B4A Library DJI Drones

DJI Drones are very popular and advanced drones. DJI provides an Android app that is used during flights to control the drone.
The Android device connects to the remote controller with a USB cable (USB debug mode should be enabled).

DJI are also providing a feature-rich SDK that allows us, developers, to create alternative applications to control the drone. It is quite amazing to be able to easily program a drone to do all kinds of sophisticated tasks.

The following video is an example created with B4A and the DJI library. On the left side you can see the drone camera feed and various parameters. On the right side there is a standard Google Map. Touching on a point in the map starts a hotspot mission. The drone will rotate automatically around the spot.



How to use

1. Register with DJI: https://developer.dji.com/ and create an app in the User Center page. You will see an App Key that you need to add to the manifest editor.
The bundle identifier must match your app package name.
2. Add this code to the manifest editor:

Code:

'************ DJI SDK '***********
SetApplicationAttribute(android:name, "anywheresoftware.b4a.objects.BaseApplication")
SetApplicationAttribute(android:largeHeap, "true")
AddPermission(android.permission.BLUETOOTH)
AddPermission(android.permission.BLUETOOTH_ADMIN)
AddPermission(android.permission.VIBRATE)
AddPermission(android.permission.INTERNET)
AddPermission(android.permission.ACCESS_WIFI_STATE)
AddPermission(android.permission.WAKE_LOCK)
AddPermission(android.permission.ACCESS_COARSE_LOCATION)
AddPermission(android.permission.ACCESS_NETWORK_STATE)
AddPermission(android.permission.ACCESS_FINE_LOCATION)
AddPermission(android.permission.CHANGE_WIFI_STATE)
AddPermission(android.permission.MOUNT_UNMOUNT_FILESYSTEMS)
AddPermission(android.permission.WRITE_EXTERNAL_STORAGE)
AddPermission(android.permission.READ_EXTERNAL_STORAGE)
AddPermission(android.permission.SYSTEM_ALERT_WINDOW)
AddPermission(android.permission.READ_PHONE_STATE)
AddManifestText(

<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.camera.autofocus" />
<uses-feature
  android:name="android.hardware.usb.host"
  android:required="false" />
<uses-feature
  android:name="android.hardware.usb.accessory"
  android:required="true" />
<!-- Permissions and features -->
)
AddApplicationText(
  <uses-library android:name="com.android.future.usb.accessory" />
  <meta-data
  android:name="com.dji.sdk.API_KEY"
  android:value="XXXXXXXXXXXXXXX" />
  <activity
  android:name="dji.sdk.sdkmanager.DJIAoaControllerActivity"
  android:theme="@android:style/Theme.Translucent" >
  <intent-filter>
  <action android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED" />
  </intent-filter>
  <meta-data
  android:name="android.hardware.usb.action.USB_ACCESSORY_ATTACHED"
  android:resource="@xml/accessory_filter" />
  </activity>
  <service android:name="dji.sdk.sdkmanager.DJIGlobalService" >
  </service>
)

Replace XXXXXXXXXX with your App key.
3. Add to the main activity code:

Code:

#BridgeLogger: true
#MultiDex: true
#AdditionalJar: dji-sdk-provided-4.4.1, ReferenceOnly

4. Initialize the SDK when the application starts. The RegisteredResult event will be raised. If successful then call sdk.StartConnectionToProduct to start a connection.
4. The ProductChanged event will be raised. If AircraftData is not Null then you are good to go and can initialize the DJIAircraft object and the other features (see how it is done in the example).
5. Most of the operations are asynchronous. They are built to work with the new Wait For keyword.
6. Expect disconnections and other errors.

See the attached example.

Tips & Notes

- Make sure that you are able to connect to the drone with the DJI app. Not all Android devices have proper support for USB connected devices.
- You will see a dialog that asks you whether you always want to start the DJI app when the USB is connected. Click on "This time only". Otherwise you will need to uninstall the DJI app as it will get an exclusive permission to use the USB device.
- Use B4A-Bridge to connect the IDE to the Android device.
- Supported drones: https://developer.dji.com/mobile-sd.../product_introduction.html#supported-products
- Use the simulator to test your app. It works well.
https://developer.dji.com/mobile-sd...on-development-workflow/workflow-testing.html

- Don't fly the drone indoors.
- Check the GPS status. All the nice automatic features will fail without the GPS. Should be 4 or 5.
- Make sure that the home location is set before flight.
- Always be prepared to manually control the drone.

Download the native libraries and copy them to the additional libraries folder:
www.b4x.com/android/files/dji.zip
Download the attached library and copy it as well.

Version 4.41 is released. It is based on DJI SDK v4.41. It supports waypoint missions
It requires B4A v8+.
The minimum Android version is 5.0.

Two examples are attached:
DroneFirst - A basic example for generic flights.
DroneMission - Example of using WaypointMissionOperator to create a waypoint mission.
The DroneMission demonstrates how to request the permissions when setting targetSdkVersion to 26.

The library source code is attached.

 

Another example is attached. This one adds a MJPEG server to the app. It allows other clients to connect and see the camera feed.
The url is displayed in the app screen.



The compiled APK is available here: www.b4x.com/android/files/DroneMJPEG.apk
Consider it a beta app and always be prepared to manually control the drone.

 

The shadow can be added with this code:

Code:

Sub SetTextShadow(lbl As Label)
   Dim jo As JavaObject = lbl
   Dim radius = 2dip, dx = 0dip, dy = 0dip As Float
   jo.RunMethod("setShadowLayer", Array(radius, dx, dy, Colors.Yellow))
End Sub

 

Please start a new thread for this.

Which drone are you using?

 

I was waiting for demand

It should be very simple to add support for other types of missions. I can also show you how it can be done with JavaObject.

Start with this example and once you get it working (the USB exclusive permission can be a bit annoying) we can extend it.

 

I think that it will work.

 

It can take a minute for the app to be installed due to the library size.

Connect the Android device with a USB cable to the PC and enable USB debug mode. It will allow you to see the logs.

 

What happens when you run the example from the first post?