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| 56 | mjames | 1 | /* ---------------------------------------------------------------------- |
| 2 | * Project: CMSIS DSP Library |
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| 3 | * Title: arm_sin_f32.c |
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| 4 | * Description: Fast sine calculation for floating-point values |
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| 5 | * |
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| 6 | * $Date: 27. January 2017 |
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| 7 | * $Revision: V.1.5.1 |
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| 8 | * |
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| 9 | * Target Processor: Cortex-M cores |
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| 10 | * -------------------------------------------------------------------- */ |
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| 11 | /* |
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| 12 | * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. |
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| 13 | * |
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| 14 | * SPDX-License-Identifier: Apache-2.0 |
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| 15 | * |
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| 16 | * Licensed under the Apache License, Version 2.0 (the License); you may |
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| 17 | * not use this file except in compliance with the License. |
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| 18 | * You may obtain a copy of the License at |
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| 19 | * |
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| 20 | * www.apache.org/licenses/LICENSE-2.0 |
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| 21 | * |
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| 22 | * Unless required by applicable law or agreed to in writing, software |
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| 23 | * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
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| 24 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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| 25 | * See the License for the specific language governing permissions and |
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| 26 | * limitations under the License. |
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| 27 | */ |
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| 28 | |||
| 29 | #include "arm_math.h" |
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| 30 | #include "arm_common_tables.h" |
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| 31 | #include <math.h> |
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| 32 | |||
| 33 | /** |
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| 34 | * @ingroup groupFastMath |
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| 35 | */ |
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| 36 | |||
| 37 | /** |
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| 38 | * @defgroup sin Sine |
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| 39 | * |
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| 40 | * Computes the trigonometric sine function using a combination of table lookup |
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| 41 | * and linear interpolation. There are separate functions for |
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| 42 | * Q15, Q31, and floating-point data types. |
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| 43 | * The input to the floating-point version is in radians and in the range [0 2*pi) while the |
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| 44 | * fixed-point Q15 and Q31 have a scaled input with the range |
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| 45 | * [0 +0.9999] mapping to [0 2*pi). The fixed-point range is chosen so that a |
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| 46 | * value of 2*pi wraps around to 0. |
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| 47 | * |
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| 48 | * The implementation is based on table lookup using 256 values together with linear interpolation. |
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| 49 | * The steps used are: |
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| 50 | * -# Calculation of the nearest integer table index |
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| 51 | * -# Compute the fractional portion (fract) of the table index. |
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| 52 | * -# The final result equals <code>(1.0f-fract)*a + fract*b;</code> |
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| 53 | * |
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| 54 | * where |
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| 55 | * <pre> |
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| 56 | * b=Table[index+0]; |
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| 57 | * c=Table[index+1]; |
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| 58 | * </pre> |
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| 59 | */ |
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| 60 | |||
| 61 | /** |
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| 62 | * @addtogroup sin |
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| 63 | * @{ |
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| 64 | */ |
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| 65 | |||
| 66 | /** |
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| 67 | * @brief Fast approximation to the trigonometric sine function for floating-point data. |
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| 68 | * @param[in] x input value in radians. |
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| 69 | * @return sin(x). |
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| 70 | */ |
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| 71 | |||
| 72 | float32_t arm_sin_f32( |
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| 73 | float32_t x) |
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| 74 | { |
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| 75 | float32_t sinVal, fract, in; /* Temporary variables for input, output */ |
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| 76 | uint16_t index; /* Index variable */ |
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| 77 | float32_t a, b; /* Two nearest output values */ |
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| 78 | int32_t n; |
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| 79 | float32_t findex; |
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| 80 | |||
| 81 | /* Special case for small negative inputs */ |
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| 82 | if ((x < 0.0f) && (x >= -1.9e-7f)) { |
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| 83 | return x; |
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| 84 | } |
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| 85 | |||
| 86 | /* input x is in radians */ |
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| 87 | /* Scale the input to [0 1] range from [0 2*PI] , divide input by 2*pi */ |
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| 88 | in = x * 0.159154943092f; |
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| 89 | |||
| 90 | /* Calculation of floor value of input */ |
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| 91 | n = (int32_t) in; |
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| 92 | |||
| 93 | /* Make negative values towards -infinity */ |
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| 94 | if (x < 0.0f) |
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| 95 | { |
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| 96 | n--; |
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| 97 | } |
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| 98 | |||
| 99 | /* Map input value to [0 1] */ |
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| 100 | in = in - (float32_t) n; |
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| 101 | |||
| 102 | /* Calculation of index of the table */ |
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| 103 | findex = (float32_t) FAST_MATH_TABLE_SIZE * in; |
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| 104 | |||
| 105 | index = ((uint16_t)findex) & 0x1ff; |
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| 106 | |||
| 107 | /* fractional value calculation */ |
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| 108 | fract = findex - (float32_t) index; |
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| 109 | |||
| 110 | /* Read two nearest values of input value from the sin table */ |
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| 111 | a = sinTable_f32[index]; |
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| 112 | b = sinTable_f32[index+1]; |
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| 113 | |||
| 114 | /* Linear interpolation process */ |
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| 115 | sinVal = (1.0f-fract)*a + fract*b; |
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| 116 | |||
| 117 | /* Return the output value */ |
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| 118 | return (sinVal); |
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| 119 | } |
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| 120 | |||
| 121 | /** |
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| 122 | * @} end of sin group |
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| 123 | */ |