MavLink is a communication protocol for MAV (Micro Aerial Vehicles) that has nowadays been extended to all kind of drones (both aerial and terrestrial).
The MAVLink message is basically a stream of bytes encoded and sent over some kind of transductor (via USB serial, RC frequencies, WiFi, GPRS, etc.). By encoding we mean to put the packet into a data structure in a smart way adding checksums, sequence numbers and send it via the channel byte by byte.
Each MAVLink message is structured in the following way:
message length = 17 bytes (6 bytes header + 9 bytes payload + 2 bytes checksum)
The following table describes the message parts and bytes:
| Message part | Byte | Description |
|---|---|---|
| Header | 0 | message header, always 0xFE |
| Header | 1 | Message length |
| Header | 2 | Sequence number, rolls from 0 to 255 |
| Header | 3 | System ID, This is the source (i.e. Mission planner) sending a message. The software does a regular check so as to know that this message is for itself. |
| Header | 4 | Component ID, what component of the system is sending the message |
| Header | 5 | Message ID (e.g. 0 = heartbeat). What is this message about. |
| Payload | 6 | Variable sized payload specified by the byte |
| Payload | 7 - 14 | Variable sized payload specified by the byte |
| Checksum | 15 - 16 | Checksum |