Diffbot ROS Packages

The following describes the easiest way to make use of diffbot's ROS packages inside the ros-mobile-robots/diffbot repository.

The following steps will be performed on both, the workstation/development PC and the single board computer (SBC).

Development PC: use the dev container

On the development PC, the dev container does all of the following steps for you, in a Docker image with ROS Noetic, Gazebo and RViz. The steps below are still needed on the robot's SBC.

Git: clone diffbot repository

After setting up ROS on the SBC (Raspberry Pi 4B or Jetson Nano), install Git there, if git --version doesn't find it:

1	`sudo apt install git`

Then go to the workspace from ROS Setup, ~/catkin_ws, or create it, and clone the diffbot repository. It's public, so this needs no GitHub account:

mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/src
git clone https://github.com/ros-mobile-robots/diffbot.git

To use a released version instead of the latest code, clone a tag, for example the latest release, 1.1.0:

git clone --depth 1 --branch 1.1.0 https://github.com/ros-mobile-robots/diffbot.git

Push changes from the robot (optional)

Usually you change the code on your PC and pull it on the robot. To commit and push on the robot as well, set up your commit identity and authentication there as described in Git and GitHub. Authentication differs a little, because you work on the robot over SSH, without a browser:

HTTPSSSH

gh auth login on the robot shows a one-time code. Open https://github.com/login/device on your PC and enter it there. gh then stores a token on the robot, in a plain text file if no keyring is available; gh auth status shows where.

Instead of creating a key on the robot, let it use your PC's key through SSH agent forwarding. On your PC, in Linux or in the Ubuntu in WSL 2, load the key into the SSH agent, and connect with -A:

ssh-add ~/.ssh/id_ed25519
ssh -A your-user@192.168.0.20

If ssh-add can't connect to an agent, as in WSL 2, start one first with eval "$(ssh-agent -s)". On the robot, the clone needs the SSH address (see Git and GitHub, SSH tab).

The private key stays on your PC. But while you're connected, anyone with root access on the robot can use your agent to authenticate to GitHub as you. Forward it only to a robot you trust, such as your own (Using SSH agent forwarding).

Obtain (system) Dependencies

The diffbot repository relies on two sorts of dependencies:

Source (non binary) dependencies from other (git) repositories.
System dependencies available in the (ROS) Ubuntu package repositories. Also referred to as pre built binaries.

Source Dependencies

Let's first obtain source dependencies from other repositories. To do this the recommended tool to use is vcstool (see also https://github.com/dirk-thomas/vcstool for additional documentation and examples.).

Note

vcstool replaces wstool.

The diffbot repository has three .repos files that list these source dependencies. They clone into src/, so run vcs import from the root of the catkin workspace (~/catkin_ws) and pass in the file for the machine you're on:

Machine	Command	Clones
Development PC	`vcs import < src/diffbot/diffbot_dev.repos`	`rplidar_ros`, `remo_description`
Remo's SBC	`vcs import < src/diffbot/remo_robot.repos`	`rplidar_ros`, `remo_description`
DiffBot's SBC	`vcs import < src/diffbot/diffbot_robot.repos`	`rplidar_ros` (Slamtec), `raspicam_node`

vcs import reads the YAML file from stdin and clones every repository it lists.

Now that additional packages are inside the catkin workspace it is time to install the system dependencies.

System Dependencies

All the needed ROS system dependencies which are required by diffbot's packages can be installed using rosdep command, which was installed during the ROS setup. To install all system dependencies use the following command:

1	`rosdep install --from-paths src --ignore-src -y`

If rosdep can't resolve a dependency, it stops with an error that names it.

DiffBot: camera libraries first

DiffBot's camera driver, raspicam_node, needs the Raspberry Pi's camera libraries, which rosdep doesn't know. Add their rules as described on Raspberry Pi Camera before you run rosdep install.

Info

On the following packages pages it is explained that the dependencies of a ROS package are defined inside its package.xml.

After the installation of all dependencies finished (which can take a while), it is time to build the catkin workspace. Inside the workspace use catkin-tools to build the packages inside the src folder.

Note

The first time you run the following command, make sure to execute it inside your catkin workspace and not the src directory.

1	`catkin build`

Now source the catkin workspace either using the created alias or the full command for the bash shell:

1	`source devel/setup.bash`

On the robot, the next step is to flash the microcontroller, step 6 in Getting Started.

Examples

Now you are ready to follow the examples listed in the readme.

Info

TODO extend documentation with examples

Optional Infos

Manual Dependency Installation

To install a package from source clone (using git) or download the source files from where they are located (commonly hosted on GitHub) into the src folder of a ros catkin workspace and execute the catkin build command. Also make sure to source the workspace after building new packages with source devel/setup.bash.

cd ~/catkin_ws             # Navigate to the workspace
catkin build              # Build all the packages in the workspace
ls build                  # Show the resulting build space
ls devel                  # Show the resulting devel space

Note

Make sure to clone/download the source files suitable for the ROS distribution you are using. If the sources are not available for the distribution you are working with, it is worth to try building anyway. Chances are that the package you want to use is suitable for multiple ROS distros. For example if a package states in its docs, that it is only available for kinetic it is possible that it will work with a ROS noetic install.

Comments

Comments are GitHub Discussions, shown with giscus. Loading them connects to giscus.app (hosted by Vercel, USA) and GitHub (USA); you need a GitHub account to comment.