This document describes Robo4J, an open source framework for robotics programming in Java. Some key points: - Robo4J provides hardware abstractions and units to easily interface with hardware like Raspberry Pi GPIO, Lego Mindstorms, and more. - It uses a declarative configuration to define units and connections between units that represent hardware and robot behaviors. - Pre-built units handle common hardware like sensors, actuators, and communication protocols. Users can also define their own units. - The framework supports networking and autodiscovery to enable remote control of robots over the internet or local network.

1. http://robo4j.io
Robo4J
@robo4j
Robotics on Java Simplified
Robo4J
Marcus Hirt, Oracle
Miroslav Wengner, MAN Truck & Bus AG

2. http://robo4j.io
Robo4J
@robo4j
Robo4J
• Easy to use framework for quickly getting started writing Java
for hardware
• Pure Java framework
• Uses Pi4J for GPIO access
• Core components independently usable

3. http://robo4j.io
Robo4J
@robo4j
robo4j-hw-pi
Robo4J Overview
robo4j-math
robo4j-core
robo4j-hw-lego
My Robot
robo4j-units-pi
robo4j-units-lego
robo4j-http

4. http://robo4j.io
Robo4J
@robo4j
Robo4J Hardware Modules
• Simple to use Java abstractions for hardware
• Can be used stand alone, does not depend on anything
robo4j-hw-*

5. http://robo4j.io
Robo4J
@robo4j
Hardware Example
public class HelloLcd {
public static void main(String[] args) throws Exception {
AdafruitLcd lcd = LcdFactory.createLCD();
lcd.setBacklight(Color.TEAL);
lcd.setText("Hello World!n-----Robo4J-----");
}
}
Adafruit LCD

6. http://robo4j.io
Robo4J
@robo4j
Robo4J Core
• Defines the core abstractions
• A RoboBuilder builds the RoboContext which is basically a ”robot”
• A RoboContext contains RoboReferences to RoboUnits, which are agents to
which messages can be sent
• Annotations on RoboUnits can change on which queue messages are sent
• Provides network services (autodiscovery, remote messaging)
• Is plain old Java
robo4j-core

7. http://robo4j.io
Robo4J
@robo4j
Robo4J Hardware Specific Units
• Pre-packaged, configurable units
• Easy to use
• Typically configured using XML (or programmatically)
robo4j-units-*

8. http://robo4j.io
Robo4J
@robo4j
Robo4J Threading

9. http://robo4j.io
Robo4J
@robo4j
Robo4J Threading
2
2
10

10. http://robo4j.io
Robo4J
@robo4j
Typical Project
1. Add the units for your hardware to your configuration
2. Add your own units for controlling behaviour
3. Add a class with a main method where you initialize it all
through a RoboBuilder
4. Run the main method

11. http://robo4j.io
Robo4J
@robo4j
Example
public class LcdExampleDeclarativeMain {
public static void main(String[] args) throws RoboBuilderException, IOException {
RoboBuilder builder = new RoboBuilder().add(getResource("robo4j.xml"));
RoboContext ctx = builder.build();
ctx.start();
ctx.getReference("lcd").sendMessage(
new LcdMessage("Robo4J: Welcome!nPress Up/Down!"));
System.out.println("Press enter to quit!");
System.in.read();
ctx.shutdown();
}
…
}

12. http://robo4j.io
Robo4J
@robo4j
robo4j.xml
<robo4j>
<roboUnit id="lcd">
<class>com.robo4j.units.rpi.lcd.AdafruitLcdUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x20</value>
</config>
</roboUnit>
<roboUnit id="buttons">
<class>com.robo4j.units.rpi.lcd.AdafruitButtonUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int”>0x20</value>
<value name="target" type="String">controller</value>
</config>
</roboUnit>
<roboUnit id="controller">
<class>com.robo4j.rpi.lcd.example.controller.LcdExampleController</class>
<config name="com.robo4j.root">
<value name="target" type="String">lcd</value>
</config>
</roboUnit>
</robo4j>

13. http://robo4j.io
Robo4J
@robo4j
Controller
@CriticalSectionTrait
public class LcdExampleController extends RoboUnit<AdafruitButtonEnum> {
…
public void onMessage(AdafruitButtonEnum message) {
if (!isDemoRunning()) {
processAdafruitMessage(message);
} else {
SimpleLoggingUtil.print(getClass(), "Skipping " + message + " due to test already running!");
}
}
public void onInitialization(Configuration configuration) throws ConfigurationException {
target = configuration.getString("target", null);
if (target == null) {
throw ConfigurationException.createMissingConfigNameException("target");
}
}
…

