1. LeJOS Java for Lego RCX CJ Chung Associate Professor of Computer Science Director of Robofest Assistants Maurice Tedder Steven Kryskalla Rick Dudley

2. Agenda 9:00 am - Introduction to LeJos Java Programming using Eclipse
9:15 am – Installation of Java, Eclipse, and LeJos
9:45 am – LeJOS Java Programming Workshop
11:00 am – Mini Challenge
11:45 am - Wrap-up

3. Why Autonomous Robots?

5. 2 Million Dollar Prize, 2005
142 Miles, within 10 hours

6. Weaponized robot, also known as SWORDS in Iraq, Jan. 14, 2005
Many of the vehicles being developed will have some autonomy, meaning they'll navigate rough terrain, avoid obstacles and make decisions about certain tasks on their own
The Pentagon's research arm, the Defense Advanced Research Projects Agency, also recently awarded contracts to aid research of robots that one day could be dropped into combat from airplanes

7. Your RJ (Roverbot Jr.) Two motors One light sensor on input port no. 1
Left A
Right C
One light sensor on input port no. 1
One touch sensor on input port no. 2
One brain: H8 microprocessor, 16MHz

8. Why Java to program the Brain?

9. Why Java? AP CS A and AB using Java since 03-04 year
Write Once, Run Anywhere
AP CS A and AB using Java since year
Pure OO (Object Oriented) language
Standardized
Free

11. Characteristics of Java
Simple: automatic memory allocation and garbage collection. # of language Construct is small.
Portable
Robust (Reliable): “exception handling”
Multithreaded
Interpreted
Distributed
Secure
Architecture Neutral
Dynamic: You can freely add methods in a class at runtime)

12. LeJOS for Lego LeJOS [Ley-J-oss] http://lejos.sourceforge.net
Replacement Firmware for Lego RCX brick – JVM for RCX
Size: 16KB
around 12 KB for user-programs
Download for Free
Can be thought of as J2ME (Java 2 Micro Edition) for smaller devices such as pagers, cell phones, and handheld PCs.
Total Memsize of RCX: 16KB for ROM

13. LeJos Memory Map User Programs (12 KB) Routines for ROM (4 KB)
leJos JVM
(16 KB)
ROM
(16 KB)

14. Advantages of using Java for Lego instead of NQC (or C++)
Pure Object Oriented. Enormous APIs
Floating point numbers: vital for navigation
Recursion
Threads
Simple Event Model
You can use custom made sensors, easily
Powerful networking APIs
Web control of your robot
Everything is for free
However, no Garbage collection yet (?)
Trigonometric functions

15. Comparing RCX programming languages
RCX code
leJos
NQC (VB)
LegOS
pbForth
Language
Graphical
Java
NQC
C/C++
Forth
FW replacement
N/A
Yes No
Floating-point
Programmable Display
Trig and adv math
Interpreted

16. How to Install LeJos programming environment
Using DOS
Start | Control Panel | System | Advanced | Environment Variables
Add c:\lejos\bin to the system PATH, if leJos was installed at c:\lejos
IDE
Eclipse: the best free Java tool
resources button

17. Uploading JVM to RCX using DOS
Fast mode: lejosfirmdl –f
Slow mode: lejosfirmdl
It takes about one minutes
After the download, you should see a number on the LCD representing the battery voltage

18. Compile, Upload, and Run using DOS
Compile: lejosc <filename>.java
Upload: lejos <filename>
Press the green button
Uploading more than one program
lejos <filename>,<filename>
Program 0
Program 1

19. Workshop Topics Eclipse programming environment
Learning Java Basics with Lego RCX
Repetition – while and for
Decision – if, if else
Methods
Variables
Sensors
IR Packet Communications
Mini Challenge: a part of Robofest Challenge, RoboRelay

20. Robofest 2005 Junior Division (5-9th) Senior Division (9th-12th)
Exhibition Division
13 regional competitions
Top winning teams to World Robofest at LTU on April 23.
MPC laptops to the best team for each division

21. Class Mission 1 Do forever
Beep when the light sensor sees the bright light

22. Class Mission 2
Go forward until the robot detects the edge of the white board. Stop at the edge of the board

23. Class Mission 3
Go forward while counting N black lines. Stop right after the Nth black line

24. Mini Challenge (a part of Robofest Game)
Start when the lamp under the board is on
Follow the black line until it detects the end of the line (edge detection)
Turn around
Coming back to the home base
Stop when the bumper (touch senor) is hit