Add Traffic Avoidance System (ADSB/FLARM) Arming Check (#26390)

* Add traffic avoidance system checks

* Update msg/px4_msgs_old/msg/VehicleStatusV1.msg

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>

* docs: add arming check for traffic avoidance systems in ADS-B/FLARM documentation

* fix formating

* trafficAvoidanceCheck: switch case for configuration options

---------

Co-authored-by: Hamish Willee <hamishwillee@gmail.com>
Co-authored-by: Matthias Grob <maetugr@gmail.com>

src/lib/events/enums.json

@@ -276,6 +276,10 @@
                         "1073741824": {
                             "name": "open_drone_id",
                             "description": "Open Drone ID system"
+                        },
+                        "2147483648": {
+                            "name": "traffic_avoidance",
+                            "description": "Traffic Avoidance (ADSB/FLARM)"
                         }
                     }
                 },

src/modules/commander/Commander.cpp

@@ -2880,6 +2880,22 @@ void Commander::dataLinkCheck()
 				_vehicle_status.open_drone_id_system_present = true;
 				_vehicle_status.open_drone_id_system_healthy = healthy;
 			}
+
+			// Traffic avoidance system (ADSB or FLARM)
+			if (telemetry.heartbeat_type_adsb || telemetry.heartbeat_type_flarm) {
+				if (_traffic_avoidance_system_lost) { // recovered
+					_traffic_avoidance_system_lost = false;
+
+					if (_datalink_last_heartbeat_traffic_avoidance_system != 0) {
+						mavlink_log_info(&_mavlink_log_pub, "Traffic avoidance system regained\t");
+						events::send(events::ID("commander_traffic_avoidance_regained"), events::Log::Info,
+							     "Traffic avoidance system regained");
+					}
+				}
+
+				_datalink_last_heartbeat_traffic_avoidance_system = telemetry.timestamp;
+				_vehicle_status.traffic_avoidance_system_present = true;
+			}
 		}
 	}
 
@@ -2931,6 +2947,16 @@ void Commander::dataLinkCheck()
 		_open_drone_id_system_lost = true;
 		_status_changed = true;
 	}
+
+	// Traffic avoidance system (ADSB/FLARM)
+	if ((hrt_elapsed_time(&_datalink_last_heartbeat_traffic_avoidance_system) > 3_s)
+	    && !_traffic_avoidance_system_lost) {
+		mavlink_log_critical(&_mavlink_log_pub, "Traffic avoidance system lost");
+		events::send(events::ID("commander_traffic_avoidance_lost"), events::Log::Critical, "Traffic avoidance system lost");
+		_vehicle_status.traffic_avoidance_system_present = false;
+		_traffic_avoidance_system_lost = true;
+		_status_changed = true;
+	}
 }
 
 void Commander::battery_status_check()

src/modules/commander/Commander.hpp

@@ -243,6 +243,7 @@ private:
 	hrt_abstime _datalink_last_heartbeat_gcs{0};
 	hrt_abstime _datalink_last_heartbeat_onboard_controller{0};
 	hrt_abstime _datalink_last_heartbeat_parachute_system{0};
+	hrt_abstime _datalink_last_heartbeat_traffic_avoidance_system{0};
 
 	hrt_abstime _last_print_mode_reject_time{0};	///< To remember when last notification was sent
 
@@ -268,6 +269,7 @@ private:
 	bool _open_drone_id_system_lost{true};
 	bool _onboard_controller_lost{false};
 	bool _parachute_system_lost{true};
+	bool _traffic_avoidance_system_lost{true};
 
 	bool _last_overload{false};
 	bool _mode_switch_mapped{false};

src/modules/commander/HealthAndArmingChecks/CMakeLists.txt

@@ -65,6 +65,7 @@ px4_add_library(health_and_arming_checks
 	checks/rcCalibrationCheck.cpp
 	checks/sdcardCheck.cpp
 	checks/systemCheck.cpp
+	checks/trafficAvoidanceCheck.cpp
 	checks/vtolCheck.cpp
 	checks/windCheck.cpp
 

src/modules/commander/HealthAndArmingChecks/HealthAndArmingChecks.hpp

@@ -72,6 +72,7 @@
 #include "checks/vtolCheck.hpp"
 #include "checks/offboardCheck.hpp"
 #include "checks/openDroneIDCheck.hpp"
+#include "checks/trafficAvoidanceCheck.hpp"
 #include "checks/externalChecks.hpp"
 
 class HealthAndArmingChecks : public ModuleParams
@@ -157,6 +158,7 @@ private:
 	RcAndDataLinkChecks _rc_and_data_link_checks;
 	VtolChecks _vtol_checks;
 	OffboardChecks _offboard_checks;
+	TrafficAvoidanceChecks _traffic_avoidance_checks;
 #ifndef CONSTRAINED_FLASH
 	ExternalChecks _external_checks;
 #endif
@@ -197,5 +199,6 @@ private:
 		&_flight_time_checks,
 		&_rc_and_data_link_checks,
 		&_vtol_checks,
+		&_traffic_avoidance_checks,
 	};
 };

