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comparison f103c8/Drivers/CMSIS/DSP_Lib/Source/FastMathFunctions/arm_cos_q15.c @ 2:0c59e7a7782a

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Working on GPIO and RCC
author cin
date Mon, 16 Jan 2017 11:04:47 +0300
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1:a0b14b11ad9f 2:0c59e7a7782a
1 /* ----------------------------------------------------------------------
2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
3 *
4 * $Date: 07. September 2015
5 * $Revision: V.1.4.5 a
6 *
7 * Project: CMSIS DSP Library
8 * Title: arm_cos_q15.c
9 *
10 * Description: Fast cosine calculation for Q15 values.
11 *
12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * - Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * - Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in
21 * the documentation and/or other materials provided with the
22 * distribution.
23 * - Neither the name of ARM LIMITED nor the names of its contributors
24 * may be used to endorse or promote products derived from this
25 * software without specific prior written permission.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
38 * POSSIBILITY OF SUCH DAMAGE.
39 * -------------------------------------------------------------------- */
40
41 #include "arm_math.h"
42 #include "arm_common_tables.h"
43
44 /**
45 * @ingroup groupFastMath
46 */
47
48 /**
49 * @addtogroup cos
50 * @{
51 */
52
53 /**
54 * @brief Fast approximation to the trigonometric cosine function for Q15 data.
55 * @param[in] x Scaled input value in radians.
56 * @return cos(x).
57 *
58 * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian
59 * value in the range [0 2*pi).
60 */
61
62 q15_t arm_cos_q15(
63 q15_t x)
64 {
65 q15_t cosVal; /* Temporary variables for input, output */
66 int32_t index; /* Index variables */
67 q15_t a, b; /* Four nearest output values */
68 q15_t fract; /* Temporary values for fractional values */
69
70 /* add 0.25 (pi/2) to read sine table */
71 x = (uint16_t)x + 0x2000;
72 if(x < 0)
73 { /* convert negative numbers to corresponding positive ones */
74 x = (uint16_t)x + 0x8000;
75 }
76
77 /* Calculate the nearest index */
78 index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
79
80 /* Calculation of fractional value */
81 fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
82
83 /* Read two nearest values of input value from the sin table */
84 a = sinTable_q15[index];
85 b = sinTable_q15[index+1];
86
87 /* Linear interpolation process */
88 cosVal = (q31_t)(0x8000-fract)*a >> 16;
89 cosVal = (q15_t)((((q31_t)cosVal << 16) + ((q31_t)fract*b)) >> 16);
90
91 return cosVal << 1;
92 }
93
94 /**
95 * @} end of cos group
96 */