Hello,
I’m hitting an error with the Telemetry plugin that I can’t seem to make my way through. It looks similar to the issue here, but the solution to that issue is no longer applicable since one only needs to link the MAVSDK::mavsdk library to the final executable for current versions of MAVSDK.
Essentially, when I compile my code, I receive a linking error back that states: “undefined reference to `mavsdk::Telemetry::Telemetry(mavsdk::Telemetry const&)’”
My CMakeLists file contains the following information:
cmake_minimum_required(VERSION 3.8)
project(uavrt_connection)
find_package(MAVSDK REQUIRED)
include_directories(include)
# ClassA.so
add_library(ClassA SHARED
src/ClassA.cpp)
ament_target_dependencies(ClassA
MAVSDK)
# ClassB.so
add_library(ClassB SHARED
src/ClassB.cpp)
ament_target_dependencies(ClassB
MAVSDK)
add_executable(main
src/main.cpp)
target_link_libraries(main
MAVSDK::mavsdk)
install(TARGETS
ClassA
ClassB
ARCHIVE DESTINATION lib
LIBRARY DESTINATION lib
RUNTIME DESTINATION bin)
install(TARGETS
main
DESTINATION lib/${PROJECT_NAME})
A bare-bones example of the code where the error occurs:
ClassA.cpp
// C++ standard library headers
#include <chrono>
#include <functional>
#include <memory>
#include <thread>
namespace example
{
ClassA::ClassA()
{
mavsdk.add_udp_connection("udp://:14540");
while (mavsdk.systems().size() == 0)
{
std::this_thread::sleep_for(std::chrono::seconds(1));
}
GetSystem();
TelemetryCallback();
}
void ClassA::GetSystem() : ClassBObject()
{
if (mavsdk.systems().size() == 1)
{
system_ = serial_mavsdk.systems().at(0);
connection_status_ = true;
}
}
void ClassA::TelemetryCallback()
{
if (connection_status_ == true)
{
mavsdk::Telemetry mavsdk_telemetry = mavsdk::Telemetry(system_);
ClassBObject.RefreshTelemetry(mavsdk_telemetry); // <--- This line causes the error.
}
}
} // namespace example
ClassA.hpp
// MAVSDK header files
#include "mavsdk/mavsdk.h"
#include "mavsdk/system.h"
#include "mavsdk/plugins/telemetry/telemetry.h"
namespace example
{
class ClassA
{
public:
private:
GetSystem();
TelemetryCallback();
mavsdk::Mavsdk mavsdk;
std::shared_ptr<mavsdk::System> system_;
bool connection_status_;
ClassB ClassBObject;
};
} // namespace example
The public function “RefreshTelemetry(mavsdk_telemetry)” is within a separate ClassB.cpp and ClassB.hpp file. The structure is similar to ClassA.cpp and ClassA.hpp and contains the same include statements. It is linked in the CMakeLists file the same way that ClassA is linked.
The repo that houses this code is currently private, so I can’t link it directly. If the example code I provided above is lacking, please let me know.
Two things that stood out while debugging:
- If I change
mavsdk::Telemetry mavsdk_telemetry = mavsdk::Telemetry(system_);tostd::shared_ptr<mavsdk::Telemetry> mavsdk_telemetry = std::make_shared<mavsdk::Telemetry>(system_);(and the corresponding function headers in ClassA and ClassB), then the code will compile. However, when I run it and attempt to retrieve values, all I get back are nan values. I’ve ran the code example code here and I did not have issues retrieving altitude values with a Px4 gazebo SITL. - If I remove this line
ClassBObject.RefreshTelemetry(mavsdk_telemetry);, then I am able to compile. Again, if I make the change in the previous bullet, then this line doesn’t to be removed and I can compile.
The compiling is being done on a Ubuntu 20.04 LTS machine using gcc version 9.4.0 and CMake version 3.16.3.
I appreciate any help,
Matt