Jetbot ROS

Linux Version

JetPack 4.5.1 / Ubuntu 18.04

Use: jetson-nx-jp451-sd-card-image

Note: the process below will likely exceed the disk capacity of a 16GB filesystem,so a larger SD card should be used. ( Advice more than 64GB )

Install ROS

Install ROS melodic

# enable all Ubuntu packages:
$ sudo apt-add-repository universe
$ sudo apt-add-repository multiverse
$ sudo apt-add-repository restricted

# add ROS repository to apt sources
$ 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

# install ROS Base
$ sudo apt-get update
$ sudo apt-get install ros-melodic-ros-base

# add ROS paths to environment
$ sudo sh -c 'echo "source /opt/ros/melodic/setup.bash" >> ~/.bashrc'

Close and restart the terminal.

Install python and adafruit libraries

# pip should be installed
$ sudo apt-get install python-pip

# install Adafruit libraries
$ pip install Adafruit-MotorHAT
$ pip install Adafruit-SSD1306

Add i2c too user

$ sudo usermod -aG i2c $USER

Create the catkin workspace

Create a ROS Catkin workspace to contain our ROS packages.

# create the catkin workspace
$ mkdir -p ~/workspace/catkin_ws/src
$ cd ~/workspace/catkin_ws
$ catkin_make

# add catkin_ws path to bashrc
$ sudo sh -c 'echo "source ~/workspace/catkin_ws/devel/setup.bash" >> ~/.bashrc'

Close and open a new terminal window. Verify that your catkin_ws is visible to ROS.

$ echo $ROS_PACKAGE_PATH 
/home/nvidia/workspace/catkin_ws/src:/opt/ros/melodic/share

Install Jetbot_ros

Clone and build the jetbot_ros repo.

# git and cmake should be installed
$ sudo apt-get install git cmake

# clone the repo
$ cd ~/workspace/catkin_ws/src
$ git clone https://github.com/waveshare/jetbot_ros

# build the package
$ cd ../    # cd ~/workspace/catkin_ws
$ catkin_make

# confirm that jetbot_ros package can be found
$ rospack find jetbot_ros
/home/nvidia/workspace/catkin_ws/src/jetbot_ros

Test Jetbot

Running the ROS master

Next, let's check that the different components of the robot are working under ROS.

First open a new terminal, and start roscore.

$ roscore

Roscore

Running the Motors

Open a new terminal, and start the jetbot_motors node.

$ rosrun jetbot_ros jetbot_motors.py

Open a new terminal, and check jetbot_motors node is open.

$ rosnode list
$ rostopic list

Rosnode list

Using the Debug OLED

If you have an SSD1306 debug OLED on your JetBot, you can run the jetbot_oled node to display system information and user-defined text.

$ rosrun jetbot_ros jetbot_oled.py

By default, jetbot_oled will refresh the display every second with the latest memory usage, disk space, and IP addresses.

OLED print

Use the keyboard to control jetbot movement

Open a new terminal to run teleop_key node.After the program is running, input W, S, D, A four keys on the keyboard to control the jetbot to move forward, backward, right, and left.

$ rosrun jetbot_ros teleop_key.py

Can see the running action from the jetbot_motors node terminal.

Motors node

Create lidar scan node

Let’s create a package.

$ cd ~/catkin_ws/src
$ catkin_create_pkg laser_values rospy
$ cd laser_values
$ mkdir launch

Add a python script under src with the following code.

import rospy
from sensor_msgs.msg import LaserScan

def callback(msg):
    print len(msg.ranges)

def callback(msg):
    # values at 0 degree
    print msg.ranges[0]

rospy.init_node('scan_values')
sub = rospy.Subscriber('/scan', LaserScan, callback)
rospy.spin()

Then create a launch file under lunch directory to launch the script.

<launch>
    <node pkg="laser_values" type="scan.py" name="scan_values" output="screen">
        
    </node>
</launch>

First open a new terminal, and start roscore.

$ roscore

Open a new terminal, and start the laser.launch node.

$ roslaunch laser_values laser.launch

Install rviz

Install rviz by entering the following commands in the terminal.

$ sudo apt update
$ sudo apt install rviz

First open a new terminal, and start roscore.

$ roscore

Open a new terminal, and start the rviz node.

$ rosrun rviz rviz

RP Lidar install

First install rplidar sdk.

$ cd rplidar_sdk_vX.X.X/sdk/sdk/
$ make
$ ls /dev/ttyUSB*