Creating a systemd service to auto-start the microRTPS agent on NavQ

Generate a start up script for the micrortps client under /usr/local/bin

with content

Save the file and exit nano. Make the file executable

Generate a systemd service file to start the startup script at boot

with content

Save the file and exit nano. Check if the process starts

You should see an state active (running), quit with <q> Enable the systemd service file finally to be active at boot

Auto-start the microRTPS client on the FMU

Building PX4 with microRTPS

In order to use the microRTPS client on NavQ, you'll need to build PX4 with the _rtps tag for the fmuk66-v3 build target. To do this, you will need to have both the FastRTPS and Fast-RTPS-Gen packages installed. You can just follow the previous guide on your Linux development VM or computer.

Once you have successfully installed those two packages, you can navigate to your cloned PX4 repository and run the following:

Flashing your FMU with the updated binary

You will need to flash your FMU with the updated RTPS binary. If you don't know how to do this yet, follow the guide here:

Creating a startup file on the SD card

To make the microRTPS client start at boot on the FMU, you will need to have an SD card inserted. On your SD card, make a file at /etc/extras.txt and insert one of the following options:

Overview

In this section, we will guide you through the process needed to detect AprilTags on your NavQ. There are a few things that need to be done to accomplish this:

1. Install ROS2 image tools

2. Build and install AprilTag detection nodes

3. Calibrate the camera on your NavQ using a checkerboard pattern

Prerequisites

Before we start, you will need a few things:

Checkerboard

To create a checkerboard for camera calibration, download this PDF:

Desktop Setup

In order to calibrate the camera, you will need to set up your NavQ with a mouse, keyboard, and monitor. Use the included microUSB hub and HDMI connector to do so.

Installing required ROS2 software

Install the following packages with the apt package manager by running the commands below:

Once that is finished, move on to the next step.

Calibrating the camera

Hook up your NavQ to a monitor with the provided HDMI cord and connect a USB mouse + keyboard through the included microUSB hub. Open the terminal by clicking the icon at the top left of the screen and open the bash shell by running:

Have your printed checkerboard ready in a well lit environment and run the camera calibration software by running the following commands:

Now use the link in the note above to run through calibarating the camera.

Detecting AprilTags

Building apriltag_msgs

A prerequisite for the apriltag_ros node is apriltag_msgs. Clone the repo and build it by running these commands:

Make sure to source the install/setup.bash file so that apriltag_msgs can see it when being built.

Building the apriltag_ros node

First, in order to detect AprilTags, we need to build the apriltag_ros node written by christianrauch. You can clone his repository by using this git repo:

To make his repo work with ROS2 Foxy, you will need to make a small change in the CMakeLists.txt file. Go to line 26 in that file and delete the apriltag:: token in the AprilTagNode apriltag::apriltag part.

Next, you'll want to save that file and run colcon build in the apriltag_ros folder. Once it is done building, you'll want to source the install/setup.bash file. Add this line to your .bashrc:

Creating a new package to concatenate camera information to each camera frame

In order to make the apriltag_ros node work, we need to make sure that camera info messages are being sent in sync with each camera frame published by the cam2image node. We have written an example node that does just that. You can download it here:

You will need to replace the matrices in the node file to match your camera calibration parameters. The source file is located at pypysub/py_pysub/publisher_member_function.py. Once you have done that, make sure to build and install the node and source the install/setup.bash file.

Running the code

To run the code, you'll need to run the following ROS nodes:

FastRTPS and the microRTPS Agent

FastRTPS and the microRTPS agent are needed on NavQ in order to bridge uORB topics from PX4 to ROS2 on NavQ over a UART or UDP connection. Follow the guide below to build and install these packages.

Follow the link below for more details on microRTPS and PX4 ROS Com:

Installing FastRTPS and PX4 ROS Com on NavQ

Prerequisites

FastRTPS installation

First, we will install the FastRTPS project from eProsima. Use the following commands below to do so:

px4_ros_com installation

Next, we will build and install the necessary software that will allow us to use ROS2 to communicate with the microRTPS bridge. First, run the following commands:

Run the following commands to enable a 1GB swapfile:

Now, build the workspace:

Sourcing ROS2 bash files

In order to run all of your specific ROS2 software successfully, you must source the install/setup.bash files in each of your ROS2 workspace folders. Add the following lines to your .bashrc to do so:

Next steps

Continue to the next page to set up a systemd service that will automatically start the micrortps agent on your NavQ. The guide will also cover how to automatically start the client on the FMU.

ROS2 Foxy Fitzroy Install Guide

Follow the guide at the link below to install ROS2 Foxy Fitzroy on your NavQ running the Demo image.