/* ----------------------------------------------------------------------
|
* 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_q31.c
|
*
|
* Description: Fast cosine 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
|
* 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 Q31 data.
|
* @param[in] x Scaled input value in radians.
|
* @return cos(x).
|
*
|
* The Q31 input value is in the range [0 +0.9999] and is mapped to a radian
|
* value in the range [0 2*pi).
|
*/
|
|
q31_t arm_cos_q31(
|
q31_t x)
|
{
|
q31_t cosVal; /* Temporary variables for input, output */
|
int32_t index; /* Index variables */
|
q31_t a, b; /* Four nearest output values */
|
q31_t fract; /* Temporary values for fractional values */
|
|
/* add 0.25 (pi/2) to read sine table */
|
x = (uint32_t)x + 0x20000000;
|
if(x < 0)
|
{ /* convert negative numbers to corresponding positive ones */
|
x = (uint32_t)x + 0x80000000;
|
}
|
|
/* Calculate the nearest index */
|
index = (uint32_t)x >> FAST_MATH_Q31_SHIFT;
|
|
/* Calculation of fractional value */
|
fract = (x - (index << FAST_MATH_Q31_SHIFT)) << 9;
|
|
/* Read two nearest values of input value from the sin table */
|
a = sinTable_q31[index];
|
b = sinTable_q31[index+1];
|
|
/* Linear interpolation process */
|
cosVal = (q63_t)(0x80000000-fract)*a >> 32;
|
cosVal = (q31_t)((((q63_t)cosVal << 32) + ((q63_t)fract*b)) >> 32);
|
|
return cosVal << 1;
|
}
|
|
/**
|
* @} end of cos group
|
*/
|
