MAVLink C UDP Example

The MAVLink UDP Example is a simple C example that sends some data to QGroundControl using MAVLink over UDP. QGroundControl responds with heartbeats and other messages, which are then printed by this program.

The example should work on any Unix-like system (Linux, MacOS, BSD, etc.). These instructions were tested on a clean Ubuntu LTS 20.04 installation using the default version of gcc (9.3.0).

Building/Running the Example

The following instructions show how to build and run the example.

1. Install MAVLink and generate the MAVLink 2.0 libraries into the mavlink/include directory. For example, to generate the headers for common.xml you could use the command line:

   python3 -m pymavlink.tools.mavgen --lang=C --wire-protocol=2.0 --output=./include/ message_definitions/v1.0/common.xml
   

   Alternatively you can clone the mavlink/mavlink repository and Download prebuilt headers to the same location.

The example will not work with MAVLink 1 because it uses a message that includes extension fields which do not exist in MAVLink 1 (SYS_STATUS).

You can put/generate the library wherever you like, but the build command below assumes they are located in directory named include below the MAVLink root directory.

1. Open a terminal and navigate to examples/linux

2. Compile with GCC using the following command:

   gcc -std=c99 -I ../../include/common -o mavlink_udp mavlink_udp.c
   

   The MAVLink header directory must be added to the include path. The path here assumes you are building the code from the example directory, and that have installed the headers in mavlink/include.

3. Run the executable from the terminal:

   ./mavlink_udp
   

   By default, the example will listen for data on the localhost IP address, port 14551. You can specify another IP address as a command line argument (use ./mavlink_udp --help to see usage).

4. Open QGroundControl on the same machine.

   QGroundControl immediately starts broadcasting its HEARTBEAT on port 14551.

   QGroundControl returns data, but will not actually "connect" to the example (it will continue to display the message Waiting for Vehicle Connection).

5. The example should start displaying the received data in the terminal:

   ~/github/mavlink/examples/linux$ ./mavlink_udp
   Bytes Received: 17
   Datagram: fe 09 00 ff 00 00 00 00 00 00 06 08 c0 04 03 19 87 
   Received packet: SYS: 255, COMP: 0, LEN: 9, MSG ID: 0
   
    Bytes Received: 17
   Datagram: fe 09 01 ff 00 00 00 00 00 00 06 08 c0 04 03 f3 f9 
   Received packet: SYS: 255, COMP: 0, LEN: 9, MSG ID: 0
   
   ...