| /* ---------------------------------------------------------------------- | |
| * Project: CMSIS DSP Library | |
| * Title: arm_sin_q31.c | |
| * Description: Fast sine calculation for Q31 values | |
| * | |
| * $Date: 23 April 2021 | |
| * $Revision: V1.9.0 | |
| * | |
| * Target Processor: Cortex-M and Cortex-A cores | |
| * -------------------------------------------------------------------- */ | |
| /* | |
| * Copyright (C) 2010-2021 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. | |
| */ | |
| /** | |
| @ingroup groupFastMath | |
| */ | |
| /** | |
| @addtogroup sin | |
| @{ | |
| */ | |
| /** | |
| @brief Fast approximation to the trigonometric sine function for Q31 data. | |
| @param[in] x Scaled input value in radians | |
| @return sin(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_sin_q31( | |
| q31_t x) | |
| { | |
| q31_t sinVal; /* Temporary variables for input, output */ | |
| int32_t index; /* Index variable */ | |
| q31_t a, b; /* Two nearest output values */ | |
| q31_t fract; /* Temporary values for fractional values */ | |
| 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 */ | |
| sinVal = (q63_t) (0x80000000 - fract) * a >> 32; | |
| sinVal = (q31_t) ((((q63_t) sinVal << 32) + ((q63_t) fract * b)) >> 32); | |
| /* Return output value */ | |
| return (sinVal << 1); | |
| } | |
| /** | |
| @} end of sin group | |
| */ | |