John Garlitos / Mbed OS EVAL-CN0540-ARDZ

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Dependencies:   platform_drivers LTC26X6 AD77681

CMSIS-DSP_Lib/Source/FastMathFunctions/arm_sqrt_q15.c@1:9dd7c64b4a64, 2021-12-06 (annotated)

Committer:
jngarlitos
Date:
Mon Dec 06 05:22:28 2021 +0000
Revision:
1:9dd7c64b4a64
EVAL-CN0540-ARDZ mbed example program Initial Commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
jngarlitos 1:9dd7c64b4a64 1 /* ----------------------------------------------------------------------
jngarlitos 1:9dd7c64b4a64 2 * Copyright (C) 2010-2014 ARM Limited. All rights reserved.
jngarlitos 1:9dd7c64b4a64 3 *
jngarlitos 1:9dd7c64b4a64 4 * $Date: 19. October 2015
jngarlitos 1:9dd7c64b4a64 5 * $Revision: V.1.4.5 a
jngarlitos 1:9dd7c64b4a64 6 *
jngarlitos 1:9dd7c64b4a64 7 * Project: CMSIS DSP Library
jngarlitos 1:9dd7c64b4a64 8 * Title: arm_sqrt_q15.c
jngarlitos 1:9dd7c64b4a64 9 *
jngarlitos 1:9dd7c64b4a64 10 * Description: Q15 square root function.
jngarlitos 1:9dd7c64b4a64 11 *
jngarlitos 1:9dd7c64b4a64 12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
jngarlitos 1:9dd7c64b4a64 13 *
jngarlitos 1:9dd7c64b4a64 14 * Redistribution and use in source and binary forms, with or without
jngarlitos 1:9dd7c64b4a64 15 * modification, are permitted provided that the following conditions
jngarlitos 1:9dd7c64b4a64 16 * are met:
jngarlitos 1:9dd7c64b4a64 17 * - Redistributions of source code must retain the above copyright
jngarlitos 1:9dd7c64b4a64 18 * notice, this list of conditions and the following disclaimer.
jngarlitos 1:9dd7c64b4a64 19 * - Redistributions in binary form must reproduce the above copyright
jngarlitos 1:9dd7c64b4a64 20 * notice, this list of conditions and the following disclaimer in
jngarlitos 1:9dd7c64b4a64 21 * the documentation and/or other materials provided with the
jngarlitos 1:9dd7c64b4a64 22 * distribution.
jngarlitos 1:9dd7c64b4a64 23 * - Neither the name of ARM LIMITED nor the names of its contributors
jngarlitos 1:9dd7c64b4a64 24 * may be used to endorse or promote products derived from this
jngarlitos 1:9dd7c64b4a64 25 * software without specific prior written permission.
jngarlitos 1:9dd7c64b4a64 26 *
jngarlitos 1:9dd7c64b4a64 27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
jngarlitos 1:9dd7c64b4a64 28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
jngarlitos 1:9dd7c64b4a64 29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
jngarlitos 1:9dd7c64b4a64 30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
jngarlitos 1:9dd7c64b4a64 31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
jngarlitos 1:9dd7c64b4a64 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
jngarlitos 1:9dd7c64b4a64 33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
jngarlitos 1:9dd7c64b4a64 34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
jngarlitos 1:9dd7c64b4a64 35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
jngarlitos 1:9dd7c64b4a64 36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
jngarlitos 1:9dd7c64b4a64 37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
jngarlitos 1:9dd7c64b4a64 38 * POSSIBILITY OF SUCH DAMAGE.
jngarlitos 1:9dd7c64b4a64 39 * -------------------------------------------------------------------- */
jngarlitos 1:9dd7c64b4a64 40 #include "arm_math.h"
jngarlitos 1:9dd7c64b4a64 41 #include "arm_common_tables.h"
jngarlitos 1:9dd7c64b4a64 42
jngarlitos 1:9dd7c64b4a64 43
jngarlitos 1:9dd7c64b4a64 44 /**
jngarlitos 1:9dd7c64b4a64 45 * @ingroup groupFastMath
jngarlitos 1:9dd7c64b4a64 46 */
jngarlitos 1:9dd7c64b4a64 47
jngarlitos 1:9dd7c64b4a64 48 /**
jngarlitos 1:9dd7c64b4a64 49 * @addtogroup SQRT
jngarlitos 1:9dd7c64b4a64 50 * @{
jngarlitos 1:9dd7c64b4a64 51 */
jngarlitos 1:9dd7c64b4a64 52
jngarlitos 1:9dd7c64b4a64 53 /**
jngarlitos 1:9dd7c64b4a64 54 * @brief Q15 square root function.
