Interfacing with Systems

Create the interface between the logger and the equipment

Each cyber physical system (CPS) must have an interface to gather available data either in real time or post event to be stored using the RESPOND-R framework. Your next step is to find out what type of information is available and how it will be logged. It could be radiological readings over an rs232 interface or gps data over a web socket. If there is no way to get the data out you could just record the equipment using a webcam in which the interface is a video stream.

Once you have a general idea of what and how you and your confident that it can be incorporated go ahead and make a new package: http://www.ros.org/wiki/ROS/Tutorials/CreatingPackage. Be sure to include std_msgs, rospy, and roscpp.

Next you must define rosmsgs that represent the device. You may find that complex devices require multiple msgs due to multiple interfaces or different polling rates for different types of information. Check the creating messages tutorial for an explanation: http://www.ros.org/wiki/ROS/Tutorials/CreatingMsgAndSrv#Creating_a_msg

Below is an example of the GPS time returned over serial from the AirRobot sUAS. This is one of many messages representing the data available from the AirRobot.

#AirRobot example msg - gps_date_time.msg
Header header
string name
int32 flightTime
int32 day
int32 month
int32 year
int32 hour
int32 minute

Once you have defined all of your messages you should catkin_make to ensure everything went well. Next you need to create the connector between the systems raw data and ROS. This is broken up into 2 types, online and offline. Online is considered a real time data stream. The type will change which template you choose (if any). The goal is to convert the data from the system and publish to ROS using the msgs you created in the last step.

We have provided 3 templates to convert data. A real time template for gathering data over a socket, an offline template for converting CSV data, and a video template for capturing network streams. Take a look at each one and see if they will fit your situation. The Socket and the Video stream will usually be used together if you are interfacing with a teleoperated robot.

[Real Time Socket Template]
[Offline CSV Template]
[Video Stream Template]

On To [Creating a Startup file]