MAVLink Protocol and Applications Guide

MAVLink Protocol is a lightweight, header-only protocol used for communicating between a drone and its autopilot system. It's designed to be efficient and reliable, making it a popular choice for many drone applications.

MAVLink is developed by Jonathan H. Westenberg and is an open-source protocol. This means that it's free to use and modify, which has contributed to its widespread adoption in the drone industry.

MAVLink is used in a variety of drone applications, including aerial photography, surveying, and inspection. It's also used in drones for search and rescue missions, where its reliability and efficiency are critical.

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MAVLink is a lightweight protocol designed for efficiently sending messages over unreliable low-bandwidth radio links. It's perfect for applications where data needs to be transmitted quickly and reliably, such as in drone communication.

MAVLink messages are the fundamental building blocks of the protocol, consisting of a name, id, and fields containing relevant data. They're deliberately lightweight, with a constrained size, and no semantics for resending and acknowledgement.

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The protocol relies on each end of the communication having a shared definition of what messages are being sent. This means both ends must use libraries generated from the same XML definition.

MAVLink messages can be used for streaming telemetry or status information, and for sending commands where no acknowledgement is required. For example, setpoint commands sent at high rate.

MAVLink messages, commands, and enumerations are defined in XML definition files. These files are used to create programming-language-specific libraries for sending and receiving messages.

Here are the different types of XML definition files used in MAVLink:

These definition files are used to standardize MAVLink messages, commands, and enumerations, making it easier for different systems to communicate with each other.

You can install MAVLink on specific versions of Ubuntu. These versions are Ubuntu LTS 20.04 and 22.04.

MAVLink can be installed using a terminal command. The command is specific to the Ubuntu versions mentioned earlier.

MAVLink is a lightweight and efficient protocol that's perfect for applications with limited communication bandwidth. It has just 8 bytes of overhead per packet in MAVLink 1, and 14 bytes in MAVLink 2, which is a more secure and extensible protocol.

MAVLink is known for its reliability, having been used since 2009 to communicate between various vehicles, ground stations, and other nodes over challenging communication channels.

The protocol is highly adaptable, allowing use with many different programming languages and microcontrollers, such as ARM7, ATMega, and STM32.

One of the key benefits of MAVLink is its ability to handle a large number of concurrent systems on the network, up to 255 systems.

MAVLink enables both offboard and onboard communications, making it ideal for applications such as drone-to-camera communication.

Here are some technical details of MAVLink:

MAVLink offers a variety of development tools to help you get started with your project. The MAVLink organisation provides tools like mavgen, mavgenerate and rust-mavlink, which support multiple languages.

These tools can generate libraries for various programming languages, including C, C++11, Python, Java, and JavaScript. For example, the mavgen tool can generate a Python library that supports both MAVLink v1 and MAVLink 2, and also includes signing support.

Here are some of the languages and tools supported by MAVLink:

Project Generators/Languages are a crucial part of any development project. They help you generate code for specific languages, making it easier to integrate MAVLink into your project.

The MAVLink organisation provides three main tools for generating code: mavgen, mavgenerate, and rust-mavlink. These tools support a wide range of languages, including C, C++11, Python, Java, and many more.

Here's a breakdown of the languages supported by each tool:

External Generators/Languages are also available, provided by independent projects. These include fastMavlink, clj-mavlink, dart_mavlink, and more.

fastMavlink, for example, is a highly efficient C library with support for routing and MAVLink 2. It also has a Python code generator and a test suite.

clj-mavlink, on the other hand, is a Clojure MAVLink binding with support for MAVLink 2 and signing.

These external generators offer a range of options for developers, allowing them to choose the best tool for their specific needs.

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To include headers in CMake, install them locally into a directory like "install". You can then use find_package to get the dependency in CMakeLists.txt.

You'll need to pass the local install directory to cmake, which will depend on your directory structure. For example, you might use something like "-DCMAKE_PREFIX_PATH=/path/to/install".

Installing headers locally is a good idea, as it allows you to avoid conflicts with system-installed versions. This is especially important for header-only libraries like MAVLink.