jngarlitos 1:9dd7c64b4a64 55 * @param[in] in input value. The range of the input value is [0 +1) or 0x0000 to 0x7FFF.
jngarlitos 1:9dd7c64b4a64 56 * @param[out] *pOut square root of input value.
jngarlitos 1:9dd7c64b4a64 57 * @return The function returns ARM_MATH_SUCCESS if the input value is positive
jngarlitos 1:9dd7c64b4a64 58 * and ARM_MATH_ARGUMENT_ERROR if the input is negative. For
jngarlitos 1:9dd7c64b4a64 59 * negative inputs, the function returns *pOut = 0.
jngarlitos 1:9dd7c64b4a64 60 */
jngarlitos 1:9dd7c64b4a64 61
jngarlitos 1:9dd7c64b4a64 62 arm_status arm_sqrt_q15(
jngarlitos 1:9dd7c64b4a64 63 q15_t in,
jngarlitos 1:9dd7c64b4a64 64 q15_t * pOut)
jngarlitos 1:9dd7c64b4a64 65 {
jngarlitos 1:9dd7c64b4a64 66 q15_t number, temp1, var1, signBits1, half;
jngarlitos 1:9dd7c64b4a64 67 q31_t bits_val1;
jngarlitos 1:9dd7c64b4a64 68 float32_t temp_float1;
jngarlitos 1:9dd7c64b4a64 69 union
jngarlitos 1:9dd7c64b4a64 70 {
jngarlitos 1:9dd7c64b4a64 71 q31_t fracval;
jngarlitos 1:9dd7c64b4a64 72 float32_t floatval;
jngarlitos 1:9dd7c64b4a64 73 } tempconv;
jngarlitos 1:9dd7c64b4a64 74
jngarlitos 1:9dd7c64b4a64 75 number = in;
jngarlitos 1:9dd7c64b4a64 76
jngarlitos 1:9dd7c64b4a64 77 /* If the input is a positive number then compute the signBits. */
jngarlitos 1:9dd7c64b4a64 78 if(number > 0)
jngarlitos 1:9dd7c64b4a64 79 {
jngarlitos 1:9dd7c64b4a64 80 signBits1 = __CLZ(number) - 17;
jngarlitos 1:9dd7c64b4a64 81
jngarlitos 1:9dd7c64b4a64 82 /* Shift by the number of signBits1 */
jngarlitos 1:9dd7c64b4a64 83 if((signBits1 % 2) == 0)
jngarlitos 1:9dd7c64b4a64 84 {
jngarlitos 1:9dd7c64b4a64 85 number = number << signBits1;
jngarlitos 1:9dd7c64b4a64 86 }
jngarlitos 1:9dd7c64b4a64 87 else
jngarlitos 1:9dd7c64b4a64 88 {
jngarlitos 1:9dd7c64b4a64 89 number = number << (signBits1 - 1);
jngarlitos 1:9dd7c64b4a64 90 }
jngarlitos 1:9dd7c64b4a64 91
jngarlitos 1:9dd7c64b4a64 92 /* Calculate half value of the number */
jngarlitos 1:9dd7c64b4a64 93 half = number >> 1;
jngarlitos 1:9dd7c64b4a64 94 /* Store the number for later use */
jngarlitos 1:9dd7c64b4a64 95 temp1 = number;
jngarlitos 1:9dd7c64b4a64 96
jngarlitos 1:9dd7c64b4a64 97 /* Convert to float */
jngarlitos 1:9dd7c64b4a64 98 temp_float1 = number * 3.051757812500000e-005f;
jngarlitos 1:9dd7c64b4a64 99 /*Store as integer */
jngarlitos 1:9dd7c64b4a64 100 tempconv.floatval = temp_float1;
jngarlitos 1:9dd7c64b4a64 101 bits_val1 = tempconv.fracval;
jngarlitos 1:9dd7c64b4a64 102 /* Subtract the shifted value from the magic number to give intial guess */
jngarlitos 1:9dd7c64b4a64 103 bits_val1 = 0x5f3759df - (bits_val1 >> 1); /* gives initial guess */
