Networking with ROS on RaspBerry PI 3B+

Images were transferred and streamed in video using ROS(Robot Operating System) over ethernet and wifi networks from RaspBerry Pi 3B+ to workstation for processing.

Steps to get networking done in your system

Dependencies

Install ROS Kinetic Link
Install ROS on Raspbian Link
Install OpenCV on your system as well as on RaspBerry Pi Link
Install cv_bridge
Install arp-scan on your system
Install openssh-server on your system as well as on RaspBerry Pi and enable ssh on both the systems

Now you are ready to use this repo

Clone the repo to your desired directory on your system

$ cd {Your directory}
$ git clone https://github.com/Shubham-Sahoo/Networking.git

Make a catkin workspace, if you already don't have it

$ mkdir -p ~/catkin_ws/src
$ cd catkin_ws/
$ catkin_make
$ cd catkin_ws/src/
$ catkin_create_pkg networking rospy roscpp std_msgs OpenCV cv_bridge image_transport

Now copy the publisher and subscriber file to your networking directory just created in catkin_ws/src

$ cd
$ cd {Your directory}/Networking/src
$ cp Publisher.cpp Subscriber.cpp /home/{user}/catkin_ws/src/networking/src/

Now change your CMakeLists.txt in networking folder by adding these lines at the end of the file

include_directories(${OpenCV_INCLUDE_DIRS})

add_executable(Publisher src/Publisher.cpp)
target_link_libraries(Publisher ${OpenCV_LIBRARIES} ${catkin_LIBRARIES})

add_executable(Subscriber src/Subscriber.cpp)
target_link_libraries(Subscriber ${OpenCV_LIBRARIES} ${catkin_LIBRARIES})

You can check the CMakeLists.txt for reference

Now make the package

$ cd ~/catkin_ws
$ catkin_make
$ source devel/setup.bash

Repeat the exact same process of using the repo on Raspberry Pi

Now you are ready for the networking part

Through Ethernet cable

Connect the Raspberry Pi to your System and do execute the following on terminal

sudo arp-scan --interface=eth0 --localnet

You will get a IP Address similar to 10.42.XX.XX
Copy the IP Address and use it to ssh into the RaspBerry Pi

sudo ssh pi@10.42.XX.XX

Now we have two choices:

Run roscore on RaspBerry Pi
Run roscore on OffBoard System

Let's take the first case where roscore is running on RaspBerry Pi

Open a terminal on RaspBerry Pi and do the following

export ROS_MASTER_URI=http://10.42.XX.XX(IP of Raspberry Pi):11311
export ROS_IP=10.42.XX.XX(IP of RaspBerry Pi)
roscore

In another terminal on RaspBerry Pi

export ROS_MASTER_URI=http://10.42.XX.XX(IP of Raspberry Pi):11311
export ROS_IP=10.42.XX.XX(IP of RaspBerry Pi)
rosrun networking Publisher

Now you need to setup your system to subscribe the messages

Open a terminal on your system and do

ifconfig

Note the IP Address of your system of the format 10.42.YY.YY

In the same terminal execute

export ROS_MASTER_URI=http://10.42.XX.XX(IP of Raspberry Pi):11311
export ROS_IP=10.42.YY.YY(IP of your system)
rosrun networking Subscriber

If everything goes well, a window will pop up showing the video from the camera of RaspBerry Pi

The second case can also be done just by reversing the operations of roscore on the machines.