QGC Guide (master)

Ports (PX4) ​

The Ports page assigns functions such as MAVLink telemetry, GPS and RC input to the vehicle's serial ports, and to Ethernet on boards that have it.

PX4 stores this per function: each function has a parameter (for example MAV_0_CONFIG or GPS_1_CONFIG) that selects the port it runs on. This page shows the same settings with one row per port. It is only shown for PX4 builds that have serial port functions, so it does not appear for SITL.

Port Rows ​

Each row shows:

  • Port — the port name used by the flight controller, such as TELEM 1 or GPS 1. Below the name are the parameters that put a function on the port, for example GPS_1_CONFIG = 201. The dot next to the name is green when a function is on the port, and orange when the port needs a reboot or has a conflict.
  • Function — what runs on the port. The functions normally used on that kind of port are listed first. Any function can run on any serial port, so the list also includes the others.
  • Baud — the port's baud rate (SER_<port>_BAUD). Ethernet has no baud rate.
  • Options — extra settings for the selected function: mode, send rate, forwarding and flow control for MAVLink, and protocol for GPS. A send rate (MAV_<n>_RATE) of 0 makes PX4 use half the link's bandwidth: baud rate / 20 bytes/s, or 100000 bytes/s over Ethernet.

Selecting a function for a serial port removes any other function from that port. Several functions can use Ethernet at the same time, so the Ethernet row shows a switch for each one instead.

The page opens on In Use when any port has a function, showing only the ports that have a function or a change waiting for a reboot. Select All Ports to show every port.

Loading... is shown while QGroundControl reads a setting that the vehicle did not send in its parameter list. PX4 only sends a port's baud rate and options once a function is using them.

If more than one function is assigned to the same serial port, the row shows a warning: only one of them will start.

PX4 always starts the RC Input Driver. Setting it to Disabled does not stop it: it then uses the board's default RC port. So the RC Input Driver stays on the Radio Controller port until it is assigned to another port: that port has no None choice meanwhile, and another function assigned there is shown as a conflict.

Applying Changes ​

Changes are written to the vehicle immediately, but all of these settings only take effect after the vehicle reboots. Changed rows are marked Reboot required, and a banner at the top of the page offers:

  • Reboot Vehicle — reboot to apply the changes (not available while armed).
  • Revert Changes — write back the values the settings had when the page was opened.

Both buttons are disabled until the vehicle has acknowledged every change, so a slow link can't apply only part of one.