forked from Archive/PX4-Autopilot
155 lines
4.1 KiB
C
155 lines
4.1 KiB
C
/****************************************************************************
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*
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* Copyright (C) 2012 PX4 Development Team. All rights reserved.
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* Author: @author Lorenz Meier <lm@inf.ethz.ch>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name PX4 nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file conversions.c
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* Implementation of commonly used conversions.
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*/
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#include <nuttx/config.h>
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#include <float.h>
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#include "conversions.h"
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int16_t
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int16_t_from_bytes(uint8_t bytes[])
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{
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union {
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uint8_t b[2];
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int16_t w;
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} u;
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u.b[1] = bytes[0];
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u.b[0] = bytes[1];
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return u.w;
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}
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void rot2quat(const float R[9], float Q[4])
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{
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float q0_2;
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float q1_2;
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float q2_2;
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float q3_2;
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int32_t idx;
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/* conversion of rotation matrix to quaternion
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* choose the largest component to begin with */
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q0_2 = (((1.0F + R[0]) + R[4]) + R[8]) / 4.0F;
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q1_2 = (((1.0F + R[0]) - R[4]) - R[8]) / 4.0F;
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q2_2 = (((1.0F - R[0]) + R[4]) - R[8]) / 4.0F;
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q3_2 = (((1.0F - R[0]) - R[4]) + R[8]) / 4.0F;
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idx = 0;
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if (q0_2 < q1_2) {
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q0_2 = q1_2;
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idx = 1;
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}
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if (q0_2 < q2_2) {
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q0_2 = q2_2;
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idx = 2;
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}
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if (q0_2 < q3_2) {
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q0_2 = q3_2;
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idx = 3;
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}
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q0_2 = sqrtf(q0_2);
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/* solve for the remaining three components */
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if (idx == 0) {
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q1_2 = q0_2;
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q2_2 = (R[5] - R[7]) / 4.0F / q0_2;
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q3_2 = (R[6] - R[2]) / 4.0F / q0_2;
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q0_2 = (R[1] - R[3]) / 4.0F / q0_2;
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} else if (idx == 1) {
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q2_2 = q0_2;
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q1_2 = (R[5] - R[7]) / 4.0F / q0_2;
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q3_2 = (R[3] + R[1]) / 4.0F / q0_2;
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q0_2 = (R[6] + R[2]) / 4.0F / q0_2;
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} else if (idx == 2) {
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q3_2 = q0_2;
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q1_2 = (R[6] - R[2]) / 4.0F / q0_2;
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q2_2 = (R[3] + R[1]) / 4.0F / q0_2;
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q0_2 = (R[7] + R[5]) / 4.0F / q0_2;
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} else {
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q1_2 = (R[1] - R[3]) / 4.0F / q0_2;
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q2_2 = (R[6] + R[2]) / 4.0F / q0_2;
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q3_2 = (R[7] + R[5]) / 4.0F / q0_2;
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}
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/* return values */
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Q[0] = q1_2;
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Q[1] = q2_2;
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Q[2] = q3_2;
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Q[3] = q0_2;
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}
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void quat2rot(const float Q[4], float R[9])
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{
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float q0_2;
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float q1_2;
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float q2_2;
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float q3_2;
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memset(&R[0], 0, 9U * sizeof(float));
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q0_2 = Q[0] * Q[0];
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q1_2 = Q[1] * Q[1];
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q2_2 = Q[2] * Q[2];
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q3_2 = Q[3] * Q[3];
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R[0] = ((q0_2 + q1_2) - q2_2) - q3_2;
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R[3] = 2.0F * (Q[1] * Q[2] - Q[0] * Q[3]);
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R[6] = 2.0F * (Q[1] * Q[3] + Q[0] * Q[2]);
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R[1] = 2.0F * (Q[1] * Q[2] + Q[0] * Q[3]);
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R[4] = ((q0_2 + q2_2) - q1_2) - q3_2;
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R[7] = 2.0F * (Q[2] * Q[3] - Q[0] * Q[1]);
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R[2] = 2.0F * (Q[1] * Q[3] - Q[0] * Q[2]);
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R[5] = 2.0F * (Q[2] * Q[3] + Q[0] * Q[1]);
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R[8] = ((q0_2 + q3_2) - q1_2) - q2_2;
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}
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float get_air_density(float static_pressure, float temperature_celsius)
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{
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return static_pressure / (CONSTANTS_AIR_GAS_CONST * (temperature_celsius - CONSTANTS_ABSOLUTE_NULL_CELSIUS));
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}
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