Is AllJoyn a good ROS alternative regarding message passing cross multiple devices?

Question

I've used ROS for a while, my environment is Raspberry Pi + Ubuntu + OpenCV + ROS + C/C++. I also use several ROS packages (tf2, usb_camera, slam related, and laser scanner capture.) Also, in my projects, nodes are in multiple devices, and I'm using multiple master package for one project.

I did review some tutorials about AllJoyn, but no handon experience so far.

The questions are:

1. regarding to message (especially, ROS image) passing cross devices, is AllJoyn a good ROS alternative? (devices are connected by wifi or bluetooth.)

2. For AllJoyn, does it still need single master (like roscore in ROS) to coordinate the nodes (or similar)?

Thanks.

Answer 1

I suppose if you really wanted it, you could - but it seems to be designed for smart home/building applications. I also suppose if you really wanted to, you could use ROS for a smart home too.

But I am not really seeing an advantage to AllJoyn over ROS, in terms of robotics. ROS is structured in an almost 'P2P network', any device can subscribe and publish topics. But AllJoyn seems to be more of a 'hub-and-spoke' network model, some devices listen, fewer think and talk.

For example, on an AllJoyn network, it seems that any device can publish its present state, but it is a central computer that is making the decisions and publishing those decisions. The whatever circuit is controlling that light bulb, or thermostat, is taking all of its directions from the computer running AllJoyn. There doesn't seem to be any leeway for 'independent thought' in the network. But in a ROS network, you do not need to use a 'central-anything'. I can have my nVidia Jetson (which is the piece actually running ROS) control an Arduino, which in-turn is controlling motors based on its own code. The Arduino is making decisions based on what its motors are doing, and what the Jetson is telling it to do, and the Jetson is making decisions based on what the Arduino is telling it and its motors are doing (among other pieces as well).

AllJoyn would be perfect if you wanted to do an IoT or smart home project with your RasPi, but it doesn't seem to make a lot of sense for robotics since it doesn't have a lot of flexibility when it comes to defining feedback into the network devices.

To answer your questions succinctly:

1. Probably not, not for robotics at least. But it would be good for an IoT project.
2. Yes. It sounds like it needs a 'master' even more so than ROS. The ROS master is mainly to keep track of what is actually on the network and what it is doing. AllJoyn's master is actually making all the decisions too (unlike ROS, where you write nodes for each item on the network, and those do the work).

Now I might be mistaken about AllJoyn's network structure, but this was my impression on it after reading up on it last night and this morning.