A simple first node program in ROS. Uses Python and the DIS Python implementation to send DIS updates whenever a GPS fix is received and published on the topic. To run, in Ubuntu with ROS Kinetic installed: 0. Make sure the ROS config file is sourced. It's a good idea to put this in your ~/.bashrc: # ROS environment source /opt/ros/kinetic/setup.bash This specifies the kinetic kame release. There may be other releases installed under /opt/ros. 1. Run roscore in a terminal window: roscore This starts up the messaging infrastructure that allows topics to be published and received. 2. In another terminal window, start a node that simulates sending GPS fixes. ROS has a standard topic for publishing GPS fixes, and this simulates a sensor providing these fixes. First, source the module setup.bash cd first source devel/setup.bash Then start the ROS node that simulates a GPS sensor publishing position fixes to the standard topic for GPS position fixes: rosrun dis gps_sensor_sim.py This uses the module "dis" (in the src directory) and runs the node gps_sensor_sim.py (in the src/dis/scripts directory). 3. Likewise, start up a node that will receive the GPS position updates and publish DIS updates: cd first source devel/setup.bash rosrun dis dis_sender.py This will start receiving simulated GPS position fixes on the standard ROS topic and send DIS entity state PDUs that reflext the position of the robot. You should change the code in first/src/dis/scripts/dis_sender.py to reflect the correct bcast address, port, and entity state PDU settings, such as the entity type. 4. Visualize the node structure. ROS uses cooperating processes that communicate via topics. You can see these processes ("nodes") and the topics that connect them by running rqt_graph: rqt_graph This will show the gps_sensor_sim node (started in step 2) publishing to the sensor_msgs/NavSatFix topic, and the dis_sender node receiving the messages from the sensor_msgs/NavSatFix topic. Automating Launch Since ROS robots often require many nodes to be started up, as with the multi-step rosrun commands above, the entire process can be automated via the roslaunch command. This uses the xml file named dis.launch to automate launching several nodes. Start roscore in a terminal window: roscore Then open another window and source the package setup.bash file cd first source devel/setup.bash and then launch the nodes: roslaunch dis.launch And then visualize the node structure with rqt_graph: rqt_graph
mcgredonps/first
First Robot Operating System (ros) project. Sends DIS packets after receiving updates from GPS. Uses python.
PythonBSD-2-Clause