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6.2 Micro XRCE-DDS

In order for ROS 2 to communicate with PX4, the uXRCE-DDS Client must be running on the PX4 and connected to the Micro XRCE-DDS Agent running on the companion computer, the RDK X5 Module.

Micro XRCE-DDS Client​

The PX4 uxrce_dds_client is generated at build time and included by default in the PX4 firmware; no additional installation is required.

Micro XRCE-DDS Agent​

The Micro XRCE-DDS Agent can be installed on a companion machine using a binary package, built and installed from source code, or built and run within a ROS 2 workspace. All of these methods will get all the dependencies needed to communicate with the client (such as FastCDR).

Installing the standalone​

On Ubuntu, you can build the Agent standalone version from source and install it using the following command:

git clone -b v2.4.2 https://github.com/eProsima/Micro-XRCE-DDS-Agent.git
cd Micro-XRCE-DDS-Agent
mkdir build
cd build
cmake ..
make
sudo make install
sudo ldconfig /usr/local/lib/

To start the proxy and set up a connection to the uXRCE-DDS client running on the emulator:

MicroXRCEAgent udp4 -p 8888

from Snap package​

Install from the snap package on Ubuntu using the following command:

sudo snap install micro-xrce-dds-agent --edge

To start the agent, use the settings that connect to the uXRCE-DDS client running on the emulator (note that the command names are different when you build the agent locally):

micro-xrce-dds-agent udp4 -p 8888

Building/​

You can build and launch the agent within a ROS 2 workspace (or build it standalone and launch it from a workspace). You must have already installed ROS 2 as described in the ROS 2 User Guide > Installing ROS 2.

To build an agent in ROS:

  1. Create a workspace directory for the agent: 
    mkdir -p ~/px4_ros_uxrce_dds_ws/src
  2. Clone the source code of eProsima Micro-XRCE-DDS-Agent to /src the directory ( main default clone branch): 
    cd ~/px4_ros_uxrce_dds_ws/src
    git clone -b v2.4.2 https://github.com/eProsima/Micro-XRCE-DDS-Agent.git
  3. Get the ROS 2 development environment and compile the workspace using the following commands colcon: 
    source /opt/ros/humble/setup.bash
    colcon build
    /src This will build all folders under it using the source toolchain.

To run the Micro XRCE-DDS Agent in a workspace:

  1. Provide the source local_setup.bash to make the executable available in the terminal (even if setup.bash using a new terminal). 
    source /opt/ros/humble/setup.bash
    source install/local_setup.bash
  2. Start the agent with settings that connect to the uXRCE-DDS client running on the emulator: 
    MicroXRCEAgent udp4 -p 8888