Receive messages from ROS network
Robotics System Toolbox / ROS
The Subscribe block creates a Simulink® nonvirtual bus that corresponds to the specified ROS message type. The block uses the node of the Simulink model to create a ROS subscriber for a specific topic. This node is created when the model runs and is deleted when the model terminates. If the model does not have a node, the block creates one.
On each simulation step, the block checks if a new message is available on the specific topic.If a new message is available, the block retrieves the message and converts it to a Simulink bus signal. The Msg port outputs this new message. If a new message is not available, Msg outputs the last received ROS message. If a message has not been received since the start of the simulation, Msg outputs a blank message.
IsNew— New message indicator
New message indicator, returned as a logical. If the output
1, then a new message was received since the
last sample hit. This output can be used to trigger subsystems for
processing new messages received in the ROS network.
Msg— ROS message
ROS message, returned as a nonvirtual bus. The type of ROS message is specified in the Message type parameter. The Subscribe block outputs blank messages until it receives a message on the topic name you specify. These blank messages allow you to create and test full models before the rest of the network has been setup.
Topic source— Source for specifying topic name
Select from ROS network|
Specify your own
Source for specifying the topic name, specified as one of the following:
Select from ROS network — Use
Select to select a topic name. The
Topic and Message type
parameters are set automatically. You must be connected to a ROS
Specify your own — Enter a topic
name in Topic and specify its message type in
Message type. You must match a topic name
Topic— Topic name to subscribe to
Topic name to subscribe to, specified as a string. When Topic
source is set to
Select from ROS
network, use Select to select a topic
from the ROS network. You must be connected to a ROS network to get a list
of topics. Otherwise, set Topic source to
Specify your own and specify the topic you
Message type— ROS message type
ROS message type, specified as a string. Use Select to select from a full list of supported ROS messages. Service message types are not supported and are not included in the list.
Sample time— Interval between outputs
–1(default) | scalar
Interval between outputs, specified as a scalar. In simulation, the sample time follows simulation time and not actual wall-block time.
This default value indicates that the block sample time is inherited.
For more information about the inherited sample time type, see Specify Sample Time (Simulink).
Length of subscribe callback queue— Message queue length
1(default) | integer
Message queue length in code generation, specified as an integer. In
simulation, the message queue is always 1 and cannot be adjusted. To ensure
each message is caught, use a smaller model step or only execute the model
You can also set the addresses for the ROS master and node host by clicking the Configure network addresses link in the block.