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PX4 uORB Read

Read uORB data for the specified uORB topic

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Add-On Required: This feature requires the UAV Toolbox Support Package for PX4 Autopilots add-on.

  • PX4 uORB Read block

Libraries:
UAV Toolbox Support Package for PX4 Autopilots / PX4 uORB Read and Write Blocks

Description

The PX4 uORB Read block creates a Simulink® nonvirtual bus that corresponds to the specified uORB topic.

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 uORB message. If a message has not been received since the start of the simulation, Msg outputs a blank message.

During Normal mode simulation, the block outputs zeroes.

During Connected I/O simulation, this block reads data from the peripherals of the hardware.

Examples

Getting Started with uORB Blocks for PX4 Autopilots Support Package

Getting Started with uORB Blocks for PX4 Autopilots Support Package

Use the PX4 uORB Read and the PX4 uORB Write blocks in UAV Toolbox Support Package for PX4® Autopilots to read and write uORB messages in the uORB network.

Ports

Output

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uORB message, returned as a nonvirtual bus. The type of uORB message is specified using the parameter, Topic to subscribe to.

Connect a Bus Selector block to the Msg output to extract the signals.

Data Types: bus

The Status output indicates if the uORB message was received during a previous time step or not. A value of 0 indicates that the uORB data at the Msg output is the latest, and a value of 1 indicates that the uORB data was received during the previous time step.

This output can be used to trigger subsystems for processing the new messages received in the uORB network.

Data Types: Boolean

Parameters

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Main tab

Select the name of the uORB topic that the block needs to subscribe to read the uORB data. Click Select to browse the topic names available in the Firmware/msg folder of the px4 directory that you downloaded.

Select the instance of the uORB topic that the block needs to subscribe to read the uORB data.

Dependencies

This parameter appears only if you select a topic that supports multiple instances, in the Topic to subscribe to parameter.

For example, the actuator_controls topic supports multiple instances and you can select one instance from the drop-down.

Enter the time interval at which the block reads values from the uORB network.

When you set this parameter to -1, Simulink determines the best sample time for the block based on the block context within the model.

Advanced Tab

  • When you select this option, the read operation runs in Blocking Mode. The read operation is blocked while waiting for the requested data to be available. When waiting for the data, the Status port displays same values from the previous time step. When the data become available, the Data port outputs data bytes, and the Status port changes to 0.

    A task overrun occurs if the target hardware is still waiting for the data to be available when the next read operation is scheduled to begin.

    To fix overruns, Increase the time step by using the Sample time parameter.

  • When you clear this option, the read operation runs in Non-Blocking Mode. In this mode, the block does not wait for the requested data to be available.

Specify the amount of time that the block waits for the data during each time step, if the Wait until data received parameter is selected. If timeout occurs, the read operation is aborted.

Dependencies

This parameter appears only when you select the Wait until data received parameter.

Version History

Introduced in R2018b

See Also

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