| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_sin_f32.c |
| * Description: Fast sine calculation for floating-point values |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 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 "arm_math.h" |
| #include "arm_common_tables.h" |
| |
| /** |
| @ingroup groupFastMath |
| */ |
| |
| /** |
| @defgroup sin Sine |
| |
| Computes the trigonometric sine function using a combination of table lookup |
| and linear interpolation. There are separate functions for |
| Q15, Q31, and floating-point data types. |
| The input to the floating-point version is in radians while the |
| fixed-point Q15 and Q31 have a scaled input with the range |
| [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a |
| value of 2*pi wraps around to 0. |
| |
| The implementation is based on table lookup using 256 values together with linear interpolation. |
| The steps used are: |
| -# Calculation of the nearest integer table index |
| -# Compute the fractional portion (fract) of the table index. |
| -# The final result equals <code>(1.0f-fract)*a + fract*b;</code> |
| |
| where |
| <pre> |
| b = Table[index]; |
| c = Table[index+1]; |
| </pre> |
| */ |
| |
| /** |
| @addtogroup sin |
| @{ |
| */ |
| |
| /** |
| @brief Fast approximation to the trigonometric sine function for floating-point data. |
| @param[in] x input value in radians. |
| @return sin(x) |
| */ |
| |
| float32_t arm_sin_f32( |
| float32_t x) |
| { |
| float32_t sinVal, fract, in; /* Temporary input, output variables */ |
| uint16_t index; /* Index variable */ |
| float32_t a, b; /* Two nearest output values */ |
| int32_t n; |
| float32_t findex; |
| |
| /* input x is in radians */ |
| /* Scale input to [0 1] range from [0 2*PI] , divide input by 2*pi */ |
| in = x * 0.159154943092f; |
| |
| /* Calculation of floor value of input */ |
| n = (int32_t) in; |
| |
| /* Make negative values towards -infinity */ |
| if (in < 0.0f) |
| { |
| n--; |
| } |
| |
| /* Map input value to [0 1] */ |
| in = in - (float32_t) n; |
| |
| /* Calculation of index of the table */ |
| findex = (float32_t)FAST_MATH_TABLE_SIZE * in; |
| index = (uint16_t)findex; |
| |
| /* when "in" is exactly 1, we need to rotate the index down to 0 */ |
| if (index >= FAST_MATH_TABLE_SIZE) { |
| index = 0; |
| findex -= (float32_t)FAST_MATH_TABLE_SIZE; |
| } |
| |
| /* fractional value calculation */ |
| fract = findex - (float32_t) index; |
| |
| /* Read two nearest values of input value from the sin table */ |
| a = sinTable_f32[index]; |
| b = sinTable_f32[index+1]; |
| |
| /* Linear interpolation process */ |
| sinVal = (1.0f - fract) * a + fract * b; |
| |
| /* Return output value */ |
| return (sinVal); |
| } |
| |
| /** |
| @} end of sin group |
| */ |