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/****************************************************************************
*
* Copyright (C) 2012 PX4 Development Team. All rights reserved.
* 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.h
* Definition of commonly used conversions.
*
* Includes bit / byte / geo representation and unit conversions.
*/
#ifndef CONVERSIONS_H_
#define CONVERSIONS_H_
#include <float.h>
#include <stdint.h>
#define CONSTANTS_ONE_G 9.80665f // m/s^2
#define CONSTANTS_AIR_DENSITY_SEA_LEVEL_15C 1.225f // kg/m^3
#define CONSTANTS_AIR_GAS_CONST 287.1f // J/(kg * K)
#define CONSTANTS_ABSOLUTE_NULL_CELSIUS -273.15f // °C
__BEGIN_DECLS
/**
* Converts a signed 16 bit integer from big endian to little endian.
*
* This function is for commonly used 16 bit big endian sensor data,
* delivered by driver routines as two 8 bit numbers in big endian order.
* Common vendors with big endian representation are Invense, Bosch and
* Honeywell. ST micro devices tend to use a little endian representation.
*/
__EXPORT int16_t int16_t_from_bytes(uint8_t bytes[]);
/**
* Converts a 3 x 3 rotation matrix to an unit quaternion.
*
* All orientations are expressed in NED frame.
*
* @param R rotation matrix to convert
* @param Q quaternion to write back to
*/
__EXPORT void rot2quat(const float R[9], float Q[4]);
/**
* Converts an unit quaternion to a 3 x 3 rotation matrix.
*
* All orientations are expressed in NED frame.
*
* @param Q quaternion to convert
* @param R rotation matrix to write back to
*/
__EXPORT void quat2rot(const float Q[4], float R[9]);
/**
* Calculates air density.
*
* @param static_pressure ambient pressure in millibar
* @param temperature_celcius air / ambient temperature in celcius
*/
__EXPORT float get_air_density(float static_pressure, float temperature_celsius);
__END_DECLS
#endif /* CONVERSIONS_H_ */
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