Lab1: Rampup and ROS

Lab1: Rampup and ROS
CSCI 545

1 Intro
In this lab, you will be setting up your system and getting acquainted with ROS. This lab is very
important since it will setup the base on top of which you will work for subsequent labs. You will
need to submit a lab report (pdf) and two python files (for the publisher/subscriber exercise).
Submission format: Your submission should be on your group’s github repo. Create a folder
called Lab1. Files should be placed in that folder like this:
Lab1/report.pdf
Lab1/code/<files>
2 Working with your project repository
1. First, clone your repo for the class
git clone https://github.com/usc-csci-545-fall-2021/<your-repo>.git
cd <your-repo>
2. Make your changes for the lab as necessary
3. (If you haven’t already,) commit all your changes
git add <files to add>
git commit -m <Your commit message>
4. Push your changes to the repo (we will only look at the master branch)
git push origin master
3 Pre-requisites for this tutorial
• Your VM or native install should have ROS-kinetic installed setup with no catkin workspace
(you create one yourself)
4 Verify ROS Install
1. Create a catkin workspace
mkdir -p ~/catkin_ws/src
cd ~/catkin_ws
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catkin build
source ~/catkin_ws/devel/setup.bash
Permanently add to path
echo ’source ~/catkin_ws/devel/setup.bash’ >> ~/.bashrc
2. Check environment variables
printenv | grep ROS
Check if ROS_ROOT, ROS_PACKAGE_PATH, etc. are setup. If not, run
source /opt/ros/kinetic/setup.bash
and then
source ~/catkin_ws/devel/setup.bash
For a permanent solution, you should add these lines to your ~/.bashrc
echo ‘source /opt/ros/kinetic/setup.bash‘ >>~/.bashrc
echo ‘source ~/catkin_ws/devel/setup.bash‘ >>~/.bashrc
3. You should be able to see which ROS packages are installed. rospack list You can see
where a package is installed with rospack find <package>
5 Create your own package
The simplest possible package might have a structure which looks like this:
my_package/
CMakeLists.txt
package.xml
1. cd ~/catkin_ws/src
2. catkin_create_pkg cs545_lab1 std_msgs rospy roscpp
This creates a package named cs545_lab1 that lists std_msgs, rospy, and roscpp as dependencies
3. Build your catkin workspace cd ~/catkin_ws/
catkin build
4. After build succeeds source ~/catkin_ws/devel/setup.bash
5. Verify that your package has installed
rospack list | grep cs545
Should return the name of your package
If you ever need to change dependencies for you package, you would have to edit the package.xml and CMakeLists.txt. See this tutorial page for more info.
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6 ROS exercises
Note: You will need multiple terminals for this section. Consider using programs to handle this
use-case, such as tmux or Terminator.
1. Run turtlesim
(a) Terminal1: roscore
(b) Terminal2: rosrun turtlesim turtlesim_node
(c) Terminal3: rosrun turtlesim turtle_teleop_key
(d) Select Terminal3 and then use the arrow keys to move the turtlebot
2. Find topics using rostopics
(a) Get list of topics with rostopic list
(b) Run rqt_graph to see a graphical representation of the nodes. Explain what you see
in 1-3 sentences.
(c) Get some info from a rostopic.
3. Record data using rosbag record
(a) Terminal4: mkdir /tmp/bagfiles # gets cleared on reboot
(b) cd /tmp/bagfiles
(c) rosbag record -O baggy -a
(d) Move turtlebot using arrow keys in Terminal3
(e) After recording for a few seconds, kill (Ctrl-C) the rosbag record in Terminal4
4. Play it back using rosbag play
(a) Kill (Ctrl-C) the turtle teleop key in Terminal3
(b) cd /tmp/bagfiles
(c) rosbag info baggy.bag
(d) rosbag play baggy.bag
5. Explain in 3-5 sentences the difference between rosservice, rostopic, rosparams, and rosbag.
7 Publisher and Subscriber Topics
This section requires you to write code to create a publisher and subscriber for a topic. Refer to
the ROS tutorial slides presented in class or the official ROS tutorials for more information on this.
You may need to use multiple terminals.
1. Write a publisher, using the skeleton code provided in publisher_exercise.py
2. Move the file to ~/catkin_ws/src/cs545_lab1/scripts/
3. catkin build cs545_lab1
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4. Make the publisher executable
chmod +x ~/catkin_ws/src/cs545_lab1/scripts/publisher_exercise.py
5. Run roscore to start ROS
6. Run your publisher: rosrun cs545_lab1 publisher_exercise.py
7. Verify that the topic is being published using rostopic list and rostopic echo
8. Write a subscriber, using the skeleton code provided in subscriber_exercise.py
9. Do the necessary steps to build and run the subscriber. Make sure you are able to receive the
message and are printing it out.
8 Report
Write a report comprising of all the textual answers required in this lab. The report should be in
.pdf format.
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