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cs:ros:tutorials:start [2016/09/09 17:30] James Irwin |
cs:ros:tutorials:start [2016/09/23 21:34] (current) Brandon Kallaher [ROS Tutorials] |
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| ===== ROS Tutorials ===== | ===== ROS Tutorials ===== | ||
| + | The [[ros>ROS/Tutorials|official ROS tutorials]] are very comprehensive, however I found the way they present ROS to a beginner results in a very steep learning curve. Here is our own set of tutorials, which are a work in progress. I may reference tutorials from other sites if I find them useful. | ||
| ==== Pre-requisites ==== | ==== Pre-requisites ==== | ||
| - | Basic linux command-line knowledge (specifically BASH) is assumed. If you are completely unfamiliar with the command line, go through the first few lessons on this: https://www.codecademy.com/learn/learn-the-command-line | + | Basic linux command-line knowledge (specifically BASH) is assumed. If you are completely unfamiliar with the command line, check out this[[https://www.codecademy.com/learn/learn-the-command-line|codecademy tutorial]], or [[https://www.youtube.com/playlist?list=PLII6oL6B7q78PKy6_R6JTkkYjVXZBZcVq | this series of videos]]. |
| + | |||
| + | ==== High Level Concepts ==== | ||
| + | ROS is many things, it is primarily a communication framework, but it also has a huge set of useful tools, including viewing data, navigating the filesystem, and starting up processes. | ||
| + | |||
| + | Each process is called a **node**. Nodes are designed to do a specific task. We can create complex functionality (such as controlling a robot) by building multiple nodes and having them talk together. | ||
| + | |||
| + | There are several ways for nodes to talk to each other, the most common one is a **topic**. The basic idea is that a single node can "publish" data to a topic, and then one or more nodes can "subscribe" to the topic and receive the data. | ||
| + | |||
| + | Nodes are typically grouped together into a **package**. All of our software is in a single package called "robosub". When you install ROS, several other packages are installed that provide some useful functionality, such as rqt_plot. | ||
| + | |||
| + | ==== Command Line Tools ==== | ||
| + | ROS provides many useful command-line tools. Your BASH environment gets access to these when you have the following line in your ~/.bashrc file: | ||
| + | <code bash> | ||
| + | source /opt/ros/indigo/setup.bash | ||
| + | </code> | ||
| + | Most ROS commands support tab autocompletion, so take advantage of it! | ||
| + | |||
| + | === Navigating the filesystem === | ||
| + | ROS has a few different commands that are useful for moving and looking around. They are typically in the form: | ||
| + | <code bash> | ||
| + | $ <command> <package_name> <...> | ||
| + | </code> | ||
| + | Most are based on the typical navigation functions: | ||
| + | * roscd | ||
| + | * rosls | ||
| + | |||
| + | === Starting nodes === | ||
| + | == Starting a single node == | ||
| + | While you can manually find the executable (or python script) and run it manually, ROS provides a tool for quickly finding and starting a node, the ''rosrun'' command: | ||
| + | <code bash> | ||
| + | $ rosrun <package_name> <node_name> | ||
| + | </code> | ||
| + | |||
| + | == Starting multiple nodes == | ||
| + | The ''roslaunch'' command allows you to launch multiple nodes at the same time. The nodes are specified in a special file called a launch file. | ||
| + | <code bash> | ||
| + | $ rosrun <package_name> <launchfile_name> | ||
| + | </code> | ||
| + | More information about launch files can be found [[|here]] | ||
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| + | |||
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| + | === Viewing active nodes and topics === | ||
| + | The ''rosnode'' command shows information about nodes. You can view all currently running nodes by running | ||
| + | <code bash> | ||
| + | $ rosnode list | ||
| + | </code> | ||
| + | |||
| + | Likewise, the ''rostopic'' command shows information about topics. You can view all currently active topics by running | ||
| + | <code bash> | ||
| + | $ rostopic list | ||
| + | </code> | ||
| + | |||
| + | |||
| + | === How to Write a ROS Node === | ||
| + | Check out these tutorials for whatever language you're using: [[ros>ROS/Tutorials/WritingPublisherSubscriber(c%2B%2B) | C++ ]] | ||
| + | [[ros>ROS/Tutorials/WritingPublisherSubscriber(python) | Python ]] | ||
