GSoC/2020/StatusReports/KitaeKim

Imporove MAVLink integration of Kirogi

The Kirogi is a Ground Control Station(GCS) for managing Unmanned Aerial Vehicles like drones.

It's comparatively young project so it dose not support all standards of MAVLink protocol which is used to communicate with drone's firmware like PX4 and Ardupilot.

The goal is to imporove MAVLink protocol integration of Kirogi so that it supports most functionalities of the protocol.

Mentors: Tomaz Canabrava, Eike Hein, Patrick José Pereira, Sung Jae Cho

Progress Reports

Community Bonding Period

Study about MAVLink protocol. - Done
Read code of Kirogi and QGroundControl in comparison. - Done
Study about Qt and C++ development. - In progress

The first thing i did during this period is studying more about MAVLink protocol.

The MAVLink protocol packet is structured in this way:

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This protocol uses sub-protocols to extend it's functionality. Those are identified using 'MSG ID' section of the packet. Additional information for sub-protocol is transported through 'PAYLOAD' section of the packet.

First feature that will be implemented during phase 1 is integration of heartbeat protocol.

The heartbeat protocol is one of MAVLink's sub-protocols. It is used to identify existence of vehicle along with its properties. This allows us to discover vehicle connected to the network and notice when they have been disconnected. It also allows us to handle incoming messages appropriately based on type of the vehicle and route messages to system on different interface.

Second thing i did during this period is reading code of Kirogi and QGroundControl in comparison. The QGroundControl is a standard de facto control station for MAVLink drones.

The QGroundControl has MultiVehicleManager and LinkManager which are used to manage vehicles and links as name suggests. The MultiVehicleManager creates vehicle object when incoming message has unknown system id. The vehicle object contains information of the actual vehicle like system id and connection status. The LinkManager creates link object when user wants to establish new connection. Both have pointer to ToolBox which contains pointer to main components like MultiVehicleManager and LinkManager so they can reference each other when it's needed.

The Kirogi aims to support various firmwares including PX4 and Ardupilot. For that, it uses KPlugin.

Kirogi's UI is general to all plugins. I felt that this generality prevent me to implement various features for plugins. It would be modified to load some plugin-specific elements at runtime in future.

Main components of MAVLink plugin are MAVLinkVehicle and MAVLinkConnection. The MAVLinkVehicle contains information of the actual vehicle. This class has method to processes incoming message and manage connection. The MAVLinkConnection contains QUdpSocket and method to receive and parse incoming messages. Other plugins of Kirogi have same structure.

It seems implementing all functionalities of MAVLink not breaking general structure of Kirogi is quite challenging.

Coding Period Phase 1

Improve integration of command protocol. - Done
Implement vehicle manager for managing multiple vehicles. - Done
Write unit tests of implementation. - Cancelled
Write a documentation about implementation. - Done
Study about Qt and C++ development. - Keep doing

Command protocol specifies that every commands should be followed by ack message from the vehicle that receives the command. If no ack message was received, GCS should resend message until it reaches max count. This feature was implemented before GSoC begins.

New MAVLinkVehicleManager class creates vehicle object when incoming message has unknown system id. It stores vehicle object in MAVLinkVehicleModel class. This class inherits from QAbstractList so that in can provide list of vehicles to UI.

The Kirogi use KPlugin XT but it can't configure plugin-specific options. The MAVLinkConnectionConfig class is for configuring MAVLink's UDP/TCP/Serial connection. This class is connected to UI so that users can configure options using methods.

About the future works, Kirogi's UI is generic to every plugins but it seems some plugins need it's own UI. In example, Plan Manager for MAVLink plugin. My conclusion is that I can't implement UI that is really generic to all plugins so I need to load some of UI elements at runtime based on the plugin. 'Check List', 'Global Drawer', 'Navigation Map', 'Settings' pages would be appropriate places to load those elements.

Some miscellaneous works like renaming some redundant variables or modifying existing classes are done during this phase.

I was planning to adopt Test-Driven development at the first time, but it seems there are many other things to learn like how drone's firmware works so that I have not enough time to study and adopt it.

Coding Period Phase 2

Support TCP and Serial connection. - Done
Implement UI for selecting multiple vehicles. - Done
Divide PR into smaller pieces. - In progress
Write a documentation about implementation. - Done
Study about Qt and C++ development. - Keep doing

Because there's no code for TCP and Serial connection in Kirogi's codebase, I created classes for connection abstraction including 'ConnectionConfiguration', 'TcpConfiguraiton' and so on.

There's an 'AbstractConnection' class for connection abstraction but if we want to manage it's properties at Kirogi's base level(libkirogi and QML), we have to provide a generic way to manage connection's property.

We can't just use same connection class for all plugins because the way how connection-related procedures defined depends on the type of drone.

At the first time, I was thinking to implement things like 'AbstractUdpConnection', 'AbstractTcpConnection' that defines common properties of those connections and implement plugin's connection inheriting them.

But I found that some connections need more than one types of methods to operate. In example, some connection may use TCP for handshaking and UDP for communicating.

So I decided to mix 'AbstractConnection' and some kind of connection configuration class to implement plugin's connection. In this way, we can implement 'ArbitraryConnection' mixing 'AbstractConnection' with 'UdpConfiguration' and 'TcpConfiguration' which inherits 'ConnectionConfiguration'.

I implemented connection classes for mavlink like 'MAVLinkUdpConnection', 'MAVLinkTcpConnection' and 'MAVLinkSerialConnection' using them.

I also wrote code for managing multiple connections as well although it's not a thing that I planned do at this phase. That's because I thought that I had to think about implementations that make use of connection-related classes I wrote while actually writing them.

I also implemented basic drawler for selecting vehicle inside of 'Check List' element.

I was doing everything in one branch and created one PR for everything which results in that my mentors couldn't review my work efficiently. So I started break things into smaller pieces.

Coding Period Phase 3

Divide PR into smaller pieces. - Done
Implement connection manager for managing multiple connections. - Done
Implement UI for managing multiple connections. - Not done
Write a documentation about implementation. - Done
Study about Qt and C++ development. - Keep doing

I divided the branch that I mentioned previous progress report into four smaller branches.

One for basic chamges for all of other branches, others for connection abstraction, vehicle management and connection management. Latter three branches depend on first one and one for connection management depends on conneciton abstraction.

I also implemented connection manager for managing multiple connections. new 'AbstractConnectionModel' class, which is used for managing connections, creates new configuration with default value when user wants to create new connection. Then user can edit it and create connection based on the configuraiton.

When user wants to edit existing one, it duplicates configuration of selected connection and user can edit it. When user choose to save it, the model copies value that user wrote into existing connection's configuration.

The reason why I decided to copy values rather than replacing existing connection with new connection is because there maybe a vehicle that uses connection that is being edited. In that case, it's more easier copy values than replacing connection object and make vehicle to use it.

This class also provides list of available serial port. Some invalid ports will be filtered to prevent users to select them.

I was thinking to implement basic UI for managing connections but I didn't. because my mentors pointed out that it's better to manage vehicles and connections in more generic way rather than implementing managers for each plugin. In this way, users can control different types of vehicles like parrot bebop and pixhawk at the same time. It seems good idea for me so I'll start implementing UI for manging vehicles and connections after backend architecture for that feature gets specifed.

Blog Writings

Branches and PRs

Contacts

Email: [email protected]

LinkedIn: https://www.linkedin.com/in/kitae-kim-511032182/

Footnotes

↑ https://mavlink.io/en/

[1] ttps://mavlink.io/en/

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