arm_sin_cos_q31.c

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/* ----------------------------------------------------------------------    
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
*    
* $Date:        19. March 2015
* $Revision:    V.1.4.5
*    
* Project:      CMSIS DSP Library    
* Title:        arm_sin_cos_q31.c    
*    
* Description:  Cosine & Sine calculation for Q31 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
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*     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
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* -------------------------------------------------------------------- */

#include "arm_math.h"
#include "arm_common_tables.h"

void arm_sin_cos_q31(
  q31_t theta,
  q31_t * pSinVal,
  q31_t * pCosVal)
{
  q31_t fract;                                 /* Temporary variables for input, output */
  uint16_t indexS, indexC;                     /* Index variable */
  q31_t f1, f2, d1, d2;                        /* Two nearest output values */
  q31_t Dn, Df;
  q63_t temp;
  
  /* Calculate the nearest index */
  indexS = (uint32_t)theta >> CONTROLLER_Q31_SHIFT;
  indexC = (indexS + 128) & 0x1ff;

  /* Calculation of fractional value */
  fract = (theta - (indexS << CONTROLLER_Q31_SHIFT)) << 8;
  
  /* Read two nearest values of input value from the cos & sin tables */
  f1 = sinTable_q31[indexC+0];
  f2 = sinTable_q31[indexC+1];
  d1 = -sinTable_q31[indexS+0];
  d2 = -sinTable_q31[indexS+1];

  Dn = 0x1921FB5; // delta between the two points (fixed), in this case 2*pi/FAST_MATH_TABLE_SIZE
  Df = f2 - f1; // delta between the values of the functions
  temp = Dn*((q63_t)d1 + d2);
  temp = temp - ((q63_t)Df << 32);
  temp = (q63_t)fract*(temp >> 31);
  temp = temp + ((3*(q63_t)Df << 31) - (d2 + ((q63_t)d1 << 1))*Dn);
  temp = (q63_t)fract*(temp >> 31);
  temp = temp + (q63_t)d1*Dn;
  temp = (q63_t)fract*(temp >> 31);

  /* Calculation of cosine value */
  *pCosVal = clip_q63_to_q31((temp >> 31) + (q63_t)f1);
  
  /* Read two nearest values of input value from the cos & sin tables */
  f1 = sinTable_q31[indexS+0];
  f2 = sinTable_q31[indexS+1];
  d1 = sinTable_q31[indexC+0];
  d2 = sinTable_q31[indexC+1];

  Df = f2 - f1; // delta between the values of the functions
  temp = Dn*((q63_t)d1 + d2);
  temp = temp - ((q63_t)Df << 32);
  temp = (q63_t)fract*(temp >> 31);
  temp = temp + ((3*(q63_t)Df << 31) - (d2 + ((q63_t)d1 << 1))*Dn);
  temp = (q63_t)fract*(temp >> 31);
  temp = temp + (q63_t)d1*Dn;
  temp = (q63_t)fract*(temp >> 31);
  
  /* Calculation of sine value */
  *pSinVal = clip_q63_to_q31((temp >> 31) + (q63_t)f1);
}