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Prebuilt C Libraries are a great resource for developers working with MAVLink. They provide pre-generated C libraries for the latest versions of all message specifications and dialects.

These libraries are available for both MAVLink 1 and 2, making it easy to get started with either version.

The C libraries are auto-generated and can be accessed through the 'c_library_v2' and 'c_library_v1' files.

Using these libraries can save you a significant amount of time and effort, especially if you're working on a project that requires frequent updates to the MAVLink code.

Here are the available prebuilt C libraries:

The MAVLink protocol is hosted under the governance of the Dronecode Project. This means that the protocol is maintained and developed by a community-driven organization.

The Dronecode Project is responsible for overseeing the development and maintenance of MAVLink, ensuring that it remains a widely-used and reliable protocol for drone communication.

The license agreement for MAVLink is quite flexible. The message definition XML files and the generated C-language version of MAVLink are made available under the MIT-license.

This means you can use MAVLink in any closed-source application without having to publish the source code of your project.

The MAVLink generator toolchain, on the other hand, is licensed under the Lesser General Public License (version 3) of the Free Software Foundation (LGPLv3).

This license allows for more freedom in how you can use the toolchain, but still requires you to share any changes you make to the code.

MAVLink documentation is licensed under CC BY 4.0, which allows for free use and sharing of the documentation as long as you give proper credit to the original creators.

The governance of open-source projects is often a crucial aspect of their success. The MAVLink protocol is hosted under the governance of the Dronecode Project.

This means that the Dronecode Project has a significant role in shaping the future of MAVLink and ensuring its continued development and improvement. The Dronecode Project is a collaborative effort that brings together industry leaders and developers to advance the state of drone technology.

The fact that MAVLink is hosted under the governance of the Dronecode Project suggests a high level of commitment to open-source principles and community involvement. This can be a major advantage for users and developers who want to contribute to the project.

MAVLink is used for communication between a Ground Control Station (GCS) and unmanned vehicles, and also for the inter-communication of the vehicle's subsystems.

It can be used to transmit the vehicle's orientation, GPS location, and speed. This makes it a crucial component for many applications.

MAVLink is compatible with many projects, which can be a big advantage in terms of integration and compatibility. Here are some examples of areas where MAVLink is used:

In the world of unmanned vehicles, communication is key. It's used mostly for communication between a Ground Control Station (GCS) and the vehicles.

The system also enables inter-communication between the vehicle's subsystems. This allows for efficient data exchange and coordination.

It can be used to transmit the vehicle's orientation, GPS location, and speed. This information is vital for navigation and control.

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The MAVLink ecosystem is a vast network of projects that use the MAVLink communication protocol. This has led to a high degree of compatibility between them.

MAVLink is used in various industries such as robotics engineering, where it's applied to unmanned aerial vehicles. These vehicles use MAVLink for efficient communication.

Serial buses are also a key part of the MAVLink ecosystem, allowing for reliable data transmission. This is particularly useful in avionics applications.

Wireless connectivity is another aspect of MAVLink, enabling devices to communicate over long distances. This is beneficial in robotics engineering and unmanned aerial vehicles.

MAVLink is also used in application layer protocols, providing a standardized way of communication. This is essential in ensuring seamless integration between different systems.

Here's a list of some of the areas where MAVLink is used:

PX4 is a key player in the MAVLink ecosystem. It releases build common.xml MAVLink definitions by default, ensuring maximum compatibility with MAVLink ground stations, libraries, and external components.

These definitions are included from development.xml on SITL and common.xml for other boards. You'll need to work with the MAVLink team to define and contribute these definitions, especially during development.

PX4 includes the mavlink/mavlink repo as a submodule under /src/modules/mavlink, containing XML definition files in /mavlink/messages/1.0/. This is a great resource for anyone looking to dive deeper into MAVLink definitions.

The build toolchain generates the MAVLink 2 C header files at build time, and you can define the XML file for which header files are generated in the PX4 kconfig board configuration. There are two ways to do this:

The generated files are then built into the mavlink module by default, and you can search for menuconfig MAVLINK_DIALECT in src/modules/mavlink/Kconfig to see the available options.