Networking

The TurtleBot 4 consists of two computing units: the Create® 3, and the Raspberry Pi. They connect to each other over a USB-C cable, which is used to both power the Raspberry Pi, and establish a ethernet connection between the units. Both units also have Wi-Fi cards. The Create® 3 is able to connect to only 2.4 GHz networks, while the Raspberry Pi can connect to both 2.4 and 5 GHz networks. The user can also use their PC to communicate with the robot over Wi-Fi.

DDS

ROS 2 has multiple DDS vendors, but the TurtleBot 4 only supports CycloneDDS and FastDDS out of the box. In Galactic, CycloneDDS is the default while in Humble, FastDDS is the default. The TurtleBot 4 can switch between the two DDS implementations on both versions of ROS 2.

Network Configurations

For ROS 2 networking, the TurtleBot 4 can function with two different configurations: Simple Discovery, and Discovery Server.

Simple Discovery

Simple Discovery is the default protocol that ROS 2 uses, and is available with both FastDDS and CycloneDDS. Simple Discovery uses multicasting to allow each ROS 2 participant to contact every other ROS 2 participant at the same time. This allows for all devices on the network to automatically discover each other's ROS 2 nodes.

To use the TurtleBot 4 in the multicast configuration, both the RPi4 and the Create® 3 should be connected to the same Wi-Fi network. It is recommended that the RPi4 is connected to a 5GHz network for improved performance, so the network must bridge the 2.4 GHz and 5 GHz bands. Networks that provide 2.4 GHz and 5 GHz on the same SSID may not work properly with the Create3. This issue can be avoided by using Discovery Server.

Note

Connecting the Raspberry Pi using a 2.4 GHz network or over a network with very limited bandwidth can limit functionality including navigation and sending/receiving images.

simple_discovery — TurtleBot 4 Simple Discovery configuration

Discovery Server

The Discovery Server option is supported only on FastDDS. The FastDDS Discovery Server allows for one or more devices on the network to act as a discovery server, while other devices are discovery clients for those servers. This is akin to the ROS Master in ROS 1. These discovery servers create connections between ROS 2 nodes to connect publishers and subscribers. Check out the Discovery Server documentation for more details.

Note

Multi-robot configuration with Discovery Server is not supported on Galactic.

With this configuration, the TurtleBot 4 is able to fully function without the Create® 3 being connected to Wi-Fi. Instead, all communication for each robot is routed through the Raspberry Pi which runs a discovery server.

Choosing a networking configuration

Each configuration has its own advantages and disadvantages.

Simple Discovery

Recommended for systems of up to 1-2 robots running simple functionality.

Advantages	Disadvantages
Easy to connect to the robot from any device on the network. The default discovery protocol in ROS 2, so there is no additional setup required. Supports both CycloneDDS and FastDDS.	Uses multicasting which can be problematic with some Wi-Fi networks, such as university and corporate networks. Create® 3 must also be connected to Wi-Fi for an offboard / user computer to be able to interact with the TurtleBot 4. Therefore, the network must bridge the 2.4 GHz and 5 GHz bands as well. Significant baseline network traffic required to keep the system operational. This means that too many ROS devices/nodes can result in saturating the network and/or increased CPU usage on each of the devices.

Advantages

Disadvantages

Easy to connect to the robot from any device on the network.
The default discovery protocol in ROS 2, so there is no additional setup required.
Supports both CycloneDDS and FastDDS.

Uses multicasting which can be problematic with some Wi-Fi networks, such as university and corporate networks.
Create® 3 must also be connected to Wi-Fi for an offboard / user computer to be able to interact with the TurtleBot 4. Therefore, the network must bridge the 2.4 GHz and 5 GHz bands as well.
Significant baseline network traffic required to keep the system operational. This means that too many ROS devices/nodes can result in saturating the network and/or increased CPU usage on each of the devices.

Discovery Server

Recommended for systems with 1+ robots running complex functionality such as navigation or 2+ robots running simple functionality.

Advantages	Disadvantages
Avoids multicasting issues. Has much lower baseline network traffic and therefore is scalable to many robots. Create® 3 does not need to be connected to WiFi, allowing full TurtleBot 4 functionality with only the Raspberry Pi connected to Wi-Fi and therefore the system can fully operate on a 5 GHz band.	Extra setup is required on the Raspberry Pi, and User PC, particularly if more than one robot is being used. Currently requires FastDDS as the middleware.

Next Steps

Once the networking configuration has been selected, proceed to the corresponding page for instructions on how to configure it, Simple Discovery or Discovery Server.