core: always send heartbeat on serial connections

src/mavsdk/core/mavsdk_impl.cpp

@@ -532,6 +532,15 @@ ConnectionResult MavsdkImpl::add_serial_connection(
     if (ret == ConnectionResult::Success) {
         add_connection(new_conn);
     }
+
+    auto new_configuration = get_configuration();
+
+    // PX4 starting with v1.13 does not send heartbeats by default, so we need
+    // to initiate the MAVLink connection by sending heartbeats.
+    // Therefore, we override the default here and enable sending heartbeats.
+    new_configuration.set_always_send_heartbeats(true);
+    set_configuration(new_configuration);
+
     return ret;
 }
 
@@ -541,6 +550,11 @@ void MavsdkImpl::add_connection(const std::shared_ptr<Connection>& new_connectio
     _connections.push_back(new_connection);
 }
 
+Mavsdk::Configuration MavsdkImpl::get_configuration() const
+{
+    return _configuration;
+}
+
 void MavsdkImpl::set_configuration(Mavsdk::Configuration new_configuration)
 {
     // We just point the default to the newly created component. This means

src/mavsdk/core/mavsdk_impl.h

@@ -68,6 +68,7 @@ class MavsdkImpl {
     std::vector<std::shared_ptr<System>> systems() const;
 
     void set_configuration(Mavsdk::Configuration new_configuration);
+    Mavsdk::Configuration get_configuration() const;
 
     uint8_t get_own_system_id() const;
     uint8_t get_own_component_id() const;