14. http://robo4j.io
Robo4J
@robo4j
Controller, continued
…
private void processAdafruitMessage(AdafruitButtonEnum myMessage) {
switch (myMessage) {
case DOWN:
moveToNextDemo();
break;
case UP:
moveToPreviousDemo();
break;
case SELECT:
runDemo();
break;
default:
sendLcdMessage(getContext(), String.format("Button %snis not in use...", myMessage));
}
}
}

15. http://robo4j.io
Robo4J
@robo4j
Adafruit LCD Demo

16. http://robo4j.io
Robo4J
@robo4j
Example – Robotic Arm

17. http://robo4j.io
Robo4J
@robo4j
Robotic Arm Demo

18. http://robo4j.io
Robo4J
@robo4j
Robo4J Networking
• Autodiscovery / Heartbeats / Native package format
• Messaging / Remote Contexts

19. http://robo4j.io
Robo4J
@robo4j
Autodiscovery Enablement
<robo4j>
<roboSystem>
<config name="com.robo4j.root">
<value name="poolSizeScheduler" type="int">2</value>
…
<config name="com.robo4j.messageServer">
<value name="port" type="int">0</value>
</config>
<config name="com.robo4j.discovery">
<value name="multicastAddress" type="String">238.12.15.254</value>
<value name="port" type="int">0x0FFE</value>
<value name="heartBeatInterval" type="int">250</value>
<value name="enabled" type="boolean">true</value>
<config name="com.robo4j.discovery.metadata">
<value name="name" type="String">Button Activator</value>
<value name="description" type="String">Little remote controlled button</value>
</config>
</config>
</config>
</roboSystem>
</robo4j>

20. http://robo4j.io
Robo4J
@robo4j
Remote Messaging
String id = "myid";
LookupService lookupService =
LookupServiceProvider.getDefaultLookupService();
RoboContext context = lookupService.getContext(id);
RoboReference<String> reference = context.getReference(id);
reference.sendMessage("Hello!");

21. http://robo4j.io
Robo4J
@robo4j
Lookup by Metadata
Stream<RoboContextDescriptor> matchingDescriptors =
lookupService.getDiscoveredContexts().values().stream().
filter((ctx) -> isRoboticOverlord(ctx));
…
private static boolean isRoboticOverlord(RoboContextDescriptor context) {
return context.getMetadata().containsKey("isRoboticOverlord");
}

22. http://robo4j.io
Robo4J
@robo4j
Button Presser Demo
with Autodiscovery

23. http://robo4j.io
Robo4J
@robo4j
Robo4J Http Communication
• Want to communicate messages to the units over http
• Simply add HttpServerUnit or HttpClientUnit
• Communication is implemented using Java NIO
• Messages by default sent as Json
• Translate from/to Json and the message type accepted by the unit
• Define your codecs: @HttpProducer, @HttpDecoder, @HttpEncoder

24. http://robo4j.io
Robo4J
@robo4j
Robo4J REST
• Default get operation is listing all registered units with their states
• Default post operation for a unit is to send a message to it
• There must be a registered http codec for converting from Json to
the message type for the message to be received
HTTP GET: http://<ROBO4J_IP>:<ROBO4J_PORT>
HTTP POST: http://<ROBO4J_IP>:<ROBO4J_PORT>/units/<unit id>

25. http://robo4j.io
Robo4J
@robo4j
Robo4J Example Get
HTTP GET : http://127.0.0.1:8025
uid: 142d7167-7a43-477e-8dfd-75fdd711b6da,
response: [
{
id:"controller",
com.robo4j.LifecycleState:"STARTED“
},
{
id:"httpServer",
com.robo4j.LifecycleState:"STOPPED"
},
...
]

26. http://robo4j.io
Robo4J
@robo4j
Robo4J Example Post
Example: http://localhost:8025/units/controller
BODY:
{“message”: “push“}
Returns HTTP code 202, if message was deserialized properly and
put on the bus. Returns 404 if unit is not found. Returns 501 if, for
example, no codec is present for the type required by the unit.

