Part 0 Installing LeJos

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Getting Ready to go with LeJos and an IDE
NSF Workshop November 19-21, 2004 The University
of Mississippi Pam Lawhead
2
Part 0 Installing LeJos

• Taken from
• http//lejos.sourceforge.net/tutorial/getstarted/f
  irstbrick/win32.html

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Step 1
You will need LEGO MINDSTORMS RCX, IR Tower
and the leJOS environment and The JavaTM 2
Platform, Standard Edition download it from
http//java.sun.com/j2se/1.4/download.html and
to consult the associated installation
instructions (make sure to download the SDK, not
the JRE!).
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• The leJOS environment may be downloaded from
• Download section of http//www.lejos.org.
• Installation of the leJOS environment
• After you have downloaded the leJOS environment
  zip file, unzip it directly to your C directory.
• Add the SDK's bin directory to your PATH
  environment variable. (Using Start/Control
  Panel/System/ advanced/environment variables
• In XP Start/Control Panel/Performance and
  Maintenance/System/advanced/
• environment variables
• 4. Set the LEJOS_HOME environment variable to
  the directory you installed lejos into set
  LEJOS_HOMElt your lejos directory gt
• 5. Add leJOS's bin directory to your PATH
  environment variable set PATHPATHLEJOS_HOME
  \bin
• 6. Add the leJOS classes to your CLASSPATH
  environment variableset CLASSPATHCLASSPATH.
  LEJOS_HOME/lib/classes.jarLEJOS_HOME/lib/pcrc
  xcomm.jar
• 7. Set the RCXTTY environment variable to your
  'tower' deviceset RCXTTYCOM1 or set RCXTTYUSB

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RCX Firmware

• leJOS-enable your RCX
• To enable your RCX for the execution of leJOS
  programs,
• you will have to replace the original LEGO with
  the leJOS operating system.
• Place the IR sensor of the RCX in front of the IR
  Tower
• Turn on the RCX
• Open a command shell and change to the bin
  directory of your
• leJOS installation
• call firmdl.bat
• The progress of the download is displayed in the
  command shell
• and on the display of the RCX
• the RCX will double beep when the download is
  complete
• and display the battery voltage
• OR

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Use the RXC Direct Interface Available from
http//lejos.sourceforge.net/utilities.html

• Download the file RCXTools1.5.zip
• Unpack "RCXTools_1_5.zip
• doubleclick"RCXDownload.bat"
• Set up preferences as in Get Started slide
• Download firmware using button
• GETTING STARTED

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Setting up the IDE

• NSF Workshop November 19-21, 2004
• The University of Mississippi Pam Lawhead

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Setting up the IDE

• http//rcxtools.sourceforge.net/e_download.html
• Download RCXTools_1.5.zip
• Double Click "RCXDownload.bat"
• You will now participate in the dialog that
  follows

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Here put the path to your lejos bin directory
Here put the path to your JDK
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Set Up Continues
Used courtesy of RCX Tools Install page
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Let us test it

• Create Program Hello World
• Save it as HelloWorld.java
• Run RCXDownload.bat
• Use the Open button to find the file
• Load the file
• Use the Compile button to compile

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helloWorld.java
import josx.platform.rcx. public class
HelloWorld public static void main
(String aArg) throws Exception
LCD.clear()
TextLCD.print ("hello")
Thread.sleep(2000) TextLCD.print
("world") Thread.sleep(2000)

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(No Transcript)
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Download program to RCX

• Place robot in front of IR Tower
• Be careful to cover it if you are not alone
• Turn Robot on
• Click IDE Download Button
• Watch numbers on LCD if they are not increasing
  try again

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Run the Program

• When the robot beeps twice
• Hit the RUN button
• You will see
• HELLO
• WORLD

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LeJos, Mindstorm Links
http//lejos.sourceforge.net/tutorial/index.html h
ttp//lejos.sourceforge.net/ http//dudley.wellesl
ey.edu/anderson/robots/lejosdocs/ The Lejos
API http//www.informatik.fh_muenchen.de/schieder
/usinglejos http//dudley.wellesley.edu/anderson/
robots/lejos/ http//lvi.sourceforge.net/
Another way to interface with LeJos http//rcxtool
s.sourceforge.net/ My Favorite
IDE http//graphics.stanford.edu/kekoa/rcx/ How
the internals of the RCX work http//www.informati
k.fh_muenchen.de/schieder/usinglejos/
Instant Lejos For a quick uncomplicated
approach http//mindstorms.lego.com/eng/default.as
p The Official Lego Mindstorm site http//www.dev
daily.com/java/lejos/GettingStartedWithLejos/
Another Introductory Site
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Using LeJos

• NSF Workshop November 19-21, 2004
• The University of Mississippi Pam Lawhead

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Button and LeJos

• All buttons my be re-programmed except RUN
• Controlled by a button class
• Polling or Using a Listener (Discuss)
• listener or directly using waitForPressAndRelea
  se()

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Button Example(Polling)
import josx.platform.rcx. public class
RunButton public static void main(String
args) throws InterruptedException // Move
forward Motor.A.forward()
Motor.B.forward() // just run until RUN button
is pressed again Button.RUN.waitForPressAndRe
lease()
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Button Example(listener) -from Tutorial
public class MyButtonListener implements
ButtonListener public void
buttonPressed(Button b) // maybe do
something here // buttonPressed()
public void buttonReleased(Button b) //
maybe do something here //
buttonReleased() // class MyButtonListener
//used it looks like this Button.RUN.addButtonList
ener(myButtonListener)
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Motors

• Three Motors A, B, C
• Controlled using
• public static void forward()
• public static void backward()
• public static void reverseDirection()
• public static void flt()
• public static void stop()

