added simple flight termination state machine which enbales parachute on request

src/modules/commander/commander.cpp

@@ -509,6 +509,21 @@ void handle_command(struct vehicle_status_s *status, const struct safety_s *safe
 		}
 		break;
 
+	/* Flight termination */
+	case VEHICLE_CMD_DO_SET_SERVO: { //xxx: needs its own mavlink command
+
+			if (armed->armed && cmd->param3 > 0.5) { //xxx: for safety only for now, param3 is unused by VEHICLE_CMD_DO_SET_SERVO
+				transition_result_t flighttermination_res = flighttermination_state_transition(status, FLIGHTTERMINATION_STATE_ON, control_mode);
+				result = VEHICLE_CMD_RESULT_ACCEPTED;
+
+			} else {
+				/* reject parachute depoyment not armed */
+				result = VEHICLE_CMD_RESULT_TEMPORARILY_REJECTED;
+			}
+
+		}
+		break;
+
 	default:
 		break;
 	}
@@ -1199,6 +1214,7 @@ int commander_thread_main(int argc, char *argv[])
 		bool arming_state_changed = check_arming_state_changed();
 		bool main_state_changed = check_main_state_changed();
 		bool navigation_state_changed = check_navigation_state_changed();
+		bool flighttermination_state_changed = check_flighttermination_state_changed();
 
 		hrt_abstime t1 = hrt_absolute_time();
 
@@ -1725,7 +1741,8 @@ void *commander_low_prio_loop(void *arg)
 		/* ignore commands the high-prio loop handles */
 		if (cmd.command == VEHICLE_CMD_DO_SET_MODE ||
 		    cmd.command == VEHICLE_CMD_COMPONENT_ARM_DISARM ||
-		    cmd.command == VEHICLE_CMD_NAV_TAKEOFF)
+		    cmd.command == VEHICLE_CMD_NAV_TAKEOFF ||
+		    cmd.command == VEHICLE_CMD_DO_SET_SERVO)
 			continue;
 
 		/* only handle low-priority commands here */

src/modules/commander/state_machine_helper.cpp

@@ -65,6 +65,7 @@ static const int ERROR = -1;
 static bool arming_state_changed = true;
 static bool main_state_changed = true;
 static bool navigation_state_changed = true;
+static bool flighttermination_state_changed = true;
 
 transition_result_t
 arming_state_transition(struct vehicle_status_s *status, const struct safety_s *safety,
@@ -451,6 +452,18 @@ check_navigation_state_changed()
 	}
 }
 
+bool
+check_flighttermination_state_changed()
+{
+	if (flighttermination_state_changed) {
+		flighttermination_state_changed = false;
+		return true;
+
+	} else {
+		return false;
+	}
+}
+
 void
 set_navigation_state_changed()
 {
@@ -523,6 +536,44 @@ int hil_state_transition(hil_state_t new_state, int status_pub, struct vehicle_s
 }
 
 
+/**
+* Transition from one flightermination state to another
+*/
+transition_result_t flighttermination_state_transition(struct vehicle_status_s *status, flighttermination_state_t new_flighttermination_state, struct vehicle_control_mode_s *control_mode)
+{
+	transition_result_t ret = TRANSITION_DENIED;
+
+		/* only check transition if the new state is actually different from the current one */
+		if (new_flighttermination_state == status->navigation_state) {
+			ret = TRANSITION_NOT_CHANGED;
+
+		} else {
+
+			switch (new_flighttermination_state) {
+			case FLIGHTTERMINATION_STATE_ON:
+				ret = TRANSITION_CHANGED;
+				status->flighttermination_state = FLIGHTTERMINATION_STATE_ON;
+				warnx("state machine helper: change to FLIGHTTERMINATION_STATE_ON");
+				break;
+			case FLIGHTTERMINATION_STATE_OFF:
+				ret = TRANSITION_CHANGED;
+				status->flighttermination_state = FLIGHTTERMINATION_STATE_OFF;
+				break;
+
+			default:
+				break;
+			}
+
+			if (ret == TRANSITION_CHANGED) {
+				flighttermination_state_changed = true;
+				control_mode->flag_control_flighttermination_enabled = status->flighttermination_state == FLIGHTTERMINATION_STATE_ON;
+			}
+		}
+
+		return ret;
+}
+
+
 
 // /*
 //  * Wrapper functions (to be used in the commander), all functions assume lock on current_status

src/modules/commander/state_machine_helper.h

@@ -70,8 +70,12 @@ bool check_main_state_changed();
 
 transition_result_t navigation_state_transition(struct vehicle_status_s *status, navigation_state_t new_navigation_state, struct vehicle_control_mode_s *control_mode);
 
+transition_result_t flighttermination_state_transition(struct vehicle_status_s *status, flighttermination_state_t new_flighttermination_state, struct vehicle_control_mode_s *control_mode);
+
 bool check_navigation_state_changed();
 
+bool check_flighttermination_state_changed();
+
 void set_navigation_state_changed();
 
 int hil_state_transition(hil_state_t new_state, int status_pub, struct vehicle_status_s *current_state, int control_mode_pub, struct vehicle_control_mode_s *current_control_mode, const int mavlink_fd);