C++ Examples

Information about writing example code is covered in the Contributing > Writing Plugins (plugin developers should initially create integration tests rather than examples for new code).

This section contains examples showing how to use Dronecode SDK.

Example Description
Takeoff and Land Shows basic usage of the SDK (connect to port, detect system (vehicle), arm, takeoff, land, get telemetry)
Fly Mission Shows how to create, upload, and run missions.
Fly QGC Plan Mission Fly a mission imported from a QGroundControl mission plan.
Offboard Velocity Control Demonstrates how to control a vehicle in Offboard mode using velocity commands (in both the NED and body frames).
Follow Me Mode Demonstrates how to put vehicle in Follow Me Mode and set the current target position and relative position of the drone.
VTOL Transitions Shows how to transition a VTOL vehicle between copter and fixed-wing modes.

The examples are "largely" built and run in the same way, as described in the following section (any exceptions are covered in the page for the associated example).

Some of the examples define flight behaviour relative to the default home position in the simulator (e.g. Fly Mission). Care should be taken if using them on a real vehicle.

Trying the Examples

The easiest way to test the examples is to use a simulated PX4 vehicle that is running on the same computer. First start PX4 in SITL (Simulation), optionally start QGroundControl to observe the vehicle, then build and run the example code.

The simulator broadcasts to the standard PX4 UDP port for connecting to offboard APIs (14540). The examples connect to this port using either add_any_connection() or add_udp_connection().

Setting up a Simulator

PX4 supports a number of simulators. In order to set up the jMAVSim or Gazebo simulator, you can simply follow the standard PX4 toolchain setup instructions for macOS or Ubuntu Linux.

JMAVSim can only be used to simulate multicopters. Gazebo additionally supports a number of other vehicles (e.g. VTOL, Rovers, fixed-wing etc.).

After running a standard installation, a simulation can be started from the PX4 /Firmware directory using the command:

  • Multicopter (jMAVSim): make posix_sitl_default jmavsim
  • Multicopter (Gazebo): make posix_sitl_default gazebo
  • VTOL (Gazebo): make posix_sitl_default gazebo_standard_vtol

Using QGroundControl

You can use QGroundControl to connect to PX4 and observe vehicle movement and behaviour while the examples are running. QGroundControl will automatically connect to the PX4 simulation as soon as it is started.

See QGroundControl > Download and Install for information about setting up QGroundControl on your platform.

Building the Examples

To build the examples follow the instructions below, replacing takeoff_and_land with the name of the specific example. Any exceptions will be covered in the page for the associated example(s).

Linux

First Build and install the SDK C++ Library system-wide using the command below:

make clean
make default
sudo make default install

Then build the example:

cd example/takeoff_land/
mkdir build && cd build
cmake ..
make

Windows

First Build and install the SDK C++ Library. Make sure that you install the library and headers locally in the standard location:

cmake --build . --target install

Modify the example as described in Building C++ Apps > SDK Installed Locally (this is required for Windows).

Build the example as described in Building C++ Apps. Below we show how for the takeoff_land example, but all the other examples are built in the same way:

cd example/takeoff_land/
mkdir build && cd build
cmake .. -G "Visual Studio 15 2017 Win64"
cmake --build .

The debug binary for the example is stored under \Debug folder.

Running the Examples

You can then run the example, specifying the connection URL as the first argument. When running with the Simulator, you will use the connection string: udp://:14540

On Linux/macOS you would run the following (from the /build directory):

./takeoff_and_land udp://:14540

For Windows you would run the following (from the \build\Debug\ directory):

.\Debug\takeoff_and_land.exe udp://:14540

Most examples will create a binary with the same name as the example. The name that is used is specified in the CMakeLists.txt file as the first value in the call to add_executable().

If you have already started the simulation the example code should connect to PX4, and you will be able to observe behaviour through the SDK terminal, SITL terminal, and/or QGroundControl.

Troubleshooting

Linux: Error loading shared libraries

The following error is raised when you run an application/example on Linux and the Dronecode SDK shared library cannot be found:

error while loading shared libraries: libdronecode_sdk.so: cannot open shared object file: No such file or directory

The solution is to update the linker cache so that the system can find the library. On Ubuntu call the following:

sudo ldconfig

For more information/other Linux flavours see Linux Documentation > Shared Libraries.

© Dronecode 2017. License: CC BY 4.0            Updated: 2018-11-07 01:25:57

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