Built-In Message Support

MATLAB^®supports a large library of ROS message types. This topic covers how MATLAB works with ROS Messages by describing message structure, limitations for ROS messages, and supported ROS data types. Refer to the full list of built-in message types at the end of this article.

For information about ROS 2 messages, seeWork with Basic ROS 2 Messages.

ROS Messages

In MATLAB, ROS messages are stored as message structures or message objects. Message structures are the recommended format as they have better performance over objects when performing initial creation, reading them from rosbag files, accessing nested properties, and performing communication operations over the ROS network. Also, message structures are the only supported message format when generating code throughMATLAB Coder™. For more information on the ROS messages in MATLAB, seeWork with Basic ROS Messages.

ROS Message Structures

A ROS message structure is stored as a MATLAB structure data type with fields based on the message type. Each message type has a specific set of fields with their corresponding values that are individually stored and accessed. You can specifically point to and modify each field on its own. TheMessageTypefield of each message contains the message type as a character vector. Also, you can use therosShowDetailsfunction to view the contents of the message.

Here is a sample'geometry_msgs/Point', created in MATLAB usingrosmessage. It contains 3 fields corresponding to a 3-D point in XYZ coordinates.

pointMsg = rosmessage('geometry_msgs/Point','Dataformat','struct')

pointMsg = struct with fields: MessageType: 'geometry_msgs/Point' X: 0 Y: 0 Z: 0

You can access and modify each field by using thepointMsgstructure.

pointMsg.Y = 2

pointMsg = struct with fields: MessageType: 'geometry_msgs/Point' X: 0 Y: 2 Z: 0

ROS Message Objects

For ROS message objects, all the rules of handle objects apply, including copying, modifying, and other performance considerations. For more information on handle objects, seeHandle Object Behavior. Each handle points to the object for that specific message, which contains the information relevant to that message type. The message type has a built-in structure for the data it contains.

ROS messages store the data relevant to that message type in a way similar to structure arrays. Each message type has a specific set of properties with their corresponding values that are individually stored and accessed. You can specifically point to and modify each property on its own. TheMessageType每个消息包含消息类型的属性as a character vector. Also, you can use theshowdetailsfunction to view the contents of the message.

Here is a sample'geometry_msgs/Point', created in MATLAB usingrosmessage. It contains 3 properties corresponding to a 3-D point in XYZ coordinates.

pointMsg = rosmessage('geometry_msgs/Point')

pointMsg m = ROS点essage with properties: MessageType: 'geometry_msgs/Point' X: 0 Y: 0 Z: 0 Use showdetails to show the contents of the message

You can access and modify each property by using thepointMsghandle.

pointMsg.Y = 2

pointMsg m = ROS点essage with properties: MessageType: 'geometry_msgs/Point' X: 0 Y: 2 Z: 0 Use showdetails to show the contents of the message

Limitations of ROS Messages inMATLAB

Because ROS messages use independent properties, certain messages with multiple values cannot be validated. Because each value can be set separately, the message does not validate the properties as a whole entity. For example, a quaternion message containsw,x,y, andzproperties, but the message does not enforce that the quaternion as a whole is valid. When modifying properties, you should ensure you are maintaining the rules required for that message.

Message properties can also have a variety of data types. MATLAB uses the rules set by ROS to determine what these data types are. However, if they are to be used in calculations, you might have to cast the data types to another value. The ROS data types do not convert directly to MATLAB data types. For a detailed list of ROS data types and their MATLAB equivalent, seeROS Data Type Conversions.

ROS Data Type Conversions

ROS message types have predetermined properties and data types for the values of those properties. These data types must be mapped to MATLAB data types to be used in MATLAB. This table summarizes how ROS data types are converted to MATLAB data types.

ROS Data Type	Description	MATLAB
bool	Boolean / Unsigned 8-bit integer	`logical`
int8	Signed 8-bit integer	`int8`
uint8	Unsigned 8-bit integer	`uint8`
int16	Signed 16-bit integer	`int16`
uint16	Unsigned 16-bit integer	`uint16`
int32	Signed 32-bit integer	`int32`
uint32	Unsigned 32-bit integer	`uint32`
int64	Signed 64-bit integer	`int64`
uint64	Unsigned 64-bit integer	`uint64`
float32	32-bit IEEE floating point	`single`
float64	64-bit IEEE floating point	`double`
string	ASCII string (utf-8 only)	`char`
time	Seconds and nanoseconds as signed 32-bit integers	`Time`object (see`rostime`)
duration	Seconds and nanoseconds as signed 32-bit integers	`Duration`object (see`rosduration`)

Supported Messages

Here is an alphabetized list of supported ROS packages. A package can contain message types, service types, or action types.

To get a full list of supported message types, callrosmsglistin the MATLAB Command Window.

ROS Toolboxsupports ROS Indigo and Hydro platforms, but your own ROS installation may have different message versions. To overwrite our current message catalog, you can utilize theROS Custom Message Supportto generate new message definitions.

When specifying message types, input character vectors must match the character vector listed inrosmsglistexactly. To use custom message types, MATLAB also provides a custom message support package. For more information, seeROS Custom Message Support.

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