 0x7fff, 0x7ff6
-};
-
-
-/**   
- * @brief Fast approximation to the trigonometric cosine function for Q15 data.   
- * @param[in] x Scaled input value in radians.   
- * @return  cos(x).   
- *   
+/**
+ * @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).
  */
@@ -117,98 +62,35 @@
 q15_t arm_cos_q15(
   q15_t x)
 {
-  q31_t cosVal;                                  /* Temporary variable for output */
-  q15_t *tablePtr;                               /* Pointer to table */
-  q15_t in, in2;                                 /* Temporary variables for input */
-  q31_t wa, wb, wc, wd;                          /* Cubic interpolation coefficients */
-  q15_t a, b, c, d;                              /* Four nearest output values */
-  q15_t fract, fractCube, fractSquare;           /* Variables for fractional value */
-  q15_t oneBy6 = 0x1555;                         /* Fixed point value of 1/6 */
-  q15_t tableSpacing = TABLE_SPACING_Q15;        /* Table spacing */
-  int32_t index;                                 /* Index variable */
-
-  in = x;
-
-  /* Calculate the nearest index */
-  index = (int32_t) in / tableSpacing;
-
-  /* Calculate the nearest value of input */
-  in2 = (q15_t) index *tableSpacing;
+  q15_t cosVal;                                  /* 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 */
 
-  /* Calculation of fractional value */
-  fract = (in - in2) << 8;
-
-  /* fractSquare = fract * fract */
-  fractSquare = (q15_t) ((fract * fract) >> 15);
-
-  /* fractCube = fract * fract * fract */
-  fractCube = (q15_t) ((fractSquare * fract) >> 15);
-
-  /* Checking min and max index of table */
-  if(index < 0)
-  {
-    index = 0;
-  }
-  else if(index > 256)
-  {
-    index = 256;
+  /* add 0.25 (pi/2) to read sine table */
+  x = (uint16_t)x + 0x2000;
+  if(x < 0)
+  {   /* convert negative numbers to corresponding positive ones */
+      x = (uint16_t)x + 0x8000;
   }
 
-  /* Initialise table pointer */
-  tablePtr = (q15_t *) & cosTableQ15[index];
-
-  /* Cubic interpolation process */
-  /* Calculation of wa */
-  /* wa = -(oneBy6)*fractCube + (fractSquare >> 1u) - (0x2AAA)*fract; */
-  wa = (q31_t) oneBy6 *fractCube;
-  wa += (q31_t) 0x2AAA *fract;
-  wa = -(wa >> 15);
-  wa += (fractSquare >> 1u);
+  /* Calculate the nearest index */
+  index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
 
-  /* Read first nearest value of output from the cos table */
-  a = *tablePtr++;
-
-  /* cosVal = a * wa */
-  cosVal = a * wa;
-
-  /* Calculation of wb */
-  wb = (((fractCube >> 1u) - fractSquare) - (fract >> 1u)) + 0x7FFF;
-
-  /* Read second nearest value of output from the cos table */
-  b = *tablePtr++;
-
-  /*      cosVal += b*wb */
-  cosVal += b * wb;
+  /* Calculation of fractional value */
+  fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
 
-  /* Calculation of wc */
-  wc = -(q31_t) fractCube + fractSquare;
-  wc = (wc >> 1u) + fract;
-
-  /* Read third nearest value of output from the cos table */
-  c = *tablePtr++;
-
-  /* cosVal += c*wc */
-  cosVal += c * wc;
+  /* Read two nearest values of input value from the sin table */
+  a = sinTable_q15[index];
+  b = sinTable_q15[index+1];
 
-  /* Calculation of wd */
-  /* wd = (oneBy6)*fractCube - (oneBy6)*fract; */
-  fractCube = fractCube - fract;
-  wd = ((q15_t) (((q31_t) oneBy6 * fractCube) >> 15));
-
-  /* Read fourth nearest value of output from the cos table */
-  d = *tablePtr++;
+  /* Linear interpolation process */
+  cosVal = (q31_t)(0x8000-fract)*a >> 16;
+  cosVal = (q15_t)((((q31_t)cosVal << 16) + ((q31_t)fract*b)) >> 16);
 
-  /* cosVal += d*wd; */
-  cosVal += d * wd;
-
-  /* Convert output value in 1.15(q15) format and saturate */
-  cosVal = __SSAT((cosVal >> 15), 16);
-
-  /* Return the output value in 1.15(q15) format */
-  return ((q15_t) cosVal);
-
+  return cosVal << 1;
 }
 
-/**    
- * @} end of cos group    
+/**
+ * @} end of cos group
  */