AP_OpenDroneID: prevent sending of lost transmitter msg too fast

libraries/AP_OpenDroneID/AP_OpenDroneID.cpp

@@ -171,7 +171,8 @@ void AP_OpenDroneID::send_static_out()
     const uint32_t now_ms = AP_HAL::millis();
 
     // we need to notify user if we lost the transmitter
-    if (now_ms - last_arm_status_ms > 5000) {
+    if (now_ms - last_arm_status_ms > 5000 && now_ms - last_lost_tx_ms > 5000) {
+        last_lost_tx_ms = now_ms;
         GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "ODID: lost transmitter");
     }
 

libraries/AP_OpenDroneID/AP_OpenDroneID.h

@@ -142,6 +142,9 @@ private:
     mavlink_open_drone_id_arm_status_t arm_status;
     uint32_t last_arm_status_ms;
 
+    // last time we sent a lost transmitter message
+    uint32_t last_lost_tx_ms;
+
     // transmit functions to manually send a static MAVLink message
     void send_dynamic_out();
     void send_static_out();