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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_atan2_q15.c
* Description: float32 Arc tangent of y/x
*
* $Date: 22 April 2022
* $Revision: V1.10.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2022 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "dsp/fast_math_functions.h"
#include "dsp/utils.h"
/*
atan for argument between in [0, 1.0]
*/
/* Q2.13 */
#define ATANHALFQ13 0xed6
#define PIHALFQ13 0x3244
#define PIQ13 0x6488
#define ATAN2_NB_COEFS_Q15 10
static const q15_t atan2_coefs_q15[ATAN2_NB_COEFS_Q15]={0x0000
,0x7fff
,0xffff
,0xd567
,0xff70
,0x1bad
,0xfd58
,0xe9a9
,0x1129
,0xfbdb
};
__STATIC_FORCEINLINE q15_t arm_atan_limited_q15(q15_t x)
{
q31_t res=(q31_t)atan2_coefs_q15[ATAN2_NB_COEFS_Q15-1];
int i=1;
for(i=1;i<ATAN2_NB_COEFS_Q15;i++)
{
res = ((q31_t) x * res) >> 15U;
res = res + ((q31_t) atan2_coefs_q15[ATAN2_NB_COEFS_Q15-1-i]) ;
}
res = __SSAT(res>>2,16);
return(res);
}
__STATIC_FORCEINLINE q15_t arm_atan_q15(q15_t y,q15_t x)
{
int sign=0;
q15_t res=0;
if (y<0)
{
arm_negate_q15(&y,&y,1);
sign=1-sign;
}
if (x < 0)
{
sign=1 - sign;
arm_negate_q15(&x,&x,1);
}
if (y > x)
{
q15_t ratio;
int16_t shift;
arm_divide_q15(x,y,&ratio,&shift);
arm_shift_q15(&ratio,shift,&ratio,1);
res = PIHALFQ13 - arm_atan_limited_q15(ratio);
}
else
{
q15_t ratio;
int16_t shift;
arm_divide_q15(y,x,&ratio,&shift);
arm_shift_q15(&ratio,shift,&ratio,1);
res = arm_atan_limited_q15(ratio);
}
if (sign)
{
arm_negate_q15(&res,&res,1);
}
return(res);
}
/**
@ingroup groupFastMath
*/
/**
@addtogroup atan2
@{
*/
/**
@brief Arc Tangent of y/x using sign of y and x to get right quadrant
@param[in] y y coordinate
@param[in] x x coordinate
@param[out] result Result in Q2.13
@return error status.
@par Compute the Arc tangent of y/x:
The sign of y and x are used to determine the right quadrant
and compute the right angle.
*/
arm_status arm_atan2_q15(q15_t y,q15_t x,q15_t *result)
{
if (x > 0)
{
*result=arm_atan_q15(y,x);
return(ARM_MATH_SUCCESS);
}
if (x < 0)
{
if (y > 0)
{
*result=arm_atan_q15(y,x) + PIQ13;
}
else if (y < 0)
{
*result=arm_atan_q15(y,x) - PIQ13;
}
else
{
if (y<0)
{
*result= -PIQ13;
}
else
{
*result= PIQ13;
}
}
return(ARM_MATH_SUCCESS);
}
if (x == 0)
{
if (y > 0)
{
*result=PIHALFQ13;
return(ARM_MATH_SUCCESS);
}
if (y < 0)
{
*result=-PIHALFQ13;
return(ARM_MATH_SUCCESS);
}
}
return(ARM_MATH_NANINF);
}
/**
@} end of atan2 group
*/
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