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MAVLink Peripherals (GCS/OSD/Gimbal/Camera/Companion) ​

Ground Control Stations (GCS), On-Screen Displays (OSD), MAVLink Cameras & Gimbals, Remote IDs, Companion Computers, ADS-B receivers, and other MAVLink peripherals interact with PX4 using separate MAVLink streams, sent via different serial ports.

In order to configure that a particular serial port is used for MAVLink traffic with a particular peripheral, we use Serial Port Configuration, assigning one of the abstract "MAVLink instance" configuration parameters to the desired port. We then set other properties of the MAVLink channel using the parameters associated with our selected MAVLink instance, so that they match the requirements of our particular peripheral.

The most relevant parameters are described below (the full set are listed in the Parameter Reference > MAVLink).

In order to assign a particular peripheral to a serial port we use the concept of a MAVLink instance.

Each MAVLink instance represents a particular MAVLink configuration that you can apply to a particular port. At time of writing three MAVLink instances are defined, each represented by a parameter MAV_X_CONFIG, where X is 0, 1, 2.

Each instance has associated parameters that you can use to define the properties of the instance on that port, such as the set of streamed messages (see MAV_X_MODE below), data rate (MAV_X_RATE), whether incoming traffic is forwarded to other MAVLink instances (MAV_X_FORWARD), and so on.

INFO

MAVLink instances are an abstract concept for a particular MAVLink configuration. The number in the name means nothing; you can assign any instance to any port.

The parameters for each instance are:

  • MAV_X_CONFIG - Set the serial port (UART) for this instance "X", where X is 0, 1, 2. It can be any unused port, e.g.: TELEM2, TELEM3, GPS2 etc. For more information see Serial Port Configuration.
  • MAV_X_MODE - Specify the MAVLink profile for the instance, such as Normal or OSD. Profiles define a particular set of streamed messages and their rates — you should choose a profile that is appropriate for your channel and the peripheral.
  • MAV_X_RATE - Set the maximum data rate for this instance (bytes/second).
    • This is the combined rate for all streams of individual message (the rates for individual messages are reduced if the total rate exceeds this value).
    • The default setting will generally be acceptable, but might be reduced if the telemetry link becomes saturated and too many messages are being dropped.
    • A value of 0 sets the data rate to half the theoretical value.
  • MAV_X_FORWARD - Enable forwarding of MAVLink packets received by the current instance onto other interfaces. This might be used, for example, to transfer messages between a GCS and a companion computer so that the GCS can talk to a MAVLink enabled camera connected to the companion computer.

Next you need to set the baud rate for the serial port you assigned above (in MAV_X_CONFIG).

TIP

You will need to reboot PX4 to make the parameter available (i.e. in QGroundControl).

The parameter used will depend on the assigned serial port - for example: SER_GPS1_BAUD, SER_TEL2_BAUD, etc. The value you use will depend on the type of connection and the capabilities of the connected MAVLink peripheral.

Default MAVLink Ports ​

TELEM1 ​

The TELEM 1 port is almost always configured by default for the GCS telemetry stream ("Normal").

To support this there is a default serial port mapping of MAVLink instance 0 as shown below:

TELEM2 ​

The TELEM 2 port usually configured by default for a companion computer telemetry stream ("Onboard").

To support this there is a default serial port mapping of MAVLink instance 0 as shown below:

ETHERNET ​

Pixhawk 5x devices (and later) that have an Ethernet port, configure it by default to connect to a GCS:

On this hardware, there is a default serial port mapping of MAVLink instance 2 as shown below:

For more information see: PX4 Ethernet Setup

Device Specific Setup ​

Links to setup instructions for specific MAVLink components:

另见 ​