Add a Group of Parameters in PX4-Autopilot Firmware and visualize them in QGroundControl

</aside>

Introduction

Parameters are an important part of the environment that PX4 offers, helps us to tune the controller, estimators, or many more options that the firmware has.

Nonetheless, if you are building on top on PX4, it would be great to add some custom parameters to your project.

In this entry, I will show you how to add a group of parameters into the PX4 Firmware, upload it to a pixhawk autopilot, and visualize the custom parameters into the ground station.

Note: This tutorial works for firmware version 1.14 (only tested in this version) due to being the last version supported by the PX4 Toolbox by Mathworks.

#pragma once

#include <px4_platform_common/module.h> #include <px4_platform_common/module_params.h> #include <uORB/SubscriptionInterval.hpp> #include <uORB/topics/parameter_update.h>

using namespace time_literals;

extern "C" __EXPORT int fah_ctrl_main(int argc, char *argv[]);

class FAH_CTRL : public ModuleBase<FAH_CTRL>, public ModuleParams { public: FAH_CTRL(int example_param, bool example_flag);

virtual ~FAH_CTRL() = default;

static int task_spawn(int argc, char *argv[]);

static FAH_CTRL *instantiate(int argc, char *argv[]);

static int print_usage(const char *reason = nullptr);

static int custom_command(int argc, char *argv[]);

void run() override;

int print_status() override;

private: void parameters_update(bool force = false);

DEFINE_PARAMETERS(
    (ParamFloat<px4::params::FAH_X_P>) _fah_x_p,
    (ParamFloat<px4::params::FAH_X_D>) _fah_x_d,
    (ParamFloat<px4::params::FAH_X_I>) _fah_x_i,
    (ParamFloat<px4::params::FAH_Y_P>) _fah_y_p,
    (ParamFloat<px4::params::FAH_Y_D>) _fah_y_d,
    (ParamFloat<px4::params::FAH_Y_I>) _fah_y_i,
    (ParamFloat<px4::params::FAH_Z_P>) _fah_z_p,
    (ParamFloat<px4::params::FAH_Z_D>) _fah_z_d,
    (ParamFloat<px4::params::FAH_Z_I>) _fah_z_i,

    (ParamFloat<px4::params::FAH_ROLL_P>) _fah_roll_p,
    (ParamFloat<px4::params::FAH_ROLL_I>) _fah_roll_i,
    (ParamFloat<px4::params::FAH_ROLL_D>) _fah_roll_d,
    (ParamFloat<px4::params::FAH_PITCH_P>) _fah_pitch_p,
    (ParamFloat<px4::params::FAH_PITCH_I>) _fah_pitch_i,
    (ParamFloat<px4::params::FAH_PITCH_D>) _fah_pitch_d,
    (ParamFloat<px4::params::FAH_YAW_P>) _fah_yaw_p,
    (ParamFloat<px4::params::FAH_YAW_I>) _fah_yaw_i,
    (ParamFloat<px4::params::FAH_YAW_D>) _fah_yaw_d,

    (ParamFloat<px4::params::FAH_MASS>) _fah_mass,
    (ParamFloat<px4::params::FAH_I_XX>) _fah_i_xx,
    (ParamFloat<px4::params::FAH_I_YY>) _fah_i_yy,
    (ParamFloat<px4::params::FAH_I_ZZ>) _fah_i_zz,
(ParamFloat<px4::params::FAH_ALT_DES>) _fah_alt_des,
(ParamFloat<px4::params::FAH_X_DES>) _fah_x_des,
(ParamFloat<px4::params::FAH_Y_DES>) _fah_y_des,
(ParamInt<px4::params::TRAJ_SEL>) _traj_sel,
(ParamInt<px4::params::CTRL_SEL>) _ctrl_sel,
(ParamInt<px4::params::EST_SEL>) _est_sel,

(ParamFloat<px4::params::X_XI1>) _x_xi1,
(ParamFloat<px4::params::X_XI2>) _x_xi2,
(ParamFloat<px4::params::X_LAM1>) _x_lam1,
(ParamFloat<px4::params::X_LAM2>) _x_lam2,
(ParamFloat<px4::params::X_ALPHA_U>) _x_alpha_u,
(ParamFloat<px4::params::X_BETA_U>) _x_beta_u,
(ParamFloat<px4::params::X_EPS_U>) _x_eps_u,

