uxrce_dds: support multi-instance uORB topics

Enable DDS bridge to handle multi-instance uORB topics by mapping
multiple topic instances to a single DDS topic with instance field.

src/modules/uxrce_dds_client/dds_topics.h.em

@@ -162,8 +162,22 @@ struct RcvTopicsPubs {
 	uORB::Publication<@(sub['simple_base_type'])_s> @(sub['topic_simple'])_pub{ORB_ID(@(sub['topic_simple']))};
 @[    end for]@
 
-@[    for sub in subscriptions_multi]@
+@# Group subscriptions_multi by topic to create arrays
-	uORB::PublicationMulti<@(sub['simple_base_type'])_s> @(sub['topic_simple'])_pub{ORB_ID(@(sub['topic_simple']))};
+@{
+multi_topic_groups = {}
+for sub in subscriptions_multi:
+    topic_simple = sub['topic_simple']
+    if topic_simple not in multi_topic_groups:
+        multi_topic_groups[topic_simple] = []
+    multi_topic_groups[topic_simple].append(sub)
+}@
+@[    for topic_simple, subs in multi_topic_groups.items()]@
+	uORB::PublicationMulti<@(subs[0]['simple_base_type'])_s> @(topic_simple)_pubs[@(len(subs))] {
+@[        for idx, sub in enumerate(subs)]@
+		{ORB_ID(@(topic_simple))}@('' if idx == len(subs)-1 else ',')
+
+@[        end for]@
+	};
 @[    end for]@
 
 	uint32_t num_payload_received{};
@@ -179,7 +193,7 @@ static void on_topic_update(uxrSession *session, uxrObjectId object_id, uint16_t
 	pubs->num_payload_received += length;
 
 	switch (object_id.id) {
-@[    for idx, sub in enumerate(subscriptions + subscriptions_multi)]@
+@[    for idx, sub in enumerate(subscriptions)]@
 	case @(idx)+ (65535U / 32U) + 1: {
 			@(sub['simple_base_type'])_s data;
 
@@ -190,6 +204,18 @@ static void on_topic_update(uxrSession *session, uxrObjectId object_id, uint16_t
 		}
 		break;
 
+@[    end for]@
+@[    for idx, sub in enumerate(subscriptions_multi)]@
+	case @(idx + len(subscriptions))+ (65535U / 32U) + 1: {
+			@(sub['simple_base_type'])_s data;
+
+			if (ucdr_deserialize_@(sub['simple_base_type'])(*ub, data, time_offset_us)) {
+				//print_message(ORB_ID(@(sub['simple_base_type'])), data);
+				pubs->@(sub['topic_simple'])_pubs[@(sub['instance'])].publish(data);
+			}
+		}
+		break;
+
 @[    end for]@
 
 	default:
@@ -200,13 +226,20 @@ static void on_topic_update(uxrSession *session, uxrObjectId object_id, uint16_t
 
 bool RcvTopicsPubs::init(uxrSession *session, uxrStreamId reliable_out_stream_id, uxrStreamId reliable_in_stream_id, uxrStreamId best_effort_in_stream_id, uxrObjectId participant_id, const char *client_namespace)
 {
-@[    for idx, sub in enumerate(subscriptions + subscriptions_multi)]@
+@[    for idx, sub in enumerate(subscriptions)]@
 	{
 			uint16_t queue_depth = orb_get_queue_size(ORB_ID(@(sub['simple_base_type']))) * 2; // use a bit larger queue size than internal
 			uint32_t message_version = get_message_version<@(sub['simple_base_type'])_s>();
 			create_data_reader(session, reliable_out_stream_id, best_effort_in_stream_id, participant_id, @(idx), client_namespace, "@(sub['topic'])", message_version, "@(sub['dds_type'])", queue_depth);
 	}
 @[    end for]@
+@[    for idx, sub in enumerate(subscriptions_multi)]@
+	{
+			uint16_t queue_depth = orb_get_queue_size(ORB_ID(@(sub['topic_simple']))) * 2; // use a bit larger queue size than internal
+			uint32_t message_version = get_message_version<@(sub['simple_base_type'])_s>();
+			create_data_reader(session, reliable_out_stream_id, best_effort_in_stream_id, participant_id, @(idx + len(subscriptions)), client_namespace, "@(sub['topic'])", message_version, "@(sub['dds_type'])", queue_depth);
+	}
+@[    end for]@
 
 	uxr_set_topic_callback(session, on_topic_update, this);
 

src/modules/uxrce_dds_client/dds_topics.yaml

@@ -52,7 +52,7 @@ publications:
 
   - topic: /fmu/out/transponder_report
     type: px4_msgs::msg::TransponderReport
- 
+
   # - topic: /fmu/out/vehicle_angular_velocity
   #   type: px4_msgs::msg::VehicleAngularVelocity
 
@@ -191,7 +191,7 @@ subscriptions:
     type: px4_msgs::msg::ActuatorServos
 
   - topic: /fmu/in/aux_global_position
-    type: px4_msgs::msg::VehicleGlobalPosition
+    type: px4_msgs::msg::AuxGlobalPosition
 
   - topic: /fmu/in/fixed_wing_longitudinal_setpoint
     type: px4_msgs::msg::FixedWingLongitudinalSetpoint
@@ -228,3 +228,10 @@ subscriptions:
 
 # Create uORB::PublicationMulti
 subscriptions_multi:
+  - type: px4_msgs::msg::AuxGlobalPosition
+    uorb_topic: aux_global_position
+    ros_topics:
+      - /fmu/in/aux_global_position_A
+      - /fmu/in/aux_global_position_B
+      - /fmu/in/aux_global_position_C
+      - /fmu/in/aux_global_position_D

src/modules/uxrce_dds_client/generate_dds_topics.py

@@ -131,11 +131,30 @@ if subs_not_empty:
 merged_em_globals['subscriptions'] = msg_map['subscriptions'] if subs_not_empty else []
 
 subs_multi_not_empty = msg_map['subscriptions_multi'] is not None
+expanded_subs_multi = []
 if subs_multi_not_empty:
     for sm in msg_map['subscriptions_multi']:
-        process_message_type(sm)
+        if 'ros_topics' in sm and 'uorb_topic' in sm:
+            # Expand each DDS topic into a separate entry
+            # All entries for the same uorb_topic will use the same array
+            uorb_topic_name = sm['uorb_topic']
+            for idx, dds_topic in enumerate(sm['ros_topics']):
+                expanded_entry = {
+                    'type': sm['type'],
+                    'topic': dds_topic,
+                    'uorb_topic': uorb_topic_name,
+                    'instance': idx
+                }
+                process_message_type(expanded_entry)
+                expanded_entry['topic_simple'] = uorb_topic_name
+                expanded_subs_multi.append(expanded_entry)
+        else:
+            # Fallback for old-style single topic entries
+            process_message_type(sm)
+            sm['instance'] = 0
+            expanded_subs_multi.append(sm)
 
-merged_em_globals['subscriptions_multi'] = msg_map['subscriptions_multi'] if subs_multi_not_empty else []
+merged_em_globals['subscriptions_multi'] = expanded_subs_multi
 
 merged_em_globals['type_includes'] = sorted(set(all_type_includes))