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Diffstat (limited to 'src/modules/systemlib/conversions.c')
| -rw-r--r-- | src/modules/systemlib/conversions.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/src/modules/systemlib/conversions.c b/src/modules/systemlib/conversions.c new file mode 100644 index 000000000..ac94252c5 --- /dev/null +++ b/src/modules/systemlib/conversions.c @@ -0,0 +1,154 @@ +/**************************************************************************** + * + * 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)); +} |