DJI OSDK

ROS 2 Humble only

The DJI OSDK platform isn't supported on ROS 2 Jazzy yet. Build it on Humble.

The DJI OSDK platform flies DJI Matrice drones through the DJI Onboard SDK. It works with the Matrice 210 V2, the Matrice 210 RTK V2 and the Matrice 300 RTK. DJI's flight controller keeps flying the drone, and Aerostack2 sends it velocity setpoints from a companion computer. The drone takes off and lands by itself.

For newer DJI drones such as the Matrice 350 RTK or the M30, use the DJI PSDK platform instead.

Install

Follow DJI's device connection guide to wire the companion computer to the drone. A UART link carries the flight commands, and an optional USB link gives access to the camera, the gimbal and advanced sensing. Register an app on the DJI developer site to get an app ID and key.

Then build the platform. The build downloads the Onboard SDK, so it needs internet access.

cd ~/aerostack2_ws/src
git clone https://github.com/aerostack2/as2_platform_dji_osdk.git
cd ~/aerostack2_ws
rosdep install --from-paths src --ignore-src -y
colcon build --symlink-install --packages-up-to as2_platform_dji_osdk

The user running the platform needs access to the serial and USB devices, through udev rules or group membership.

Launch

The user configuration file holds the app credentials and the ports the drone is wired to:

config/user_config.txt

app_id : 123456
app_key : 0123456789abcdefghijklmnopqrstuvwxyz
device : /dev/ttyUSB0
baudrate : 921600
acm_port : /dev/ttyACM0

ros2 launch as2_platform_dji_osdk as2_platform_dji_osdk_launch.py \
  namespace:=drone0 \
  user_config_file:=config/user_config.txt

The platform activates the app with DJI when it starts.

Parameter	Default	What it does
`cmd_freq`	100.0	How often commands are sent, in Hz
`info_freq`	10.0	How often `platform/info` is published, in Hz
`enable_advanced_sensing`	false	Give access to the cameras and other sensors over USB
`publish_camera`	true	Publish the main camera, when advanced sensing is on
`enable_mop_channel`	false	Open a MOP channel to talk with a DJI mobile app

Control modes

Control mode	Yaw
Hover
Speed	Angle or rate

That fits the PID speed controller. Velocities are sent in the odom frame and converted to DJI's north, east and up.

Topics

Topic	Contents
`sensor_measurements/odom`	The drone's fused GPS position, converted to a local frame
`sensor_measurements/gps`	GPS fixes
`sensor_measurements/battery`	The battery state
`sensor_measurements/image_raw/image`	The main camera, with advanced sensing on
`sensor_measurements/gimbal/attitude`	The gimbal's attitude
`platform/info`	The platform status

The gimbal is commanded on platform/gimbal/gimbal_command. Publishing true on camera/trigger takes a photo.

With the rest of the stack

Use the raw_odometry estimator plugin on the drone's odometry, and the platform's own take-off and landing:

config/config.yaml

/**:
  state_estimator:
    ros__parameters:
      plugin_name: "raw_odometry"
  TakeoffBehavior:
    ros__parameters:
      takeoff_plugin_name: "takeoff_plugin_platform"
  LandBehavior:
    ros__parameters:
      land_plugin_name: "land_plugin_platform"

Things to know

Odometry starts at the first GPS fix with at least four satellites, and nothing is published before that. The drone needs GPS to fly with this platform.
Arming doesn't start the motors. They start when the drone takes off.
Stopping the platform triggers DJI's emergency brake, which holds the drone in place.
The kill switch isn't available. Use the remote control to stop the motors.

The project_dji_osdk repository has a complete setup for a Matrice drone.