(Jetson Project2#2)_RPLidar A1_setup

Part 3: Configuring RPLidar A1 with Modified Launch File

In this section, we'll set up the RPLidar A1 on your Jetson Nano B01. We'll clone the rplidar_ros package, modify the launch file as per your requirements, and ensure that the RPLidar is correctly interfaced with ROS Noetic.
Step 1: Clone the rplidar_ros Repository

First, navigate to your Catkin workspace's src directory and clone the rplidar_ros repository from GitHub.

cd ~/catkin_ws/src
git clone https://github.com/Slamtec/rplidar_ros.git

Step 2: Build the rplidar_ros Package

After cloning the repository, navigate back to the root of your Catkin workspace and build the workspace to compile the newly added package.

cd ~/catkin_ws
catkin_make

Once the build process is complete, source the workspace to ensure that ROS recognizes the new package.

source devel/setup.bash

Step 3: Verify RPLidar A1 Detection

Before proceeding, ensure that your RPLidar A1 is connected to your Jetson Nano and is recognized by the system.

Connect the RPLidar A1 to the Jetson Nano via USB.

Identify the Serial Port:

Use the following command to list the connected USB devices and identify the RPLidar's serial port (commonly /dev/ttyUSB0).

ls /dev/ttyUSB*

If you don't see /dev/ttyUSB0, you might need to check the connection or use dmesg | grep tty to find the correct port.

Step 4: Create a Custom Launch File (rplidar_a1.launch)

Instead of using the default rplidar.launch, we'll create a custom launch file named rplidar_a1.launch to accommodate any specific configurations for the A1 model.

Navigate to the rplidar_ros Launch Directory:

cd ~/catkin_ws/src/rplidar_ros/launch

Create the rplidar_a1.launch File:

touch rplidar_a1.launch

Edit the rplidar_a1.launch File:

Open the file with your preferred text editor (e.g., nano).

nano rplidar_a1.launch

Add the Following Content to rplidar_a1.launch:

<launch>
    <!-- Launch RPLidar Node -->
    <node name="rplidar_node" pkg="rplidar_ros" type="rplidarNode" output="screen">
        <!-- Replace '/dev/ttyUSB0' with your RPLidar's serial port if different -->
        <param name="serial_port" type="string" value="/dev/ttyUSB0"/>
        <!-- Set the baudrate for RPLidar A1 -->
        <param name="serial_baudrate" type="int" value="115200"/>
        <!-- Frame ID for the laser scan data -->
        <param name="frame_id" type="string" value="laser_frame"/>
        <!-- Invert the laser scan if necessary -->
        <param name="inverted" type="bool" value="false"/>
        <!-- Enable angle compensation -->
        <param name="angle_compensate" type="bool" value="true"/>
    </node>
</launch>

    Note: If your RPLidar A1 is connected to a different serial port (e.g., /dev/ttyUSB1), update the serial_port parameter accordingly.

Save and Exit:
    If using nano, press Ctrl + O to save and Ctrl + X to exit.

Step 5: Modify Permissions (If Necessary)

Ensure that your user has the necessary permissions to access the serial port.

Add Your User to the dialout Group:

sudo usermod -aG dialout $USER

Reboot Your System:

For the changes to take effect, reboot your Jetson Nano.

sudo reboot

Step 6: Launch the RPLidar A1 Node

After rebooting, you can launch the RPLidar A1 node using your custom launch file.

roslaunch rplidar_ros rplidar_a1.launch

You should see output indicating that the RPLidar node has started and is publishing laser scan data.
Step 7: Verify Laser Scan Data

To ensure that the RPLidar is functioning correctly, you can visualize the laser scan data using RViz or echo the /scan topic.

Using RViz:

Open a new terminal and launch RViz.

rviz

In RViz, set the Fixed Frame to laser_frame (as specified in the launch file).
Add a LaserScan display and set its Topic to /scan.

You should see the laser scan data being visualized in RViz.

Using rostopic:

Alternatively, you can echo the /scan topic to see raw data.

rostopic echo /scan

You should observe streaming data from the RPLidar.

Step 8: Troubleshooting Tips

Check if roslaunch is Installed

Ensure that roslaunch is installed in your ROS Noetic setup.

Check if roslaunch is installed:

which roslaunch

This should return something like /opt/ros/noetic/bin/roslaunch. If it doesn't, ROS Noetic might not have been properly installed, or there may be an issue with your environment variables.

If roslaunch is not found, you may need to reinstall ROS Noetic:

Run the following to reinstall ROS Noetic:

sudo apt install --reinstall ros-noetic-roslaunch

Step 3: Verify ROS Environment

Ensure that your environment is correctly set up for ROS. You can check the environment variables to verify this:

echo $ROS_DISTRO

This should return noetic. If it returns nothing or a different value, it means the environment isn't correctly set up.
Step 4: Verify Workspace Setup

Go to the root of your Catkin workspace:

cd ~/catkin_ws

Check that the workspace is built properly:

catkin_make

Source the workspace again after building:

source ~/catkin_ws/devel/setup.bash

Step 5: Try Running roslaunch Again

After sourcing the environment and ensuring the workspace is properly built, try running your launch file again:

roslaunch rplidar_ros rplidar_a1.launch

No Data Received:
    Ensure that the RPLidar is properly connected.
    Verify the serial port in the launch file.
    Check if the RPLidar is powered on.

Permission Denied Errors:
    Make sure your user is added to the dialout group.
    Reboot after modifying group memberships.

Incorrect Frame ID:
    Ensure that the frame_id in the launch file matches the one used in your robot's TF tree.