src/modules/commander/HealthAndArmingChecks/checks/trafficAvoidanceCheck.cpp

@@ -0,0 +1,71 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2026 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include "trafficAvoidanceCheck.hpp"
+
+
+void TrafficAvoidanceChecks::checkAndReport(const Context &context, Report &reporter)
+{
+	NavModes affected_modes{NavModes::None}; // COM_ARM_TRAFF 1 - warning only, arming allowed, affected_modes stays None
+
+	switch (_param_com_arm_traff.get()) {
+	case 0:
+		return; // Check disabled
+
+	case 2:
+		affected_modes = NavModes::All; // Disallow arming for all modes
+		break;
+
+	case 3:
+		affected_modes = NavModes::Mission; // Disallow arming for mission
+		break;
+	}
+
+	if (!context.status().traffic_avoidance_system_present) {
+		/* EVENT
+		 * @description
+		 * Traffic avoidance system (ADSB/FLARM) failed to report. Make sure it is setup and connected properly.
+		 *
+		 * <profile name="dev">
+		 * This check can be configured via <param>COM_ARM_TRAFF</param> parameter.
+		 * </profile>
+		 */
+		reporter.armingCheckFailure(affected_modes, health_component_t::traffic_avoidance,
+					    events::ID("check_traffic_avoidance_missing"),
+					    events::Log::Error, "Traffic avoidance system missing");
+
+		if (reporter.mavlink_log_pub()) {
+			mavlink_log_critical(reporter.mavlink_log_pub(), "Preflight Fail: Traffic avoidance system missing");
+		}
+	}
+}

src/modules/commander/HealthAndArmingChecks/checks/trafficAvoidanceCheck.hpp

@@ -0,0 +1,50 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2026 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#pragma once
+
+#include "../Common.hpp"
+
+class TrafficAvoidanceChecks : public HealthAndArmingCheckBase
+{
+public:
+	TrafficAvoidanceChecks() = default;
+	~TrafficAvoidanceChecks() = default;
+
+	void checkAndReport(const Context &context, Report &reporter) override;
+
+private:
+	DEFINE_PARAMETERS_CUSTOM_PARENT(HealthAndArmingCheckBase,
+					(ParamInt<px4::params::COM_ARM_TRAFF>) _param_com_arm_traff
+				       )
+};

src/modules/commander/commander_params.c

@@ -836,6 +836,21 @@ PARAM_DEFINE_INT32(COM_ARM_HFLT_CHK, 1);
  */
 PARAM_DEFINE_INT32(COM_ARM_ODID, 0);
 
+/**
+ * Enable Traffic Avoidance system detection check
+ *
+ * This check detects if a traffic avoidance system (ADSB/FLARM transponder)
+ * is missing. Depending on the value of the parameter, the check can be
+ * disabled, warn only, or deny arming.
+ *
+ * @group Commander
+ * @value 0 Disabled
+ * @value 1 Warning only
+ * @value 2 Enforce for all modes
+ * @value 3 Enforce for mission modes only
+ */
+PARAM_DEFINE_INT32(COM_ARM_TRAFF, 0);
+
 /**
  * Enforced delay between arming and further navigation
  *

src/modules/mavlink/mavlink_receiver.cpp

@@ -2177,6 +2177,10 @@ MavlinkReceiver::handle_message_heartbeat(mavlink_message_t *msg)
 				_heartbeat_type_adsb = now;
 				break;
 
+			case MAV_TYPE_FLARM:
+				_heartbeat_type_flarm = now;
+				break;
+
 			case MAV_TYPE_CAMERA:
 				_heartbeat_type_camera = now;
 				camera_status.timestamp = now;
@@ -2925,6 +2929,7 @@ void MavlinkReceiver::CheckHeartbeats(const hrt_abstime &t, bool force)
 		tstatus.heartbeat_type_onboard_controller      = (t <= TIMEOUT + _heartbeat_type_onboard_controller);
 		tstatus.heartbeat_type_gimbal                  = (t <= TIMEOUT + _heartbeat_type_gimbal);
 		tstatus.heartbeat_type_adsb                    = (t <= TIMEOUT + _heartbeat_type_adsb);
+		tstatus.heartbeat_type_flarm                   = (t <= TIMEOUT + _heartbeat_type_flarm);
 		tstatus.heartbeat_type_camera                  = (t <= TIMEOUT + _heartbeat_type_camera);
 		tstatus.heartbeat_type_parachute               = (t <= TIMEOUT + _heartbeat_type_parachute);
 		tstatus.heartbeat_type_open_drone_id           = (t <= TIMEOUT + _heartbeat_type_open_drone_id);

src/modules/mavlink/mavlink_receiver.h

@@ -391,6 +391,7 @@ private:
 	hrt_abstime _heartbeat_type_onboard_controller{0};
 	hrt_abstime _heartbeat_type_gimbal{0};
 	hrt_abstime _heartbeat_type_adsb{0};
+	hrt_abstime _heartbeat_type_flarm{0};
 	hrt_abstime _heartbeat_type_camera{0};
 	hrt_abstime _heartbeat_type_parachute{0};
 	hrt_abstime _heartbeat_type_open_drone_id{0};