(ParamFloat<px4::params::Y_XI1>) _y_xi1,
(ParamFloat<px4::params::Y_XI2>) _y_xi2,
(ParamFloat<px4::params::Y_LAM1>) _y_lam1,
(ParamFloat<px4::params::Y_LAM2>) _y_lam2,
(ParamFloat<px4::params::Y_ALPHA_U>) _y_alpha_u,
(ParamFloat<px4::params::Y_BETA_U>) _y_beta_u,
(ParamFloat<px4::params::Y_EPS_U>) _y_eps_u,

(ParamFloat<px4::params::Z_XI1>) _z_xi1,
(ParamFloat<px4::params::Z_XI2>) _z_xi2,
(ParamFloat<px4::params::Z_LAM1>) _z_lam1,
(ParamFloat<px4::params::Z_LAM2>) _z_lam2,
(ParamFloat<px4::params::Z_ALPHA_U>) _z_alpha_u,
(ParamFloat<px4::params::Z_BETA_U>) _z_beta_u,
(ParamFloat<px4::params::Z_EPS_U>) _z_eps_u,

(ParamFloat<px4::params::ROLL_XI1>) _roll_xi1,
(ParamFloat<px4::params::ROLL_XI2>) _roll_xi2,
(ParamFloat<px4::params::ROLL_LAM1>) _roll_lam1,
(ParamFloat<px4::params::ROLL_LAM2>) _roll_lam2,
(ParamFloat<px4::params::ROLL_ALPHA_U>) _roll_alpha_u,
(ParamFloat<px4::params::ROLL_BETA_U>) _roll_beta_u,
(ParamFloat<px4::params::ROLL_EPS_U>) _roll_eps_u,

(ParamFloat<px4::params::PITCH_XI1>) _pitch_xi1,
(ParamFloat<px4::params::PITCH_XI2>) _pitch_xi2,
(ParamFloat<px4::params::PITCH_LAM1>) _pitch_lam1,
(ParamFloat<px4::params::PITCH_LAM2>) _pitch_lam2,
(ParamFloat<px4::params::PITCH_ALPHA_U>) _pitch_alpha_u,
(ParamFloat<px4::params::PITCH_BETA_U>) _pitch_beta_u,
(ParamFloat<px4::params::PITCH_EPS_U>) _pitch_eps_u,

(ParamFloat<px4::params::YAW_XI1>) _yaw_xi1,
(ParamFloat<px4::params::YAW_XI2>) _yaw_xi2,
(ParamFloat<px4::params::YAW_LAM1>) _yaw_lam1,
(ParamFloat<px4::params::YAW_LAM2>) _yaw_lam2,
(ParamFloat<px4::params::YAW_ALPHA_U>) _yaw_alpha_u,
(ParamFloat<px4::params::YAW_BETA_U>) _yaw_beta_u,
(ParamFloat<px4::params::YAW_EPS_U>) _yaw_eps_u,
(ParamFloat<px4::params::CTRL0>) _ctrl0,
(ParamFloat<px4::params::CTRL1>) _ctrl1

)

uORB::SubscriptionInterval _parameter_update_sub{ORB_ID(parameter_update), 1_s};

};

</aside>

Adding a new Module based on the TemplateModule

Before the tutorial

Note: This tutorial is tested for version 1.14 (and 1.14.3), and that you already have the code cloned for the official repo in a folder named PX4-Autopilot (if you git clone as usual this should be the case).

Part of this steps are based on [2] on how to create a Module in PX4-Autopilot.
Create a new folder in PX4-Autopilot/src/modules named as you wish, all in underscores, and touch the following files:

mkdir fah_ctrl
cd fah_ctrl
touch CMakeLists.txt
touch Kconfig
touch module.yaml
touch fah_ctrl.cpp
touch fah_ctrl.h

Each of this files take an important part in defining the module in the PX4 environment, as well as defining the new parameters

CMakeLists.txt

Based on the PX4 Documentation, the content of this file is:

px4_add_module(
	MODULE modules__fah_ctrl
	MAIN fah_ctrl
	SRCS
	    fah_ctrl.cpp
	MODULE_CONFIG
	    module.yaml
	)