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Core LEGO MINDSTORMS Programming: Unleash the Power of the Java Platform

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Core LEGO MINDSTORMS Programming: Unleash the Power of the Java Platform


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  • Copyright 2002
  • Dimensions: K
  • Pages: 560
  • Edition: 1st
  • Book
  • ISBN-10: 0-13-009364-5
  • ISBN-13: 978-0-13-009364-6

  • Complete 3-D plans for building five unique robots
  • Advanced control techniques—including distance and compass sensors
  • Behavior control programming, the breakthrough methodology invented at MIT
  • For LEGO Mindstorms Robotics Invention System, versions 1.0, 1.5, and 2.0

Your LEGO Mindstorms robots can do more than you ever imagined. The secret: go beyond the built-in tools, and leverage the power of the Java platform—the world's hottest programming technology.

Core LEGO Mindstorms shows you how, step by step. Working from beautifully rendered 3-D plans, you'll construct five unique robots-each capable of increasingly powerful navigation. You'll build and program two powerful custom sensors-an accurate distance sensor and the "Holy Grail" of navigation sensors: the compass sensor.

Brian Bagnall, co-creator of the leJOS Java Virtual Machine for LEGO Mindstorms, starts with the absolute basics then teaches you sophisticated, never-before-published techniques for controlling LEGO Mindstorms robots. No matter what version of LEGO Mindstorms you own, this book will teach you how to build robots with remarkable intelligence and amazing power.

  • Installing leJOS, the Java Virtual Machine designed for the LEGO Mindstorms RCX programmable controller
  • Setting up your Java platform development environment for LEGO Mindstorms
  • Programming rotation and custom sensors
  • Using behavior control programming, the biologically inspired MIT breakthrough in robot control
  • New techniques for improving navigation accuracy
  • Gathering map data and transmitting it back to your computer
  • For LEGO Mindstorms RIS versions 1.0, 1.5, and 2.0—including USB versions



For your convenience, you can download the complete set of code examples from the book in a compressed archive. The code is available in three compression formats:

Code Examples .zip
Code Examples .tgz
Code Examples .sea.hqx

Sample Content

Online Sample Chapters

Lego Mindstorms Programming: RCX Communications

Navigation in LEGO MINDSTORMS Programming

Table of Contents




Enter MINDSTORMS. The Robotics Invention System. RCX Brick. IR Tower. Motors. Sensors. LEGO Parts. Building Tippy. The RIS CD Software. The World of MINDSTORMS. ROBOLAB(tm). LogIT Sensors. Technic. Robotics Discovery Set. Vision Command. RIS Expansion Sets. Code Pilot. Droid Developer Kit. Dark Side Developer Kit. CyberMaster. Ultimate Accessory Kit. Ultimate Builders Set.

2. Getting Started with leJOS.

leJOS Overview. JVM. RCX Platform Extensions. Java API. Robotics Programming. Installing leJOS. Windows 98/Windows Me. Windows NT/Windows 2000. Linux. Macintosh OSX. Testing leJOS. Creating and Running a Program. Uploading More Than One Program. Setting Up an IDE. JCreator (Windows Platforms). How leJOS “Stacks Up”. NQC. PbFORTH. LegOS. Visual Basic. leJOS vs. TinyVM.

3. Learn Java in 2.4 Hours!

Java Core Language. OOP. Source Files. Classes. Interfaces. Import and Package Statements. Methods. Overloading Methods. Fields and Variables. Naming Rules. Operators. Program Flow Control. The java.lang Package. Math. Object. Runtime. String. StringBuffer. System. Threads. Throwable. java.util. BitSet. Hashtable. Random. Vector.


josx.platform.rcx. Button. LCD. MinLCD. Motor. ROM. Sensor. Serial. Sound. MinSound. TextLCD. The josx.util Package. Timer. josx.robotics. java.io and josx.platform.rcx.comm..

