3. ROS Workspace Setup

Equipment Required:

  • Fully built F1TENTH vehicle

  • Pit/Host computer OR

  • External monitor/display, HDMI cable, keyboard, mouse

Approximate Time Investment: 1.5 hour

Overview

We use ROS to connect everything together and ultimately run the car. We’ll need to set up the ROS workspace, set up some udev rules, and test the lidar connection. Everything in this section is done on the Jetson NX so you will need to connect to it via SSH from the Pit laptop or plug in the monitor, keyboard, and mouse.

1. Setting Up the ROS Workspace

Connect to the Jetson NX either via SSH on the Pit laptop or a wired connection (monitor, keyboard, mouse).

On the Jetson NX, setup your ROS workspace (for the driver nodes onboard the vehicle) by opening a terminal window and following these steps.

  1. Clone the following repository into a folder on your computer.

    $​ ​cd​ ~/sandbox (or whatever folder you want to work ​in​)
$​ git ​clone​ https://github.com/f1tenth/f1tenth_system

  2. Create a workspace folder if you haven’t already, here called f1tenth_ws, and copy the f1tenth_system folder into it.

    $​ mkdir -p f1tenth_ws/src
$​ cp -r f1tenth_system f1tenth_ws/src/

  3. You might need to install some additional ROS packages.

    For ROS Kinetic:

    $​ sudo apt-get update
$​ sudo apt-get install ros-kinetic-driver-base

    For ROS Melodic:

    $​ sudo apt-get update
$​ sudo apt-get install ros-melodic-driver-base

  4. Make all the Python scripts executable.

    $​ ​cd​ f1tenth_ws
$​ find . -name “*.py” -exec chmod +x {} \;

  5. Move to your workspace folder and compile the code (catkin_make does more than code compilation - see online reference).

    $​ catkin_make

  6. Finally, source your working directory into your shell using

    $​ source devel/setup.bash

Congratulations! Your onboard driver workspace is all set up.

2. Udev Rules Setup

When you connect the VESC and a USB lidar to the Jetson, the operating system will assign them device names of the form /dev/ttyACMx, where x is a number that depends on the order in which they were plugged in. For example, if you plug in the lidar before you plug in the VESC, the lidar will be assigned the name /dev/ttyACM0​, and the VESC will be assigned /dev/ttyACM1​. This is a problem, as the car’s ROS configuration scripts need to know which device names the lidar and VESC are assigned, and these can vary every time we reboot the Jetson, depending on the order in which the devices are initialized.

Fortunately, Linux has a utility named ​udev​ that allows us to assign each device a “virtual” name based on its vendor and product IDs. For example, if we plug a USB device in and its vendor ID matches the ID for Hokuyo laser scanners (15d1), ​udev​ could assign the device the name /dev/sensors/hokuyo instead of the more generic /dev/ttyACMx​. This allows our configuration scripts to refer to things like /dev/sensors/hokuyo and /dev/sensors/vesc​, which do not depend on the order in which the devices were initialized. We will use udev to assign persistent device names to the lidar, VESC, and joypad by creating three configuration files (“rules”) in the directory /etc/udev/rules.d.

First, as root, open /etc/udev/rules.d/99-hokuyo.rules in a text editor to create a new rules file for the Hokuyo. Copy the following rule exactly as it appears below and save it:

KERNEL=="ttyACM[0-9]*", ACTION=="add", ATTRS{idVendor}=="15d1", MODE="0666", GROUP="dialout", SYMLINK+="sensors/hokuyo"

Next, open /etc/udev/rules.d/99-vesc.rules and copy in the following rule for the VESC:

KERNEL=="ttyACM[0-9]*", ACTION=="add", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="5740", MODE="0666", GROUP="dialout", SYMLINK+="sensors/vesc"

Then open /etc/udev/rules.d/99-joypad-f710.rules and add this rule for the joypad:

KERNEL=="js[0-9]*", ACTION=="add", ATTRS{idVendor}=="046d", ATTRS{idProduct}=="c219", SYMLINK+="input/joypad-f710"

Finally, trigger (activate) the rules by running

$ sudo ​udevadm control --reload-rules
$ sudo udevadm trigger​

Reboot your system, and you should find three new devices by running

$ ls /dev/sensors
$ hokuyo​    vesc

and:

$ ls /dev/input
$ joypad-f710​

If you want to add additional devices and don’t know their vendor or product IDs, you can use the command

$ sudo ​udevadm info --name=<your_device_name> --attribute-walk

making sure to replace <your_device_name> with the name of your device (e.g. ttyACM0 if that’s what the OS assigned it. The Unix utility ​dmesg​ can help you find that). The topmost entry will be the entry for your device; lower entries are for the device’s parents.

3. Testing the Lidar

This section assumes that the lidar has already been plugged in (either to the USB hub or to the Orbitty’s ethernet port). If you are using the Hokuyo 10LX or a lidar that is connected via the ethernet port of the Orbitty, make sure that you have completed the Hokuyo 10LX Ethernet Connection section before preceding.

Once you’ve set up the lidar, you can test it using ​urg_node​/hokuyo_node (replace the hokuyo_node by the urg_node if you have 10LX with Ethernet connection: https://github.com/ros-drivers/urg_node.git), ​rviz​, and ​rostopic​.

  1. If you’re using the 10LX:

    • Start roscore​ in a terminal window.

    • In another (new) terminal window, run rosrun urg_node urg_node _ip_address:="192.168.0.10"​. Make sure to supply the urg node with the correct port number for the 10LX.

    • This tells ROS to start reading from the lidar and publishing on the ​/scan​ topic. If you get an error saying that there is an “error connecting to Hokuyo,” double check that the Hokuyo is physically plugged into a USB port. You can use the terminal command lsusb​to check whether Linux successfully detected your lidar. If the node started and is publishing correctly, you should be able to use rostopic echo /scan​ to see live lidar data.

    • In the racecar config folder under lidar_node set the following parameter in sensors.yaml: ip_address: 192.168.0.10. In addition in the sensors.launch.xml change the argument for the lidar launch from hokuyo_node to urg_node do the same thing for the node_type parameter.

  2. If you’re using the 30LX:

    • Run roslaunch racecar teleop.launch in a sourced terminal window, by default, the launch file brings up the hokuyo node.

Once your lidar driver node is running, open another terminal and run rosrun rviz rviz​ or simply rviz to visually see the data. When rviz​ opens, click the “Add” button at the lower left corner. A dialog will pop up; from here, click the By topic tab, highlight the LaserScan topic, and click OK. You might have to switch from viewing in the \map frame to the laser frame. If the laser frame is not there, you can type in laser in the frame text field.

rviz will now show a collection of points of the lidar data in the gray grid in the center of the screen. You might have to change the size and color of the points in the LaserScan setting to see the points clearer.

  • Try moving a flat object, such as a book, in front of the lidar and to its sides. You should see a corresponding flat line of points on the ​rviz​ grid.

  • Try picking the car up and moving it around, and note how the lidar scan data changes,

You can also see the lidar data in text form by using ​``rostopic echo /scan`` ​. The type of message published to it is sensor_msgs/LaserScan​, which you can also see by running rostopic info /scan​ . There are many fields in this message type, but for our course, the most important one is ​ranges​, which is a list of distances the sensor records in order as it sweeps from its rightmost position to its leftmost position.

With all of the parts connected now, we can move on to driving with a joystick!

getting_started/firmware/img/drive01.gif