Accelerometer

Read sensor_accel uORB topic and obtain three dimensional linear acceleration

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

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Libraries:
UAV Toolbox Support Package for PX4 Autopilots / PX4 Sensor Blocks

Description

The Accelerometer block reads the sensor_accel uORB topic and outputs the linear acceleration of the PX4 Autopilot board along the x, y and z axis. The block also outputs the timestamp.

On each simulation step, the block checks if a new message is available on the sensor_accel topic. If a new message is available, the block retrieves the message and outputs it, and the timestamp is updated. If a new message is not available, the block outputs the last updated uORB message and the timestamp is not updated. If a message has not been received since the start of the simulation, the outputs are zeroes.

During Normal mode simulation, the block outputs zeroes.

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

Ports

Output

Status — Status of the received uORB data

0 | 1

The Status output indicates if the sensor_accel uORB message was received during a previous time step or not. A value of 0 indicates that the uORB data at the outputs 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 new messages received in the uORB network.

Data Types: Boolean

X — Linear acceleration along the x-axis

scalar (㎨)

The linear acceleration along the x-axis of the PX4 Autopilot board, as read from the sensor_accel uORB topic.

Data Types: single

Y — Linear acceleration along the y-axis

scalar (㎨)

The linear acceleration along the y-axis of the PX4 Autopilot board, as read from the sensor_accel uORB topic.

Data Types: single

Z — Linear acceleration along the z-axis

scalar (㎨)

The linear acceleration along the z-axis of the PX4 Autopilot board, as read from the sensor_accel uORB topic.

Data Types: single

Timestamp — Timestamp of the received uORB data

time in microseconds

Represents the time (since the PX4 system start) when the sensor_accel topic was last updated.

Data Types: double

To see more output options for the sensor_accel uorb topic, use the PX4 uORB Read block, subscribe to the topic, and select other output options.

Parameters

Main tab

Timestamp — Enable timestamp value as one of the outputs

off (default) | on

Select this parameter to output the timestamp.

Sample time — Interval at which the block reads values

1/250 (default) | any non-negative value that is a multiple of 1/250 | -1

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

Wait until data received — Wait until requested data is available

off (default) | on

• 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 the data is available, the block outputs the selected values, and the Status port is set to 0.

  The board waits for the message in Blocking Mode for the time mentioned in the Timeout in seconds. If the data is not received before the timeout, then the Status port outputs 1 and the block outputs the last received value.

  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.

Timeout in seconds — Time to wait until the data is received

1e-3 (default) | (0, 2^32/1000]

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