5. LEGO 101.

RIS Parts Library. Bricks. Classic LEGO Bricks. Technic Beams. Specialized Bricks. Slope Bricks. Plates Overview. Rectangular Plates. Plates Overview. Specialty Plates. Pins. Tires, Wheel Hubs, and Treads. Axles. Axle Accessories. Gears. Pulleys. Pulley Drive Belts. Lift Arms. Other Parts. Common LEGO Structures. Chassis. Caster Wheels. Ratchets. Single Motor Navigation. Walking Mechanism. Building Philosophy 101.

6. Behavior Control.

Behavior Control Theory. Programming Behavior with leJOS. The Behavior API. Advanced Behavior Coding. Coding Foolproof takeControl() Methods. Coding Solid action() and suppress() Methods.

7. Navigation.

Understanding the Problem of Navigation. Navigation Theory. Trigonometry. Using the Navigator API. Creating a Navigator Robot. Building the Trilobot. Programming Trilobot. TimingNavigator Accuracy. Systematic Errors. Nonsystematic Errors. Summary.

8. Navigation with Rotation Sensors.

Understanding Rotation Sensors. Trailer Odometer. Handheld Odometer. On-Axle Odometers. Off-Axle Odometers. Angle Measurement. Using the RotationNavigator Class. Creating a Navigator Robot. Building Instructions. Programming Tippy Senior. RotationNavigator Accuracy. Systematic Errors. Nonsystematic Errors.

9. Proximity Detection.

Creating a Simple Proximity Sensor. Programming the Sensor. Reliability. Creating a Distance Sensor. The Sharp GP2D12 Sensor. A Primer in Electronics. Building the Distance Sensor. Permanent Assembly. Enclosing the Circuit. Programming the Proximity Sensor Driver. A Wall Follower.

10. Navigation with a Compass Sensor.

The Compass Sensor. Theory of Calculating Direction. Building the Compass Interface. Tools. Circuit Assembly. Testing the Circuit. Programming the Compass Class. Calibration. Compass Driver. Programming CompassNavigator. A Robot Using the Compass. Chassis. Compass Basket. Front Bumper. Final Assembly. Compass Accuracy.

11. RCX Communications.

The Communications API. InputStream. DataInputStream. DataOutputStream. DataPort. PCDataPort. RCXDataPort. Installation. IDE Setup. Uploading Map Data. Controlling the RCX Through a Network. Controlling the RCX from a Web Page. Installing a Web Server. A Simple Project. Alternate Data Transfer Methods. Alternate Communication Uses.

12. Advanced leJOS Topics.

Memory Issues. Monitoring Memory Use. Programming Efficient Code. Hacking leJOS to Save Memory. Performance Tips. Alternate Languages for the JVM. Using NetRexx on the RCX. leJOS Architecture Overview. The Firmware. The API. The Linker. Modifying and Recompiling the Firmware. Adding Native Methods. Portability of leJOS.

Appendix A. Parts and Kits.

LEGO Shop At Home. Pitsco LEGO Dacta. LogIT Sensors. Mindsensors.

Appendix B. Electronics Projects.

Electronics Sources. Europe. North America. International. Distance Sensor Parts. Europe. North America. Compass Sensor Parts. Europe. North America. Compass Sensor Circuit Building. Experimentor Board. Punchboard. Etched PC Board.

Appendix C. Utilities.

leJOS Binaries. lejosc.exe. lejos.exe. lejosfirmdl.exe. lejosrun.exe. emu-lejos.exe. emu-lejosrun.exe. lejosp.exe. lejosp1.exe. lejosc1.exe. emu-dump.exe. leJOS Utilities. RCX Direct-Mode. RCX Download. Bricks Music Studio. Text to LCD Display. leJOS Visual Interface. LEGO Utilities. Ldraw. MLCAD. L3P. LEO Cad.

Appendix D. Internet Resources.

leJOS Resources. leJOS Home Page. leJOS Project Development Home Page. Java Resources. Sun's Official Java Site. LEGO Resources. LEGO Users Group (LUGNet). RCX Resources. RCX Internals. Analysis of the RCX. Sensors and Actuators. Distance Sensor. Compass Sensor. Homebrew RCX Sensors. Resistor Color Bands. RCX Projects. Rubik's Cube Solver (and More). LEGO Robotics Network. Robot Navigation. Mobile Robot Positioning. Dead Reckoning Contest. Other Hardware. Tower Hobbies. Draganfly.




