Robert Lopez / CMSIS5

Aded CMSIS5 DSP and NN folder. Needs some work

DSP/source/FastMathFunctions/arm_cos_q15.c@0:eedb7d567a5d, 2018-04-12 (annotated)

Committer:
robert_lp
Date:
Thu Apr 12 01:31:58 2018 +0000
Revision:
0:eedb7d567a5d
CMSIS5 Library

Who changed what in which revision?

UserRevisionLine numberNew contents of line
robert_lp 0:eedb7d567a5d 1 /* ----------------------------------------------------------------------
robert_lp 0:eedb7d567a5d 2 * Project: CMSIS DSP Library
robert_lp 0:eedb7d567a5d 3 * Title: arm_cos_q15.c
robert_lp 0:eedb7d567a5d 4 * Description: Fast cosine calculation for Q15 values
robert_lp 0:eedb7d567a5d 5 *
robert_lp 0:eedb7d567a5d 6 * $Date: 27. January 2017
robert_lp 0:eedb7d567a5d 7 * $Revision: V.1.5.1
robert_lp 0:eedb7d567a5d 8 *
robert_lp 0:eedb7d567a5d 9 * Target Processor: Cortex-M cores
robert_lp 0:eedb7d567a5d 10 * -------------------------------------------------------------------- */
robert_lp 0:eedb7d567a5d 11 /*
robert_lp 0:eedb7d567a5d 12 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
robert_lp 0:eedb7d567a5d 13 *
robert_lp 0:eedb7d567a5d 14 * SPDX-License-Identifier: Apache-2.0
robert_lp 0:eedb7d567a5d 15 *
robert_lp 0:eedb7d567a5d 16 * Licensed under the Apache License, Version 2.0 (the License); you may
robert_lp 0:eedb7d567a5d 17 * not use this file except in compliance with the License.
robert_lp 0:eedb7d567a5d 18 * You may obtain a copy of the License at
robert_lp 0:eedb7d567a5d 19 *
robert_lp 0:eedb7d567a5d 20 * www.apache.org/licenses/LICENSE-2.0
robert_lp 0:eedb7d567a5d 21 *
robert_lp 0:eedb7d567a5d 22 * Unless required by applicable law or agreed to in writing, software
robert_lp 0:eedb7d567a5d 23 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
robert_lp 0:eedb7d567a5d 24 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
robert_lp 0:eedb7d567a5d 25 * See the License for the specific language governing permissions and
robert_lp 0:eedb7d567a5d 26 * limitations under the License.
robert_lp 0:eedb7d567a5d 27 */
robert_lp 0:eedb7d567a5d 28
robert_lp 0:eedb7d567a5d 29 #include "arm_math.h"
robert_lp 0:eedb7d567a5d 30 #include "arm_common_tables.h"
robert_lp 0:eedb7d567a5d 31
robert_lp 0:eedb7d567a5d 32 /**
robert_lp 0:eedb7d567a5d 33 * @ingroup groupFastMath
robert_lp 0:eedb7d567a5d 34 */
robert_lp 0:eedb7d567a5d 35
robert_lp 0:eedb7d567a5d 36 /**
robert_lp 0:eedb7d567a5d 37 * @addtogroup cos
robert_lp 0:eedb7d567a5d 38 * @{
robert_lp 0:eedb7d567a5d 39 */
robert_lp 0:eedb7d567a5d 40
robert_lp 0:eedb7d567a5d 41 /**
robert_lp 0:eedb7d567a5d 42 * @brief Fast approximation to the trigonometric cosine function for Q15 data.
robert_lp 0:eedb7d567a5d 43 * @param[in] x Scaled input value in radians.
robert_lp 0:eedb7d567a5d 44 * @return cos(x).
robert_lp 0:eedb7d567a5d 45 *
robert_lp 0:eedb7d567a5d 46 * The Q15 input value is in the range [0 +0.9999] and is mapped to a radian
robert_lp 0:eedb7d567a5d 47 * value in the range [0 2*pi).
robert_lp 0:eedb7d567a5d 48 */
robert_lp 0:eedb7d567a5d 49
robert_lp 0:eedb7d567a5d 50 q15_t arm_cos_q15(
robert_lp 0:eedb7d567a5d 51 q15_t x)
robert_lp 0:eedb7d567a5d 52 {
robert_lp 0:eedb7d567a5d 53 q15_t cosVal; /* Temporary variables for input, output */
robert_lp 0:eedb7d567a5d 54 int32_t index; /* Index variables */
robert_lp 0:eedb7d567a5d 55 q15_t a, b; /* Four nearest output values */
robert_lp 0:eedb7d567a5d 56 q15_t fract; /* Temporary values for fractional values */
robert_lp 0:eedb7d567a5d 57
robert_lp 0:eedb7d567a5d 58 /* add 0.25 (pi/2) to read sine table */
robert_lp 0:eedb7d567a5d 59 x = (uint16_t)x + 0x2000;
robert_lp 0:eedb7d567a5d 60 if (x < 0)
robert_lp 0:eedb7d567a5d 61 { /* convert negative numbers to corresponding positive ones */
robert_lp 0:eedb7d567a5d 62 x = (uint16_t)x + 0x8000;
robert_lp 0:eedb7d567a5d 63 }
robert_lp 0:eedb7d567a5d 64
robert_lp 0:eedb7d567a5d 65 /* Calculate the nearest index */
robert_lp 0:eedb7d567a5d 66 index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;
robert_lp 0:eedb7d567a5d 67
robert_lp 0:eedb7d567a5d 68 /* Calculation of fractional value */
robert_lp 0:eedb7d567a5d 69 fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;
robert_lp 0:eedb7d567a5d 70
robert_lp 0:eedb7d567a5d 71 /* Read two nearest values of input value from the sin table */
robert_lp 0:eedb7d567a5d 72 a = sinTable_q15[index];
robert_lp 0:eedb7d567a5d 73 b = sinTable_q15[index+1];
robert_lp 0:eedb7d567a5d 74
robert_lp 0:eedb7d567a5d 75 /* Linear interpolation process */
robert_lp 0:eedb7d567a5d 76 cosVal = (q31_t)(0x8000-fract)*a >> 16;
robert_lp 0:eedb7d567a5d 77 cosVal = (q15_t)((((q31_t)cosVal << 16) + ((q31_t)fract*b)) >> 16);
robert_lp 0:eedb7d567a5d 78
robert_lp 0:eedb7d567a5d 79 return cosVal << 1;
robert_lp 0:eedb7d567a5d 80 }
robert_lp 0:eedb7d567a5d 81
robert_lp 0:eedb7d567a5d 82 /**
robert_lp 0:eedb7d567a5d 83 * @} end of cos group
robert_lp 0:eedb7d567a5d 84 */
robert_lp 0:eedb7d567a5d 85