Syskit bundles are first and foremost Roby applications. As such, the tools and methods to interact with a Roby application also apply to the ones that are using Syskit. You should therefore have first a look at what can be done with a Roby application. In particular, you should look at the Roby action interface and the ways one can interact with a running Roby application

What this page is going to be about is how Syskit fits inside these concepts: how profiles are mapped to Roby actions, and what it means to deploy subsystems through the action interface.

Using profiles as Roby actions

In fine, when using Syskit, one designs a “master” profile in which all the behaviours / needed subsystems are defined. This master profile can then be injected in an action interface class (usually the main interface in models/actions/main.rb) with

class Main < Roby::Actions::Interface
  use_profile MyProject::MyMasterProfile
end

This defines actions for all definitions and devices this profile defines. The definitions are suffixed with _def and the devices with _dev.

Deploying subsystems through the action interface

Since definitions and devices are now actions, they can be used normally in the action interface. One can therefore start a device (for instance for a small data gathering session) on the command line with:

roby run -rmyrobot left_camera_dev!

Alternatively, the shell interface allows to start and stop specific subsystems using the action interface and job systems. Start a shell to connect to a running Syskit/Roby controller with

roby shell

and then:

left_camera_dev!
jobs
kill_job 1

Finally, one can add actions-as-missions in the code (for instance in the controller file to start some services “by default”) with

Robot.left_camera_dev!

What is important to understand at this point is that Syskit compute the merged network of all the required subsystems. I.e. if you start two big networks that share parts, these parts will actually be shared in the final component network, without any additional work from your part. This video tries to explain this process:

TODO: video

What happens if you try to start a new new subsystem that cannot be merged with the running network ? This happens for instance if the two networks are trying to use the same device in different configurations, or if they have incompatible frame transformation configurations When this happens, the newly started network will not be deployed, and the rest will stay the same. The error message will try to give you some insights as to why the deployment is not possible, but we have to admit that, right now, the explanation requires quite a bit of thinking on your part. This is something we try to improve in the long run.