Added check how many MAVSDK systems are available.

src/az_config.h

@@ -1,5 +1,6 @@
 #pragma once
 
+// Please check the port name! Also baudrates must match or devices can't communicate with each other.
 const char *AZ_CONNECTION_SERIAL     = "serial:///dev/ttyS0:115200";
 const char *AZ_CONNECTION_UDP        = "udp://:14550";
 const int AZ_RELATIVE_FLY_ALTITUDE   = 50;

src/az_drone_controller.cpp

@@ -73,6 +73,14 @@ bool AzDroneController::stateConnect(void)
 
 bool AzDroneController::stateAutopilot(void)
 {
+    std::vector<std::shared_ptr<System>> systems = mMavsdk.systems();
+    qDebug() << "AzDroneController::stateAutopilot() Found" << systems.size() << "systems";
+
+    if (systems.size() == 0) {
+        std::cerr << "No system found." << std::endl;
+        return 1;
+    }
+
     std::optional<std::shared_ptr<System>> autopilot = mMavsdk.first_autopilot(AZ_GET_AUTOPILOT_TIMEOUT);
 
     if (autopilot.has_value()) {