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