There are 718 LEGO pieces in the latest version of the Robotics Invention System. Depending on how you look at it, 718 can either seem like a large number or a small number. In the grand scheme of things, 718 seems like a small number to me. Of those pieces, 129 are unique LEGO parts (not including color differences). Looking around me, I'd say the Robotics Invention System can build a decent representation of just about everything in this room. It can build a desk, a chair, a primitive speaker, a spinning globe, a blender, a clock (digital or analog), or probably even a simulation of a CD player. Outside my domain, the kit could produce models of automobiles, subway cars, boats, or almost any man-made machine. Looking to nature, it could create simulations of spiders, ants, scorpions, dogs, cats, and whales. True, the kit by itself can't reproduce everything in the world. It can't reproduce the envelope of a helium balloon or a complete BMW assembly line, but the things it can't do are far outweighed by the things it can. And there are probably things it can build that no one has ever thought of! I'm going to go out on a limb and estimate that 718 pieces can create an infinite number of models. From this logic, it's easy to see that 718 equals infinity.

It's no exaggeration to say that LEGO MINDSTORMS has done for robots what Henry Ford did for automobiles. LEGO has managed to put robots in the hands of ordinary people. The standardized parts and common languages means sharing of ideas in robotics is happening on a scale that has never occurred before. A brief search of the web to shows just how much MINDSTORMS has permeated through cyberspace.

If you already own the Robotics Invention System, congratulations! You have almost everything you need to create some amazing robots. The only remaining tool you need is a truly powerful programming language, and that is what this book will present to you. The language is Java, one of the most universally accepted programming languages in computers today, and this book will show how to use Java to push MINDSTORMS to the limit.

This book is not a compilation of projects, (of which there are several good ones on the market). The aim of this book it to give you the knowledge and tools you need to turn your ideas into reality, not someone elses. All the projects in this book are presented because they have some sort of lasting value. If this book has done its job, hopefully you will be surprised by what you didn't know MINDSTORMS could do.

This book will also solve the greatest mystery of the MINDSTORMS kit-what the grey foot-pedal looking part is for (see Figure below). To my know-ledge, no one has yet discovered what this part does or how it is used. Not even the actual LEGO MINDSTORMS engineers who designed the part understand what it is for. Chapter 5 will answer this age old mystery.

About this Book

Chapter 1 is an introduction to the Robotics Invention System. This chapter covers just the main components of the kit, including software, the RCX brick, and the IR tower. It also introduces other kits and products that can expand your MINDSTORMS universe.

Chapter 2 is a basic introduction to leJOS, the Java platform for the RCX brick. It covers a bit of background on leJOS, the basic features that distinguish it from other RCX development tools, and instructions on how to install leJOS as well as a powerful IDE.

Chapter 3 is a high-speed introduction to Java. Those who are familiar with Java may opt to just skim the Notes and Warnings, which point out differences between leJOS Java and Sun's Java.

Chapter 4 demonstrates, through code examples, how to access motors, sensors, and other components of the RCX brick using Java.

Chapter 5 is an encyclopedia of the Robotics Invention System parts. It goes through each of the 129 unique parts of the kit so you can put a name to the part and identify all the uses. If you ever wondered what the other versions of the kit contained, this is where you can find out. There is also a section on common LEGO structures that will help you to rapidly build key structures.

Chapter 6 introduces the concept of Behavior Control programming, a technique of programming insect level, behavior based intelligence. The leJOS API contains several classes for programming your own behavior control, making this an easy and powerful addition to robotics programming.

Chapter 7 begins the concept of navigation. The first part of the chapter lays out the fundamental concepts of navigation and tries to impress upon the reader a true understanding of just what it is about navigation that makes it so difficult for robots. It then moves on to real world examples of navigation programming using leJOS.

Chapter 8 continues the topic of navigation, but this time using a pair of rotation sensors to achieve even more accurate navigation than possible with timing methods.

