PX4 PWM Output

Configure PWM outputs for servo motors and ESC control

PX4 PWM Output will be removed in a future release. For more information, see Version History.

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 Utility Blocks

Description

The PX4 PWM Output block helps you to configure the PWM output from the PX4^® flight controller board. The block accepts time value (in microseconds) that represents the ON period of PWM signal for a particular channel, and passes the same to the corresponding PWM channels on the board.

The PX4 PWM Output block also accepts signals for arming the flight controller.

During Connected I/O simulation, this block writes data to the peripherals of the hardware.

During Connected I/O simulation, this block writes data to the peripherals of the hardware.

Configure Actuators

For Firmware version 1.14, the PWM & AUX pins need to be configured in QGroundControl before the PWM Output block can be used in Simulink. To do this, QGroundControl version 4.2.3 is needed which can be downloaded from this location.

Note

Configuring the actuators is not required for Hardware-in-the-loop or PX4 Host Target simulations.

To configure the actuators, perform these steps.

1. Perform the Hardware setup process for your Autopilot.

2. Launch QGroundControl 4.2.8 (QGC) and allow it connect to your Autopilot.

3. Once QGC is connected, go to Vehicle Setup -> Actuators tab.

   

4. Assign the following sequence of Motors against each Main Channel.

   

   It is recommended to change the Minimum PWM value of each channel to 1000 and Maximum PWM value to 2000.

5. Assign the following sequence of Motors against each AUX Channel.

   

Examples

Getting Started with PWM Blocks for PX4 Autopilots

Use the PX4 PWM Output block to generate signals on the PWM pins of a Pixhawk Series controller, and verify the PWM values.

• Open Model

Ports

Input

Arm — Arm the PX4 flight controller

0 (default) | 1

Enable signal for arming the PX4 flight controller.

Data Types: Boolean

Set failsafe — Enforce failsafe for PX4 flight controller

0 (default) | 1

Enforce failsafe values even though the failsafe conditions might or might not have occurred. You can specify the failsafe values in the Configuration Parameters dialog box in Simulink.

Note

If you are using PX4 firmware 1.12.3, the value at Set failsafe input port is not valid if you use AUX channels for PWM.

Data Types: Boolean

Ch x — Inputs that accept PWM ON values

0 (default) | 1

Connect the Ch x inputs to signals that represent PWM ON values (in microseconds)

Dependencies

The required Ch inputs are selected using the PWM Channels parameter.

Data Types: uint16

Parameters

Main tab

Select PWM Device — Channel category to identify the channels that you are going to select

Main (default) | Aux

Select the category (Main or AUX) to identify and select the corresponding channels. After you select this category, you can select the channels in the parameter list, for Main and AUX, separately.

PWM Channels — Channels to which you want to send the PWM ON time values

Channel numbers

Select the channels to which you want to send the values for PWM ON time (the channels to which you connect servo motors or ESC). The Ch inputs to the block appear based on the selection in this parameter list.

Note

Ensure that you select all the channels that belong to the same channel group. If you need to connect to PWM channels that are in different groups, select all channels in all the desired groups. Only one PX4 PWM Output block per channel category (Main or AUX) is allowed in the entire Simulink model.

Tip

To identify the channel groups in the Pixhawk Series flight controller board, use QGroundControl application on your host computer:

1. Open QGroundControl.

2. Connect the Pixhawk Series flight controller board to the USB port of the host computer.

3. In QGroundControl, go to Mavlink Console, and do the following:

   • To identify the Main channels and their groups, enter the command pwm info.

   • To identify the Aux channels and their groups, enter the command pwm info -d /dev/pwm_output1

Version History

Introduced in R2018b

R2024b: To be removed in a future release

The PX4 PWM Output function will be removed in a future release. Use the PX4 Actuator Write block instead.

For information to convert the PX4 PWM Output in your Simulink model to a PX4 Actuator Write block, see Convert PX4 PWM Output Block to PX4 Actuator Write Block.