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LEGO Mindstorms Robot and Java

LEGO Mindstorms Robot and Java. Fall 2004. http://marsrovers.jpl.nasa.gov/mission/spacecraft_surface_rover.html. Java as a Platform. Sun Microsystem has different Java sizes (virtual machines sizes) for devices with different capabilities Java 2 Enterprise Edition (J2EE) for big machines

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LEGO Mindstorms Robot and Java

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  1. LEGO Mindstorms Robot and Java Fall 2004

  2. http://marsrovers.jpl.nasa.gov/mission/spacecraft_surface_rover.htmlhttp://marsrovers.jpl.nasa.gov/mission/spacecraft_surface_rover.html

  3. Java as a Platform • Sun Microsystem has different Java sizes (virtual machines sizes) for devices with different capabilities • Java 2 Enterprise Edition (J2EE) for big machines • Java 2 Standard Edition (J2SE) • Java 2 Micro Edition (J2ME) designed for use with memory-constrained devices • Mobile phones, pagers, PDA’s • JavaCard which is 4KB

  4. LEGO Mindstorms Robot • Robot Kit includes: • RCX (Robotics Command Explorer) • 2 Motors • 2 touch sensors • 1 light sensor • USB infrared transmitter tower • A “gazillion” lego parts to build a robot

  5. LEGO Mindstorms Robot • Robotics Command Explorer (RCX) • Small computer based on the Hitachi H8 microprocessor • Equipped with: • 16 Kb ROM • 32 Kb RAM • 3 motor ports for output • 3 sensor ports for input • 1 LCD display • 1 sound unit • 4 system timers • 6 1.5V batteries • IR port transmitter and receiver

  6. LEGO Mindstorms Robot • RCX runs on 6 AA batteries • When batteries are low, battery icon with an “X” across it will appear in the display • 3 gray ports labeled 1, 2, 3 • Sensor ports • 3 black ports labeled A, B, C • Motor ports

  7. LEGO Mindstorms Robot • 4 buttons • On-Off • Run to executed and stop a loaded program • Prgm to scroll through the loaded programs • May load up to 5 programs at one time • View allows you to view information on a sensor or motor

  8. LEGO Mindstorms Robot • Display Window • A little person standing or running • Indicates that a program is loaded or running respectively • To the right of the little person, a number indicating which of 5 programs will be active when the Run program is pressed • To the left of the little person, the Software Watch • Shows program being downloaded. It counts units of 100 bytes, so a 3 Kb program counts up to ~ 30 • Shows the voltage level of the battery

  9. Programming the RCX • Write a Java program in Eclipse using a LeJOS (LEGO Java Operating System) plug-in • Compile the program transforming it into bytecode • Download the program (bytecode) to the RCX using the IR tower • Firmware interprets the bytecode converting it into machine code • Processor executes the machine code

  10. LEGO Java Operating System • LeJOS is an open source project for UNIX-like and Win 32 systems • Fully functional implementation of Java language • Similar to Java 2 Micro Edition (J2ME) • Originally developed by Jose Solorzano, but is now maintained by Paul Andrews and Jurgen Stuber

  11. LEGO Java Operating System • Limitations of LeJOS: • No garbage collection – garbage collection reclaims memory taken up by objects that are not used in your program • No switch statements; must use nested if….else • No arithmetic on long data type • Maximum array length is 511

  12. LEGO Java Operating System • Provides a Java package to control the RCX: josx.platform.rcx.* • Provides Java classes for working with the RCX features: • Motors • Sensors • Display • Sound • Buttons • IR tower

  13. LEGO Java Operating System TextLCD class: • Uses the display to show text messages. This class uses a great deal of memory. The letters are approximations since the display was originally intended for numbers. public static final void print (String text) - prints the string text on the LCD. Only the first five letters are displayed. public static final void print (char [ ] text) - prints the first five characters of the text array on the display.

  14. LEGO Java Operating System Motorclass: • Used to control the RCX output ports which control the motors. The class contains 3 static Motor instances, A, B, and C, which correspond to the 3 output ports. public final void setPower(int power) - sets the current power level of the motor from 0 to 7. public final void backward( ) - moves the motor backwards. public final void forward( ) - moves the motor forwards. public final void stop( ) - stops the motor. public final void reverseDirection( ) - no matter which way the motor is turning, it makes it turn the other way.

  15. LEGO Java Operating System Buttonclass: • Encapsules 3 RCX buttons View, Prgm, Run. You may call a static instance of each button using VIEW, PRGM, and RUN. public void addButtonListener( ButtoneListener listener) - add a ButtonListener to this Button public final boolean isPressed( ) - returns true is the button is pressed, false otherwise public final void waitForPressAndRelease( ) throws InterrupedException - wait until the button is released

  16. Let’s Try • Create a simple program together that: • Displays a word to the LCD • Start one motor • Run until the RUN button is pressed

  17. You Try • Add to the existing program: • Start the other motor • Play a descending arpeggio before the motors start

  18. Robot Races • Each team must program their robot to complete the race course. Your robot may not go outside the borders of the race course: • Go forward • Stop • Turn 360 degrees to the right and display the message “RIGHT” • Go forward • Turn 360 degree to the left and display the message “LEFT” • Go forward • Play a sound for at least 10 seconds • Go backward • Go forward across the finish line

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