27. http://robo4j.io
Robo4J
@robo4j
Video Streaming Demo Configuration
<robo4j>
<roboUnit id="httpClient">
<class>com.robo4j.socket.http.units.HttpClientUnit</class>
<config name="com.robo4j.root">
<value name="address" type="String">SERVER_IP</value>
<value name="port" type="int">SERVER_PORT</value>
<value name="mode" type="boolean">true</value>
<value name="targetUnits" type="String">{"imageController":"POST"}</value>
</config>
</roboUnit>
<roboUnit id="imageController">
<class>com.robo4j.units.rpi.camera.RaspistillUnit</class>
<config name="com.robo4j.root">
<value name="targetOut" type="String">httpClient</value>
<value name="client" type="String">SERVER_IP</value>
<value name="clientPort" type="String">SERVER_PORT</value>
<value name="clientUri" type="String”>/<SERVER_ENDPOINT></value>
<value name="width" type="String">320</value>
<value name="height" type="String">240</value>
<value name="timelapse" type="String">100</value>
</config>
</roboUnit>
</robo4j>
• Two Robo4J Systems
• Robo4J on JavaFx

28. http://robo4j.io
Robo4J
@robo4j
Video and Image Streaming Demo
with Autodiscovery

29. http://robo4j.io
Robo4J
@robo4j
Robo4J and Lego
Robo4J supports LejOS 9.x on Java 8 and above
Hardware abstractions in robo4j-hw-lego
Units in robo4j-units-lego
Robo4J allows you to mix Lego functionality with other hardware
Turn On the robot named “Number42”

30. http://robo4j.io
Robo4J
@robo4j
Lego Robot Number42 is alive
<robo4j>
<roboUnit id="http">
<class>com.robo4j.socket.http.units.HttpServerUnit</class>
<config name="com.robo4j.root">
<value name="port" type="int">8025</value>
<value name="target" type="String">controller</value>
<value name="packages" type="String">com.robo4j.lego.j1kids.example.codec</value>
<value name="targetUnits" type="String">{"controller":"GET"}</value>
</config>
</roboUnit>
<roboUnit id="buttons">
<class>com.robo4j.units.lego.BrickButtonsUnit</class>
<config name="com.robo4j.root">
<value name="target" type="String">controller</value>
<value name="button_right" type="String">left</value>
<value name="button_left" type="String">right</value>
<value name="button_up" type="String">down</value>
<value name="button_down" type="String">up</value>
<value name="button_enter" type="String">enter</value>
</config>
</roboUnit>
<roboUnit id="lcd">
<class>com.robo4j.units.lego.LcdUnit</class>
<config name="com.robo4j.root">
</config>
</roboUnit>
<roboUnit id="controller">
<class>com.robo4j.lego.j1kids.example.controller.PlatformController</class>
<config name="com.robo4j.root">
<value name="target" type="String">platform</value>
</config>
</roboUnit>
<roboUnit id="weaponController">
<class>com.robo4j.lego.j1kids.example.controller.WeaponController</class>
<config name="com.robo4j.root">
<value name="target" type="String">weapon</value>
</config>
</roboUnit>
<roboUnit id="touchUnit">
<class>com.robo4j.units.lego.TouchUnit</class>
<config name="com.robo4j.root">
<value name="target" type="String">weaponController</value>
</config>
</roboUnit>
<roboUnit id="weapon">
<class>com.robo4j.units.lego.SingleMotorUnit</class>
<config name="com.robo4j.root">
</config>
</roboUnit>
<roboUnit id="platform">
<class>com.robo4j.units.lego.SimpleTankUnit</class>
<config name="com.robo4j.root">
<value name="leftMotorPort" type="String">B</value>
<value name="leftMotorType" type="Character">N</value>
<value name="rightMotorPort" type="String">C</value>
<value name="rightMotorType" type="Character">N</value>
</config>
</roboUnit>
</robo4j>

31. http://robo4j.io
Robo4J
@robo4j
Lego Demo

32. http://robo4j.io
Robo4J
@robo4j
Coff-E
• Robotic platform (Wall-E on Java)
• 3D printed + Makeblock + Pololu + Adafruit hardware

