GSoC/2020/StatusReports/KitaeKim

Imporove MAVLink integration of Kirogi

The Kirogi is Ground Control Station(GCS) for controlling Unmanned Vehicles like drones developed recently.

It's comparatively young project so it dose not support all standards of MAVLink protocol which is the famous protocol between GCS and UAVs yet.

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

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

Progress Reports

Community Bonding Period

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

I studied about it before GSoC begins but i felt that i need to study about it more.

Through this, i got familiarized much more with the protocol and become able to think clearly what i should implement.

The MAVLink protocol packet is structured in this way:

The protocol uses sub-protocols to extend it's functionality. The sub-protocols are identified using 'MSG ID' section of the packet.

The sub-protocols use 'PAYLOAD' section to transport information for the sub-protocol. (e.g., arguments for the sub-protocol)

The thing i need to focus on about the protocol during phase 1 is:

1. Heartbeat Protocol: It is used to identify existence of system along with its system id, component id, vehicle type, component type, flight mode and flight stack. This allows us to discover system connected to the network and notice when they have been disconnected and handle incoming messages appropriately based on type of vehicle and route messages to system on different interface.
2. Message Channel: It is used by helper functions provided by MAVLink library. The MAVLink library manages buffers per channels internally. So we need to manage channels to manage multiple vehicles. It seems one channel per one connection is suffice.

The protocol can control up to 255 vehicles at the same time because 'SYS ID' section of the packet is 1 byte size.

So i will implement vehicle manager for managing multiple vehicles during the phase 1. The vehicle manager should be able to identify vehicles based on the heartbeat message, manage vehicle's channel and parse incoming messages based on the vehicle's channel.

Second thing i did during this period is reading code of Kirogi and QGroundControl in comparison. QGroundControl is the most famous GCS for the MAVLink out there.

Through this i learned about MAVLink protocol much more and the way the QGroundControl supports the protocol.

The QGroundControl has MultiVehicleManager and LinkManager class which are used to manage vehicles and links.

The MultiVehicleManager creates vehicle object when incoming message has unknown system id just like what i wrote on the proposal. The vehicle object contains information for the vehicle like system id.

The link in QGroundControl contains actual interface like QSerialPort and information for that like port number.

The LinkManager creates link object when user wants to create new one. One thing interesting is that the link class inherits QThread so that it can run on new thread by creating it. But the Kirogi community's developers are quite skeptical about this because one or up to three thread seems enough to handle incoming messages of 255 vehicles.

Both have pointer to toolbox which contains pointer to MultiVehicleManager, LinkManager, MAVLinkProtocol and name a few. So they can reference each other when it's needed.

The link passes incoming message to MAVLinkProtocol class. It dose MAVLink-specific jobs like parsing packet to message or checking packet sequence and measuring packet lost using 'SEQ' section of the packet. It passes the parsed message to every component like vehicle object or LinkManager. This looks quite inefficient because every components need to process message to check if it's destination is itself.

The Kirogi aims to support various firmwares like tello, parrot, ardupilot and px4. For that purpose it uses KPlugin to load functionalities dynamically in runtime.

One thing interesting is that the Kirogi's Ui is general to all of plugins. The Kirogi uses same QML code for the Ui and loads information from abstract classes like AbstractVehicle. Plugin-specific classes inherit those abstract classes.

This generality was obstacle to me because it seems, for me, different model needs different Ui. I'm still thinking about this.

MAVLink plugin of Kirogi consists of two main components:

1. MAVLinkVehicle: This is used to store information of vehicle. This also processes incoming message and manage connection.
2. MAVLinkConnection: This is used to establish connection. This class receives and parses incoming message and passes it to MAVLinkVehicle. Currently it supports UDP connection only.

It's apparent that we need more classes to manage multiple vehicles and connections.

Related Links

Project Proposal

Improve MAVLink integration of Kirogi

Personal Repository

Kitae Kim / Kirogi