mbed official / mbed-dsp

CMSIS DSP library

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cmsis_dsp/FastMathFunctions/arm_cos_q15.c@5:3762170b6d4d, 2015-11-20 (annotated)

Committer:
mbed_official
Date:
Fri Nov 20 08:45:18 2015 +0000
Revision:
5:3762170b6d4d
Parent:
3:7a284390b0ce 
Synchronized with git revision 2eb940b9a73af188d3004a2575fdfbb05febe62b



Full URL: https://github.com/mbedmicro/mbed/commit/2eb940b9a73af188d3004a2575fdfbb05febe62b/



Added option to build rpc library. closes #1426

Who changed what in which revision?

UserRevisionLine numberNew contents of line
mbed_official 5:3762170b6d4d 1 /* ----------------------------------------------------------------------
mbed_official 5:3762170b6d4d 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
mbed_official 5:3762170b6d4d 3 *
mbed_official 5:3762170b6d4d 4 * $Date: 07. September 2015
mbed_official 5:3762170b6d4d 5 * $Revision: V.1.4.5 a
mbed_official 5:3762170b6d4d 6 *
mbed_official 5:3762170b6d4d 7 * Project: CMSIS DSP Library
mbed_official 5:3762170b6d4d 8 * Title: arm_cos_q15.c
mbed_official 5:3762170b6d4d 9 *
mbed_official 5:3762170b6d4d 10 * Description: Fast cosine calculation for Q15 values.
mbed_official 5:3762170b6d4d 11 *
emilmont 1:fdd22bb7aa52 12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
mbed_official 5:3762170b6d4d 13 *
mbed_official 5:3762170b6d4d 14 * Redistribution and use in source and binary forms, with or without
mbed_official 3:7a284390b0ce 15 * modification, are permitted provided that the following conditions
mbed_official 3:7a284390b0ce 16 * are met:
mbed_official 3:7a284390b0ce 17 * - Redistributions of source code must retain the above copyright
mbed_official 3:7a284390b0ce 18 * notice, this list of conditions and the following disclaimer.
mbed_official 3:7a284390b0ce 19 * - Redistributions in binary form must reproduce the above copyright
mbed_official 3:7a284390b0ce 20 * notice, this list of conditions and the following disclaimer in
mbed_official 5:3762170b6d4d 21 * the documentation and/or other materials provided with the
mbed_official 3:7a284390b0ce 22 * distribution.
mbed_official 3:7a284390b0ce 23 * - Neither the name of ARM LIMITED nor the names of its contributors
mbed_official 3:7a284390b0ce 24 * may be used to endorse or promote products derived from this
mbed_official 3:7a284390b0ce 25 * software without specific prior written permission.
mbed_official 3:7a284390b0ce 26 *
mbed_official 3:7a284390b0ce 27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
mbed_official 3:7a284390b0ce 28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
mbed_official 3:7a284390b0ce 29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
mbed_official 5:3762170b6d4d 30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
mbed_official 3:7a284390b0ce 31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
mbed_official 3:7a284390b0ce 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
mbed_official 3:7a284390b0ce 33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
mbed_official 3:7a284390b0ce 34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
mbed_official 3:7a284390b0ce 35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
mbed_official 3:7a284390b0ce 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
mbed_official 3:7a284390b0ce 37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
mbed_official 5:3762170b6d4d 38 * POSSIBILITY OF SUCH DAMAGE.
emilmont 1:fdd22bb7aa52 39 * -------------------------------------------------------------------- */
emilmont 1:fdd22bb7aa52 40
emilmont 1:fdd22bb7aa52 41 #include "arm_math.h"
mbed_official 5:3762170b6d4d 42 #include "arm_common_tables.h"
emilmont 1:fdd22bb7aa52 43
mbed_official 5:3762170b6d4d 44 /**
mbed_official 5:3762170b6d4d 45 * @ingroup groupFastMath
emilmont 1:fdd22bb7aa52 46 */
emilmont 1:fdd22bb7aa52 47
mbed_official 5:3762170b6d4d 48 /**
mbed_official 5:3762170b6d4d 49 * @addtogroup cos
mbed_official 5:3762170b6d4d 50 * @{
mbed_official 5:3762170b6d4d 51 */
emilmont 1:fdd22bb7aa52 52
mbed_official 5:3762170b6d4d 53 /**
mbed_official 5:3762170b6d4d 54 * @brief Fast approximation to the trigonometric cosine function for Q15 data.
mbed_official 5:3762170b6d4d 55 * @param[in] x Scaled input value in radians.
mbed_official 5:3762170b6d4d 56 * @return cos(x).
mbed_official 5:3762170b6d4d 57 *
mbed_official 3:7a284390b0ce 58 * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian
mbed_official 3:7a284390b0ce 59 * value in the range [0 2*pi).
emilmont 1:fdd22bb7aa52 60 */
emilmont 1:fdd22bb7aa52 61
emilmont 1:fdd22bb7aa52 62 q15_t arm_cos_q15(
emilmont 1:fdd22bb7aa52 63 q15_t x)
emilmont 1:fdd22bb7aa52 64 {
mbed_official 5:3762170b6d4d 65 q15_t cosVal; /* Temporary variables for input, output */
mbed_official 5:3762170b6d4d 66 int32_t index; /* Index variables */
mbed_official 5:3762170b6d4d 67 q15_t a, b; /* Four nearest output values */
mbed_official 5:3762170b6d4d 68 q15_t fract; /* Temporary values for fractional values */
emilmont 1:fdd22bb7aa52 69
mbed_official 5:3762170b6d4d 70 /* add 0.25 (pi/2) to read sine table */
mbed_official 5:3762170b6d4d 71 x = (uint16_t)x + 0x2000;
mbed_official 5:3762170b6d4d 72 if(x < 0)
mbed_official 5:3762170b6d4d 73 { /* convert negative numbers to corresponding positive ones */
mbed_official 5:3762170b6d4d 74 x = (uint16_t)x + 0x8000;
emilmont 1:fdd22bb7aa52 75 }
emilmont 1:fdd22bb7aa52 76
mbed_official 5:3762170b6d4d 77 /* Calculate the nearest index */
mbed_official 5:3762170b6d4d 78 index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
emilmont 1:fdd22bb7aa52 79
mbed_official 5:3762170b6d4d 80 /* Calculation of fractional value */
mbed_official 5:3762170b6d4d 81 fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
emilmont 1:fdd22bb7aa52 82
mbed_official 5:3762170b6d4d 83 /* Read two nearest values of input value from the sin table */
mbed_official 5:3762170b6d4d 84 a = sinTable_q15[index];
mbed_official 5:3762170b6d4d 85 b = sinTable_q15[index+1];
emilmont 1:fdd22bb7aa52 86
mbed_official 5:3762170b6d4d 87 /* Linear interpolation process */
mbed_official 5:3762170b6d4d 88 cosVal = (q31_t)(0x8000-fract)*a >> 16;
mbed_official 5:3762170b6d4d 89 cosVal = (q15_t)((((q31_t)cosVal << 16) + ((q31_t)fract*b)) >> 16);
emilmont 1:fdd22bb7aa52 90
mbed_official 5:3762170b6d4d 91 return cosVal << 1;
emilmont 1:fdd22bb7aa52 92 }
emilmont 1:fdd22bb7aa52 93
mbed_official 5:3762170b6d4d 94 /**
mbed_official 5:3762170b6d4d 95 * @} end of cos group
emilmont 1:fdd22bb7aa52 96 */