/* ---------------------------------------------------------------------- * Project: CMSIS DSP Library * Title: arm_atan2_q15.c * Description: q15 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]={ 0, // 0x0000 32767, // 0x7fff -1, // 0xffff -10905, // 0xd567 -144, // 0xff70 7085, // 0x1bad -680, // 0xfd58 -5719, // 0xe9a9 4393, // 0x1129 -1061 // 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> 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) { /* Negate y */ #if defined (ARM_MATH_DSP) y = __QSUB16(0, y); #else y = (y == (q15_t) 0x8000) ? (q15_t) 0x7fff : -y; #endif sign=1-sign; } if (x < 0) { sign=1 - sign; /* Negate x */ #if defined (ARM_MATH_DSP) x = __QSUB16(0, x); #else x = (x == (q15_t) 0x8000) ? (q15_t) 0x7fff : -x; #endif } if (y > x) { q15_t ratio; int16_t shift; arm_divide_q15(x,y,&ratio,&shift); /* Shift ratio by shift */ if (shift >=0) { ratio = __SSAT(((q31_t) ratio << shift), 16); } else { ratio = (ratio >> -shift); } res = PIHALFQ13 - arm_atan_limited_q15(ratio); } else { q15_t ratio; int16_t shift; arm_divide_q15(y,x,&ratio,&shift); /* Shift ratio by shift */ if (shift >=0) { ratio = __SSAT(((q31_t) ratio << shift), 16); } else { ratio = (ratio >> -shift); } res = arm_atan_limited_q15(ratio); } if (sign) { /* Negate res */ #if defined (ARM_MATH_DSP) res = __QSUB16(0, res); #else res = (res == (q15_t) 0x8000) ? (q15_t) 0x7fff : -res; #endif } 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. Returned value is between -Pi and Pi. */ ARM_DSP_ATTRIBUTE 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 { *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 */