Jaeyoung-Lim · Jaeyoung-Lim · Apr 2, 2023 · Dec 3, 2022 · Dec 4, 2022 · Dec 4, 2022
diff --git a/doc/ROS2_PX4_Offboard_Tutorial.md b/doc/ROS2_PX4_Offboard_Tutorial.md
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+
+## Overview
+
+This tutorial explains how to interface ROS2 with PX4 (SITL) using DDS.
+
+### Prerequisites
+
+   * [ROS2 Installed](https://docs.px4.io/main/en/ros/ros2_comm.html#install-ros-2), and setup for your operating system (e.g. [Linux Ubuntu](https://docs.px4.io/main/en/dev_setup/dev_env_linux_ubuntu.html)) with Gazebo
+   * [FastDDS Installed](https://docs.px4.io/main/en/dev_setup/fast-dds-installation.html)
+   * [PX4-Autopilot downloaded](https://docs.px4.io/main/en/dev_setup/building_px4.html)
+   * [QGroundControl installed](https://docs.qgroundcontrol.com/master/en/getting_started/download_and_install.html)
+
+### Example System Details
+
+  * Ubuntu 22.02
-  * Ubuntu 22.02
+  * Ubuntu 22.04
-  * Ubuntu 22.02
+  * Ubuntu 22.04
+  * ROS2 Humble
+  * Python 3.10
+
+## Install PX4 Offboard and dependencies (one time setup)
+
+### Install the px4-offboard example from Jaeyoung-Lim
+
+```
+cd ~
+git clone https://github.com/Jaeyoung-Lim/px4-offboard.git
+```
+
+### Install PX4 ROS Com and PX4 msg
+
+The `px4-offboard` example requires the `px4_ros_com` bridge and `px4_msgs` definitions:
+
+```
+cd ~
+mkdir px4_ros_com_ws
+cd px4_ros_com_ws
-cd px4_ros_com_ws
+cd <colcon_workspace_path>
-cd px4_ros_com_ws
+cd <colcon_workspace_path>
+git clone https://github.com/PX4/px4_ros_com.git
+git clone https://github.com/PX4/px4_msgs.git
+```
+
+
+Build them:
+
+
+```
+colcon build
+```
+
+This should build, and you may see some warnings:
+
+![](img/20221203161905.png)
+
+As long as there are no __*errors*__ you should be OK..
+
+## Install the micro_ros_agent  (one time setup)
+
+#### Check ROS Distro
+
+When building micro_ros_agent, you need to build it for the particular ROS version you are using.  
+
+Ensure your ROS_DISTRO environment variable is set
+
+```
+env | grep ROS
+```
+
+You should see this variable with some other ROS settings:
+
+```
+ROS_DISTRO=humble
+```
+
+If it's not set you can try to update:
+
+```
+export ROS_DISTRO=humble
+```
+
+
+*Note: If the ROS_DISTRO isn't set in your enviornment you probably don't have a clean ROS2 installation.  You may have issues with the rest of this tutorial.  Recommend reinstalling and checking your ROS2 installation*
+
+
+#### Building the micro_ros_agent
+
+From:  [Building micro-ROS-Agent](https://github.com/micro-ROS/micro_ros_setup#building-micro-ros-agent)
+
+```
+cd ~
+mkdir ~/microros_ws
+cd microros_ws
+git clone -b $ROS_DISTRO https://github.com/micro-ROS/micro_ros_setup.git 
+mkdir src
+mv micro_ros_setup/ src/
+colcon build
+source install/local_setup.sh
+ros2 run micro_ros_setup create_agent_ws.sh
+ros2 run micro_ros_setup build_agent.sh
+```
+*Note how the ROS_DISTRO environment variable is used to specify the correct branch...
+
+This should build and may flash a few warnings:
+
+![](./img/20221203160304.png)
+
+Try running the agent:
+
+```
+source install/local_setup.sh
+ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888
+```
+
+It should respond with:
+
+```
+[1670101284.566587] info     | UDPv4AgentLinux.cpp | init                     | running...             | port: 8888
+[1670101284.566822] info     | Root.cpp           | set_verbose_level        | logger setup           | verbose_level: 4
+```
+
+## Run the Demo
+
+### Overview
+
+You will need 4 terminal windows  ([gnome terminator](https://gnome-terminator.org/) is a great for this!), one for each of the following components:
+
+   * micro-ros-agent
+   * Gazebo   
+   * px4-offboard example
+   * QGroundControl
+
+In each terminal window, we will first source any workspace settings required for a particular component and also set the `ROS_DOMAIN_ID` and `PYTHONOPTIMIZE`  in each window
+
+### Start the micro-ros-agent
+
+```
+cd ~/microros_ws
+export ROS_DOMAIN_ID=0
+export PYTHONOPTIMIZE=1
+ros2 run micro_ros_agent micro_ros_agent udp4 --port 8888 ROS_DOMAIN_ID=0
+```
+
+This should start with a few initial messages:
+
+![](img/20221203163612.png)
+
+### Start Gazebo
+
+```
+cd ~/PX4-Autopilot
+export ROS_DOMAIN_ID=0
+export PYTHONOPTIMIZE=1
+make px4_sitl gazebo
+```
+
+Gazebo should start and you should see the Micro ROS Agent start to receive DDS messages:
+
+![[Pasted image 20221203164029.png]]
+
+Leave the agent running for the rest of the tutorial
+
+If you scroll up in the Gazebo window, you should also see it sending microDDS messages:
+
+![](img/20221203164126.png)
+
+
+### Start QGround Controller and Take Off
+
+In the QGroundControl terminal, launch the app:
+
+```
+./QGroundControl.AppImage
+```
+
+![](img/20221203165425.png)
+
+The simulated drone should takeoff and climb to an altitude of 10m (~32ft)
+
+
+### Start the px4-offboard example
+
+#### Check ROS Messages
+
+Before we start the example, lets check ROS2 topics:
+
+```
+cd ~/px4-offboard
+export ROS_DOMAIN_ID=0
+export PYTHONOPTIMIZE=1
+ros2 topic list
+```
+
+You should see a list of topics that match the ones sent from Gazebo.:
+
+![](img/20221203164701.png)
+
+If you do not see the topics:
+
+  * Check that `ROS_DOMAIN_ID=0`  in all the terminals
+
+Let's echo a  topic:
+
+```
+ros2 topic echo /fmu/out/vehicle_odometry
+```
+
+The terminal should echo some rapidly updating details about the simulated drone.  If you look at position, you can see it matches the height of our drone
+
+![](img/20221203165710.png)
+
+Now that we verfied the DDS-ROS subscription comms, we can start the demo
+
+CTRL-C to stop the topic echo and then:
+
+```
+source ../px4_ros_com_ws/install/setup.bash
+source install/setup.bash
+```
+
+The first source ensures the dependencies are loaded for the demo.
+The second is for the demo itself.
+
+Now launch the demo:
+
+```
+ros2 launch px4_offboard offboard_position_control.launch.py
+```
+
+If things work, the demo should immediately show an RViz window with the drone at altitude:
+
+![](img/20221203170359.png)
+
+Now head back to QGroundControl and enable offboard control.  Click the current mode:
+
+![](img/20221203171934.png)
+
+Then, in the menu, select `Offboard`:
+
+![](img/20221203170522.png)
+
+After a 1-2 sec pause, the demo should take control:
+
+![](img/20221203170609.png)
+
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