jngarlitos 1:9dd7c64b4a64 104 /* Store as float */
jngarlitos 1:9dd7c64b4a64 105 tempconv.fracval = bits_val1;
jngarlitos 1:9dd7c64b4a64 106 temp_float1 = tempconv.floatval;
jngarlitos 1:9dd7c64b4a64 107 /* Convert to integer format */
jngarlitos 1:9dd7c64b4a64 108 var1 = (q31_t) (temp_float1 * 16384);
jngarlitos 1:9dd7c64b4a64 109
jngarlitos 1:9dd7c64b4a64 110 /* 1st iteration */
jngarlitos 1:9dd7c64b4a64 111 var1 = ((q15_t) ((q31_t) var1 * (0x3000 -
jngarlitos 1:9dd7c64b4a64 112 ((q15_t)
jngarlitos 1:9dd7c64b4a64 113 ((((q15_t)
jngarlitos 1:9dd7c64b4a64 114 (((q31_t) var1 * var1) >> 15)) *
jngarlitos 1:9dd7c64b4a64 115 (q31_t) half) >> 15))) >> 15)) << 2;
jngarlitos 1:9dd7c64b4a64 116 /* 2nd iteration */
jngarlitos 1:9dd7c64b4a64 117 var1 = ((q15_t) ((q31_t) var1 * (0x3000 -
jngarlitos 1:9dd7c64b4a64 118 ((q15_t)
jngarlitos 1:9dd7c64b4a64 119 ((((q15_t)
jngarlitos 1:9dd7c64b4a64 120 (((q31_t) var1 * var1) >> 15)) *
jngarlitos 1:9dd7c64b4a64 121 (q31_t) half) >> 15))) >> 15)) << 2;
jngarlitos 1:9dd7c64b4a64 122 /* 3rd iteration */
jngarlitos 1:9dd7c64b4a64 123 var1 = ((q15_t) ((q31_t) var1 * (0x3000 -
jngarlitos 1:9dd7c64b4a64 124 ((q15_t)
jngarlitos 1:9dd7c64b4a64 125 ((((q15_t)
jngarlitos 1:9dd7c64b4a64 126 (((q31_t) var1 * var1) >> 15)) *
jngarlitos 1:9dd7c64b4a64 127 (q31_t) half) >> 15))) >> 15)) << 2;
jngarlitos 1:9dd7c64b4a64 128
jngarlitos 1:9dd7c64b4a64 129 /* Multiply the inverse square root with the original value */
jngarlitos 1:9dd7c64b4a64 130 var1 = ((q15_t) (((q31_t) temp1 * var1) >> 15)) << 1;
jngarlitos 1:9dd7c64b4a64 131
jngarlitos 1:9dd7c64b4a64 132 /* Shift the output down accordingly */
jngarlitos 1:9dd7c64b4a64 133 if((signBits1 % 2) == 0)
jngarlitos 1:9dd7c64b4a64 134 {
jngarlitos 1:9dd7c64b4a64 135 var1 = var1 >> (signBits1 / 2);
jngarlitos 1:9dd7c64b4a64 136 }
jngarlitos 1:9dd7c64b4a64 137 else
jngarlitos 1:9dd7c64b4a64 138 {
jngarlitos 1:9dd7c64b4a64 139 var1 = var1 >> ((signBits1 - 1) / 2);
jngarlitos 1:9dd7c64b4a64 140 }
jngarlitos 1:9dd7c64b4a64 141 *pOut = var1;
jngarlitos 1:9dd7c64b4a64 142
jngarlitos 1:9dd7c64b4a64 143 return (ARM_MATH_SUCCESS);
jngarlitos 1:9dd7c64b4a64 144 }
jngarlitos 1:9dd7c64b4a64 145 /* If the number is a negative number then store zero as its square root value */
jngarlitos 1:9dd7c64b4a64 146 else
jngarlitos 1:9dd7c64b4a64 147 {
jngarlitos 1:9dd7c64b4a64 148 *pOut = 0;
jngarlitos 1:9dd7c64b4a64 149 return (ARM_MATH_ARGUMENT_ERROR);
jngarlitos 1:9dd7c64b4a64 150 }
jngarlitos 1:9dd7c64b4a64 151 }
jngarlitos 1:9dd7c64b4a64 152
jngarlitos 1:9dd7c64b4a64 153 /**
jngarlitos 1:9dd7c64b4a64 154 * @} end of SQRT group
jngarlitos 1:9dd7c64b4a64 155 */