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Mavlink

MAVLink is used as the messaging layer between the main parts of a UAV system. It carries telemetry, commands, mission data, parameters, status updates, and sensor information over serial links, UDP/TCP, radios, or onboard networks.

The main MAVLink components are:

  • Autopilot / flight controller: controls the vehicle and publishes telemetry.
  • Ground control station (GCS): monitors the vehicle and sends commands or mission plans.
  • Companion computer: runs higher-level software such as computer vision, autonomy, or payload control.
  • MAVLink router or bridge: forwards MAVLink traffic between links, tools, and components.

pymavlink

wireshark and network debug tools

mavlink network

MAVLink has been deployed in a number of versions:

  • MAVLink 1: 0xFE
  • MAVLink 2: 0xFD

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SYSID (System ID)

A number that identifies the vehicle/system. (1-255) Distinguishes different vehicles on the same MAVLink network (Vehicle ID)

Examples:

  • Drone #1 → SYSID = 1
  • Drone #2 → SYSID = 2
  • Simulator (SITL) → often SYSID = 1 (configurable)
  • GCS () = 255

COMPID (Component ID)

A number that identifies a component inside a system. (1-255) Distinguishes subsystems within the same vehicle

Think of it as the process/module ID

Common COMPIDs: - 1 → Autopilot (flight controller) - 190 → Companion computer - 191 → GCS (ground control station) - 200+ → Custom components

Source / Target / Broadcast

MAVLink separates the sender identity from any optional receiver target:

  1. Message header → source

Every MAVLink frame contains the sender IDs in the header:

  • sysid / source_system - the system that sent the message
  • compid / source_component - the component that sent the message

These identify who sent the message. They are normally set by the MAVLink library or connection configuration.

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  1. Payload fields → target

Only some MAVLink messages are addressed to a receiver. Those messages include target fields in the payload, for example:

  • target_system
  • target_component

These identify who should handle or execute the message. Common examples are command, mission, and parameter messages.

Example: COMMAND_LONG(76)

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Broadcast

For messages that have target fields, 0 means broadcast:

1
2
target_system    = 0
target_component = 0
  • target_system = 0 - send to all systems
  • target_component = 0 - send to all components in the selected system

Telemetry messages usually do not have target fields. They are simply published by the sender, and any MAVLink peer on the link may consume them.

Avoid broadcasting control commands unless the intended behavior is clear and safe.