turtlebot_launcher

ROS2 service to launch ping pong ball using flywheel-based launcher. Meant for Turtlebot3 platform.

Written for NUS CDE2310 AY24/25.

Dependencies:

• RPi.GPIO
• rclpy
• std_srvs

Installation:

1. Navigate to source folder within your workspace. (In this case, 2310_workspace.)

cd ~/2310_workspace/src

2. Git clone repository into folder

git clone https://github.com/cde2310grp6/turtlebot_launcher.git

3. Navigate back to workspace and build using colcon

cd ~/2310_workspace
colcon build --packages-select turtlebot_launcher

Running the service:

ros2 run turtlebot_launcher launcher_service 

Calling the service through cmd line

For debugging purposes, it may be useful to be able to call the service via command line
Ensure the above service is running, afterwards in another terminal:

ros2 service call /launch_ball std_srvs/srv/Trigger "{}"

Calling the service through another node

Include this in the init of the node:

self.launcher_service = self.create_client(Trigger, 'launch_ball')

Sample service call and callback functions within node:

 def launch_now(self):
     self.get_logger().info("calling launcher")
     self.req = Trigger.Request()
     # Ensure service is available
     if not self.launcher_service.wait_for_service(timeout_sec=5.0):
         self.get_logger().warning('launcher service not available')
         return
     # Call the service asynchronously and handle the response when ready
     future = self.launcher_service.call_async(self.req)
     future.add_done_callback(self.launch_callback)

 def launch_callback(self, future):
     try:
         response = future.result()  # Get the response from the service call
         # Update saving_in_progress to continue saving the next target
         self.saving_in_progress = False
     except Exception as e:
         self.get_logger().error(f"launch service call failed: {e}")

Updating:

Enter the turtlebot_launcher folder and git pull, then build with colcon

cd ~/2310_workspace/src/turtlebot_launcher && git pull
cd ~/2310_workspace && colcon build --packages-select turtlebot_launcher