caoqing32/ros_nodes

Ros communication interface for dart

Library template made by Stagehand under a BSD-style license.

Usage

A simple subscriber example:

import 'package:ros_nodes/messages/std_msgs/String.dart';
import 'package:ros_nodes/ros_nodes.dart';

void main() async {
  var config = RosConfig(
    'ros_nodes_example_node',
    'http://192.168.1.12:11311/',
    '192.168.1.12',
    24125,
  );
  var client = RosClient(config);
  var msg = StdMsgsString();
  var topic = RosTopic('chatter', msg);
  await client.unsubscribe(topic);

  var subscriber = await client.subscribe(topic);
  subscriber.onValueUpdate.listen((type) => print('Listener 1: ${type.data}'));
  subscriber.onValueUpdate.listen((_) => print('Listener 2: ${msg.data}'));
}

onValueUpdate is broadcast Stream. This stream emmits suppplied RosMessage as stream parameter, so we don't need to save it as a variable.

subscriber.onValueUpdate.listen((type) => print('Listener 1: ${type.data}'));
subscriber.onValueUpdate.listen((_) => print('Listener 2: ${msg.data}'));

It's important to say, that supplied RosMessage object, here StdMsgsString, is used as container for all data changes, both for publishing and getting data from other nodes. That's why both listeners will print the same data, both approaches are consider valid.

A simple publisher example:

import 'dart:async';
import 'package:ros_nodes/messages/std_msgs/String.dart';
import 'package:ros_nodes/ros_nodes.dart';

void main() async {
  var config = RosConfig(
    'ros_nodes_example_node',
    'http://192.168.1.12:11311/',
    '192.168.1.12',
    24125,
  );
  var client = RosClient(config);
  var topic = RosTopic('chatter', StdMsgsString());
  await client.unregister(topic);

  var publisher = await client.register(topic,
      publishInterval: Duration(milliseconds: 1000));

  var i = 0;
  Timer.periodic(
    Duration(milliseconds: 500),
    (_) {
      i += 1;
      topic.msg.data = i.toString();
    },
  );
}

By default RosPublisher will send updates every second. To change the interval you need to supply publishInterval parameter.

var i = 0;
Timer.periodic(
  Duration(milliseconds: 500),
  (_) {
    i += 1;
    topic.msg.data = i.toString();
  },
);

To change the published data we operate on supplied RosMessage type, in this case it's StdMsgsString.

All currently implemented messages are placed in lib/messages, where direct .dart files are wrappers for base type messages like RosString in String.dart file, and subfolders are meant for published messages like tf/tfMessage.dart as TfTfMessage or std_msgs/String.dart for aforementioned StdMsgsString.

Features and bugs

Please file feature requests and bugs at the issue tracker.