ROS

When using the Robot Operating System (ROS), it’s fairly common to want to shut down a launched system if a specific node (or set of nodes) exits. This is pretty easy in ROS1, because launch files support the required attribute on each node. As a result, crafting a two-node system where one of the nodes is required is straightforward: <launch> <node name = "talker" pkg = "talker" type = "talker_node" /> <node name = "listener" pkg = "listener" type = "talker_node" required = "true" /> </launch> This launch file creates a talker/listener system where, if the talker exits the system continues trucking along, but if the listener exits the entire launched system is shut down....

The snapcraft CLI has supported building ROS1 snaps for a while via the catkin plugin. We supported the ROS2 betas via the ament plugin, but that was before Open Robotics had a ROS 2 package repository setup, which meant that the ament plugin built the ROS 2 underlay from source, and it was predictably dreadfully slow. However, the stable releases of ROS2 introduced a new build system called colcon, and also had their own package repositories setup....

Snaps bundle their dependencies, which take time to fetch and unpack, and they’re typically made up of multiple parts, each of which need to be built and installed into the snap. Once you finish this process, you need to install the snap and test it out. Once you notice that your code is terrible and doesn’t work the way you thought, you have to make a change and go back through that process again....

Part of the snapcraft CLI’s development roadmap this cycle includes the ability to build snaps on distros other than Ubuntu. Part of that work includes investigating each plugin to determine if it’s possible to get it working on other distros. As a result, I’ve been looking into the Catkin plugin recently, using Fedora 27 as my proving ground (since that’s the distro with which I’m most familiar after Ubuntu). The first thing you’ll notice trying to get ROS working on Fedora is that, unlike Ubuntu, where Open Robotics maintains infrastructure hosting a repository of Debian packages, there is no repository for you to use: you must build ROS from source....

UPDATE: I’m leaving this series up for historical purposes, but please note that I no longer recommend Ubuntu Core or snaps for use in robotics. This is the fifth (and final) blog post in this series about creating your first robot with ROS and Ubuntu Core. In the previous post we discussed methods of control, did a little math, and wrote the ROS driver for our robot. But it still required several nodes to be running at once, and sharing it with the world involved uploading your source code somewhere and convincing people to install ROS, build your package, and use it....