|
2
|
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 */
|
