ROS2—Thymio-II interaction

This repository contains some information to use the Thymio-II robot with ROS2. The procedure have been tested on a Arch Linux distribution and seems to work both for cable-connected and dongle-connected robots. Unfortunately, the procedure does not seems to work under MacOS due to the impossibility of accessing the port from inside a container.

This readme file is organized as follows:

1. Setup steps
2. PC—Thymio-II interaction
3. Troubleshoot

1. Install Docker:

$ sudo pacman -S docker
$ sudo systemctl start docker
$ sudo systemctl enable docker
$ sudo usermod -aG docker $USER # add your user to the docker group to run Docker commands without sudo

2. Build the docker image:

$ docker buildx build --no-cache --debug -t pbaldini/ros-aseba:lyrical .

3. Start the docker container with access to the connected devices:

$ docker run \                      # start a new container
    --rm \                          # the container is removed after termination
    -it \                           # start the container in interactive mode
    --privileged \                  # the container has access to all the devices connected to the system (potential vulnerability issue)
    -v `pwd`:/ros_ws/src \          # show the current directory in the container at the specified path
    --workdir /ros_ws/src \         # set the work directory insider the container as the mirror of this launch directory
    pbaldini/ros-aseba:lyrical \    # launch the ros-aseba foxy image
    bash                            # use the bash terminal as entrypoint

4. Install your code package to be launched by ROS2:

$ colcon build --merge-install
$ source install/setup.sh

5. Launch your ROS2 package:

$ ros2 launch PACKAGE_NAME FILE_NAME.launch

You can control the Thymio-II directly from the PC by using ROS2. You can find some examples on how to do it via cli at this link, and on how to do it programmatically in the example folder. In any case, the first step will be to open another shell in the container:

$ docker exec -it CONTAINER_NAME bash
$ source install/setup.sh

You can now interact with the node, for example by running:

$ ros2 topic echo /node_51214/aseba/description
$ ros2 topic pub -r 1 /node_51214/aseba/events/message asebaros_msgs/Event '{data:  [100]}'

• If asebaros returns the error Connection failed (0) check that the Thymio-II is turned on.
• If asebaros returns the error Connection failed (13) you probably don't have the rights to used the device; in this case, you can run the following command sudo chmod 777 /dev/ttyACM0 (note that the device name may differ).
• If specifying the name of the robot (i.e., device:="ser:name=Thymio-II") does not permit finding the device, you can try to specify directly the path with device:="ser:device=/dev/ttyACM0".
• If the robot behavior differs from what you code, ensure that the path variable in the .launch file points to the correct script.
• Using device:="ser:name=Thymio-II" seems to work also when using the USB dongle; nevertheless, in case of error you could try to use also device:="ser:name=Thymio-II Wireless".