33. http://robo4j.io
Robo4J
@robo4j

34. http://robo4j.io
Robo4J
@robo4j
Coff-E at JavaOne 2016
The embedded video on this page was removed due to presentation size restrictions.
We’ve uploaded the embedded video on youtube here:
https://www.youtube.com/watch?v=cNLlPGiBzqg

35. http://robo4j.io
Robo4J
@robo4j
Configuration
<robo4j>
<roboUnit id="lcd">
<class>com.robo4j.units.rpi.lcd.AdafruitLcdUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x20</value>
</config>
</roboUnit>
<roboUnit id="buttons">
<class>com.robo4j.units.rpi.lcd.AdafruitButtonUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x20</value>
<value name="target" type="String">controller</value>
</config>
</roboUnit>
<robo4j>
<roboUnit id="motion">
<class>com.robo4j.units.rpi.roboclaw.RoboClawRCTankUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x40</value>
<value name="leftChannel" type="int">6</value>
<value name="rightChannel" type="int">7</value>
</config>
</roboUnit>
</robo4j>
<roboUnit id="laserscanner.servo">
<class>com.robo4j.units.rpi.pwm.PCA9685ServoUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x40</value>
<value name="channel" type="int">0</value>
<value name="trim" type="float">7</value>
<value name="shutdownValue" type="float">0</value>
</config>
</roboUnit>
<roboUnit id="laserscanner.tilt">
<class>com.robo4j.units.rpi.pwm.PCA9685ServoUnit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x40</value>
<value name="channel" type="int">1</value>
<value name="trim" type="float">-40</value>
<value name="inverted" type="boolean">true</value>
<value name="shutdownValue" type="float">0</value>
</config>
</roboUnit>
<roboUnit id="scanner">
<class>com.robo4j.units.rpi.lidarlite.LaserScanner</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x62</value>
<value name="servo" type="String">laserscanner.servo</value>
<value name="servoRange" type="float">45.0</value>
<value name="angularSpeed" type="float">100.0</value>
<value name="minAquisitionTime" type="float">2.5</value>
<value name="trim" type="float">5.5</value>
</config>
</roboUnit>
<roboUnit id="gyro">
<class>com.robo4j.units.rpi.gyro.GyroL3GD20Unit</class>
<config name="com.robo4j.root">
<value name="bus" type="int">1</value>
<value name="address" type="int">0x6b</value>
<value name="sensitivity" type="String">DPS_245</value>
<value name="enableHighPass" type="boolean">true</value>
<value name="period" type="int">10</value>
</config>
</roboUnit>
<roboUnit id="tank">
<class>com.robo4j.coffe.controllers.TankController</class>
<config name="com.robo4j.root">
<value name="useTracks" type="boolean">false</value>
<value name="maxSpeed" type="float">0.4</value>
</config>
</roboUnit>
<roboUnit id="scanprocessor">
<class>com.robo4j.coffe.units.ScanProcessor</class>
</roboUnit>
<roboUnit id="missioncontroller">
<class>com.robo4j.coffe.controllers.MissionController</class>
<config name="com.robo4j.root">
<value name="lcd" type="String">lcd</value>
<value name="tank" type="String">tank</value>
<value name="scanner" type="String">scanner</value>
<value name="scanProcessor" type="String">scanprocessor</value>
<value name="modeOfOperation" type="String">fastest_path</value>
</config>
</roboUnit>
.
. (GPS, magnetometer etc.)
.
</robo4j>

36. http://robo4j.io
Robo4J
@robo4j
Build Your Own Coff-E
• See Thingiverse for more information:
https://www.thingiverse.com/thing:1730244
• See the robo4j-coffe repo for code

37. http://robo4j.io
Robo4J
@robo4j
Tools Demo
JDK Mission Control Plug-in (JFR, LIDAR Scan Visualization)
Magnetometer Calibration Utility (MagViz)

38. http://robo4j.io
Robo4J
@robo4j
Summary
• Robots are fun
• Java and Robo4J lets you build them quickly
• We have just started
(had a bit of a break the past year getting/tending to
babies/toddlers)…
• …but hopefully this helps someone
• Please give us feedback!
Also build a robot. You will not regret it! :)

39. http://robo4j.io
Robo4J
@robo4j
For More Info
Robo4J Homepage: http://www.robo4j.io
Robo4J on Twitter: @robo4j
Marcus on Twitter: @hirt
Miro on Twitter: @miragemiko