Chapter 9 presents unique ways of detecting objects before the robot collides with them. The first part of the chapter shows how to build a simple proximity detector using only the pieces contained in the kit. More ambitious MINDSTORMS users can build an accurate distance sensor from raw electronic components. I have endeavored to make the instructions for assembly as clear, simple and precise as possible so even those completely unfamiliar with electronics will be able build this powerful sensor. The last part of this chapter shows how to build a classic robot project, the wall follower.

Chapter 10 is the third and final chapter dealing with navigation. This chapter shows how to assemble a compass sensor, which is useful for determining the orientation of the robot using the earths magnetic field. Though more difficult than the proximity sensor, this sensor worked the very first time I plugged the components into the bread board, so most readers shouldn't encounter any problems with this project.

Chapter 11 introduces the topic of communications. The RCX is capable of communicating with other devices that use Infrared signals. This includes the PC, the LEGO Remote Control, and other RCX bricks. The powerful java.io API is available on the leJOS platform, making communications with a PC that much easier. This chapter also shows how to control the RCX brick from a PC across the Internet using a remote program, an embedded applet, or from a plain old web page.

Chapter 12, the final chapter of the book, covers advanced topics. Here you can learn everything you never wanted to know about leJOS. Since memory is always on the mind of an RCX programmer, this chapter describes memory saving strategies that can help you squeeze that last little bit of code on board the RCX. Another interesting aspect of the leJOS JVM is that Java is not the only language that it can execute! The leJOS JVM is also capable of running other languages, such as Forth, NetRexx, and dozens of others. There is also a writeup on how to port leJOS to other processors, something for only the most advanced users.

The appendices will give you some valuable information on leJOS and the RCX. There is a section on ordering sensors, kits, and other parts you may not even have known existed. Ordering electronics parts can be such an art-form that an entire Appendix is dedicated to this topic. There is also a section on the burgeoning utilities available for leJOS. Finally, no book on LEGO MINDSTORMS would be complete without a section of web resources.

Companion Web Site

This book has a companion Web site to provide you with updates and other material. It is located at www.phptr.com/bagnall



Below you will find updates and errata corrections.

Chapter 1

  • Pages 7-8. The RIS 1.5 does not contain an RCX 1.5 brick. It contains an RCX 1.0 brick without an A/C adapter port.
  • Page 53. Brake mode uses little or no battery power. The technical explanation is as follows: The motors are accessed via H-bridge. Braking the motor is accomplished by a short-circuit between both motor pins. (You can test this with a motor.) The braking effect is produced through the attempt of turning the motor-axle. The motor generates an electro-motive force with an opposite sign to the axle-motion. So, the only power consumption consists of what is added to the motor-axle and not from the power-supply. (Explanation courtesy of Claude Baumann.)
  • Page 54. The Prgm button selects the program, not View.

Chapter 2

Page 80. legOS currently allows floating point operations.

Chapter 7

  • Page 235. A loop needs to be added to the end of the main() method: for(;;);
  • Page 236: A loop needs to be added to the end of the main() method of both programs on this page: for(;;);

Chapter 8

Pages 280-281. The code for robots that use Navigator classes is highly interchangeable, however since Trilobot uses two bumper sensors and Tippy Senior uses only one sensor, the code must be altered slightly. To fix this, remove the LeftBump and RightBump objects, then replace them with a single Bump class that uses input S2 instead of S1 and S3.

Chapter 11

  • Some changes have been made to the leJOS communications API:
    • josx.platform.rcx.comm has been changed to josx.rcxcomm.
    • pc.irtower.comm has been changed to josx.rcxcomm.
    • RCXDataPort and PCDataPort have both been changed to RCXPort.
    • The RCXPort() constructor throws an IOException.
    • For specific changes, please see the source code for Chapter 11.
  • Pages 425 to 426. You do not have to install the Javacomm API. The new version of leJOS contains native methods to handle communications with the USB and Serial ports. The PC side JAR file must be placed in the classpath, however. Please consult the leJOS readme for full leJOS Comm API installation instructions.

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