The ROCK 4 SE’s Hexa core Arm processor makes it a strong candidate for robotic control systems and, paired with the LiDAR Module, gives your robot the capability to accurately sense nearby objects and provide positioning data for navigation in and around its environment.
In this project, we demonstrate how to interface the LiDAR Module to the ROCK 4. Following the 10 steps from this guide, you’ll learn how to natively build the Robot Operating System (ROS) project on the ROCK 4 SE SBC and set up the LiDAR module with its SDK to run tests that show what the ROCK / ROS / LiDAR combination is capable of, as a starting point for robotics projects.
This step-by-step guide is the perfect starting point for developing autonomous robots for smart agriculture, construction, logistics, automotive, pharmaceutical and many other industries. It’s a practical “know-how” tutorial showing you how to pare the ROCK 4 SE and the LiDAR HAT to design and develop various ROS robotics projects, including autonomous manufacturing robots, food delivery robots, agriculture drones, welding robots, painting robots, construction robots, industrial robotic arms, and many more!
Robot Operating System (ROS) is a free, open-source software that defines the components, interfaces and tools for building advanced robots. It can be built and installed on the ROCK 4 and is compatible with the LiDAR Modules and its SDK. We tested ROS Melodic with a ROCK 4 SE board running Debian Buster with a 5.10 Linux kernel.
All the software is natively built and runs on the ROCK. You can SSH in remotely or use the Debian Desktop to open terminal sessions and run the Rviz visualisation package built into ROS.
Download and flash the Buster 5.10 kernel release to a high-quality branded SD card like SanDisk Ultra 32GB:
Follow the setup instructions here to configure the system, bring it up to date and configure WiFi.
Tip: SSH into the ROCK from another PC, so you can cut and paste the commands.
Add the ROS sources to Apt.
sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'
sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654
sudo apt update
sudo apt install -y python2.7 python-rosdep python-rosinstall-generator python-wstool python-rosinstall build-essential cmake
sudo rosdep init && rosdep update
Ad Melodic desktop packages.
mkdir ~/ros_catkin_ws cd ~/ros_catkin_ws rosinstall_generator desktop --rosdistro melodic --deps --wet-only --tar > melodic-desktop-wet.rosinstall
wstool init -j8 src melodic-desktop-wet.rosinstall
Tip: If wstool init fails or is interrupted, you can resume the download by running this command:
wstool update -j4 -t src
cd ~/ros_catkin_ws rosdep install -y --from-paths src --ignore-src --rosdistro melodic -r --os=debian:buster
The installation should return with all dependencies if it was installed successfully.
This step builds and installs the ROS environment onto the ROCK’s OS. The terminal title updates with the progress showing the number of packages until completion – it takes about 120 mins to complete.
cd ~/ros_catkin_ws sudo ./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release --install-space /opt/ros/melodic -j2
Here we set up the ROS environment and run a test of the ROS installation by sending messages between 2 ROS nodes.
Roscore must be started first and left running. ROS Nodes publish and subscribe to messages, so a listener node is created to subscribe to the chatter topic, and a talker node is created that publishes messages on that topic.
echo source /opt/ros/melodic/setup.bash >> ~/.bashrc source ~/.bashrc
rosrun roscpp_tutorials listener
rosrun roscpp_tutorials talker
The screenshot below shows the messages being received by the listener node from the talker node.
Tip: C++ code for the listener and talker nodes can be found here:
ROS is now installed and working on the ROCK.
This step downloads and builds the LiDAR SDK for ROS. The package source code is available from the following repositories:
cd ~ mkdir -p ldLiDAR_ros_ws/src cd ~/ldLiDAR_ros_ws/src git clone https://github.com/ldrobotSensorTeam/ldLiDAR_stl_ros.git
git clone https://gitee.com/ldrobotSensorTeam/ldLiDAR_stl_ros.git
cd ~/ldLiDAR_ros_ws rosdep install -y --from-paths src --ignore-src --rosdistro melodic -r --os=debian:buster
cd ~/ldLiDAR_ros_ws catkin_make
The LiDAR SDK package is now installed.
Connect the LiDAR module to the ROCK using a USB-to-Serial module. Use a module with a 5V output to power the LiDAR and TX / RX signals operating at 3.3V (CMOS) logic levels. We used a CP2102 bridge from Waveshare.
Tip: Measure the voltage levels of your USB-toSerial bridge with a voltmeter by connecting it to the ROCK before connecting it to the LiDAR. Do not exceed the Max values in the table below.
With the ROCK powered on:
The LiDAR will start running – a scanning blue light should be visible through the top of the module.
Warning: Check the connectors before plugging in the USB connector.
|LiDAR Pin||USB-to-Serial Bridge||Colour||Min||Typical||Max|
|Pin 1 (TX)||RXD||White||0V||3.3V||3.5V|
|Pin 2 (PWM)||N/C||Yellow||0V||–||3.3V|
|Pin 3 (GND)||GND||Red||–||0V||–|
|Pin 4 (5V)||5V||Blue||4.5V||5V||5.5V|
Now that ROS, the LiDAR SDK and the module are connected, we can test that everything is working.
echo source ~/ldLiDAR_ros_ws/devel/setup.bash >> ~/.bashrc source ~/.bashrc
sudo chmod 777 /dev/ttyUSB0
roslaunch ldLiDAR_stl_ros ld06.launch
The scan topic should be listed.
rostopic echo /scan --noarr
You should see the output from the LiDAR module updating as it scans.
You must run this test on the ROCK desktop. It uses the Rviz visualisation package built into ROS to display the point cloud being streamed from the LiDAR sensor.
source ~/.bashrc roslaunch ldLiDAR_stl_ros viewer_ld06_kinetic_melodic.launch
You will see the data points mapped onto the 2D plane of Rviz.
We have shown how to set up and use the OKdo LiDAR Module with the ROCK 4 to add LiDAR obstacle detection and autonomous navigation capabilities to robotics projects based on ROS.
The ROCK’s powerful processing capabilities and ability to connect to various sensors make it a strong contender for controlling your next autonomous robot application!
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