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Motor Examples

• Motor.A.forward()
• Motor.B.forward()
• Motor.B.flt() //like an idle
• Motor.A.reverseDirection()
• Motor.A.setPower(3) //possible values 1-7
• (deceptive does not cause the motor to go slow
  it just causes to use less energy which, perhaps,
  might slow it down)

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Sensors

• There are three possible Sensor.S1, Sensor.S2,
  Sensor.S3
• You must set type and mode to know the type of
  the sensor
• setTypeAndMode(int aType, int aMode)
• Parameters include
• aType _ 0 RAW, 1 TOUCH, 2 TEMP, 3 LIGHT,
  4 ROT
• aMode _ 0x00 RAW, 0x20 BOOL, 0x40 EDGE,
  0x60 PULSE, 0x80 PERCENT, 0xA0 DEGC, 0xC0
  DEGF, 0xE0 ANGLE
• Also, mode can be OR'd with slope (0..31).

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More Sensors

• Sensor.S1.activate() //turns the sensor on
• Sensor.S1.passivate() //turns the sensor off
• Same argument exists
• Do I want listeners or do I poll?
• (see Barnes article for full discussion)

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Sensor Examples

• Sensor.S2.readRawValue()
• (must be used if aType 0)
• Sensor.S2.readBooleanValue()
• (used if aMode BOOL e.g. touch sensor)
• Sensor.S2.readValue()
• (used for light sensor percentage
• aMode 3
• aType 0x80)

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Sensor Code Example
import josx.platform.rcx. class LCDShowLight
public static void main(String args)
Sensor.S1.setTypeAndMode(3,0x80)
Sensor.S1.activate() while(true)
LCD.showNumber(Sensor.S1.readValue())

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Sound

• Uses RCX speaker useful for debugging
• beep //one beep
• beepSequence() // a series of beeps going down
• buzz()
• playTone(int aFrequency, int aDuration)
• aFrequency 31-2100 Hz //human sound range
• aDuration 1 256 Centiseconds

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Sound Example
import josx.platform.rcx. class AudibleSounds
public static void main(String args)
throws InterruptedException for(int f
440 f lt 10000 f 110f/100)
LCD.showNumber(f) Sound.playTone(f,
50) Thread.sleep(500)
for(int f 440 f gt 20 f 90f/100)
LCD.showNumber(f) Sound.playTone(f,
50) Thread.sleep(500)
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Part 4Doing an AssignmentThe Light Sensor

• NSF Workshop November 19-21, 2004
• The University of Mississippi Pam Lawhead

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Assignment

• The Light Sensor

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The Sensors

• Normally, there are three types of sensors used
  programming the RCX, and they are
• Touch Sensor
• Light Sensor
• Rotation Sensor
• This assignment will focus on the Light sensor.

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Overview

• The purpose of this assignment is to give the
  student experience in Java event programming
  involving light sensors. It will give students
  more chances to practice using the RCX-Lejos LCD
  screen control, the If statement, and additional
  loop control skills.

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The Lego Mindstorm with Light and Touch Sensor

• The sensor illuminates whatever is in front of it
  with an LED (light emitting diode) and records
  the amount of light it get back with a
  photo-sensitive device.
• This photo-sensitive device returns a signal that
  is amplified and digitized (transformed into a
  number).
• The range of values for the signal is 0(dark) to
  100(bright).
• The value measured will vary with the surface it
  examines, the distance separating it, and the
  ambient light (environment)

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The Lego Mindstorm with Light Sensor

• The LEGO Mindstorms light sensor has a range of
  about 3 inches.
• In Java, the sensor can measure the percentage of
  light received by the photo sensitive device.
• The RCX, displays a lower percentage of light on
  black colors and a higher percentage on white
  colors.
• The robot can follow a path by reacting to light
  percentages.

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Problem Statement

• Write a small Java program to demonstrate to how
  the light sensor works. There are three
  different colors used on the background surface,
  (black, green, and white). Through the program,
  the LCD should show the percentage of light
  corresponding to different colors on the
  background. When the light sensor is on white,
  there should be a range of numbers, on green
  another, and finally on black another.
• Battery power and ambient light will affect
  how the machine behaves.
• Using data gained from above experiment, write a
  Java program to make an RCX, equipped with one
  light sensor and at least two wheels, navigate on
  flat surfaces and follow the black line.

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Laboratory Preparation

• How does this program get input data or receive
  data in this lab? What is the difference from
  the previous labs?
• How many variables do you plan to use? And what
  data types are the variables?
• Write a small method called LeftAndRight that
  makes the RCX turn left or turn right based on
  some value that it receives?
• Write the program outline for the testing light
  sensor assignment.
• Write the method headers for this assignment.
  Once this is done write the full code. Bring
  this code to the lab.

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Laboratory

• Robot Needed
• RCX brick, 2 motors, 2 or 4 wheels, and 1 light
  sensor.
• Lejos classes and method needed
• Motor setPower (int aPower), forward(),
  backward(), stop()
• Sensor activate(), passvate(), int
  readPercentage() (for light sensor)
• LCD showNumber(int value)
• Other equipment
• Track
• IR Tower

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Solution Strategy

• Fix the light sensor at a 90 degree angle to
  surface. Allow no more than 3 inches from
  sensors to surface.
• The key to functionality is using the method
  readPercentage() of the class Sensor,
• Sensor.S1.readPercentage() returns an integer
  value representing the percentage of light
  received.
• The shape of the trace is ellipsoid. Set one
  Motor to stop and allow the other Motor to move
  forward, causing the RCX to turn left or right.
• When executing, watch direction RCX is moving.
  If the program allows the RCX to turn left, keep
  the left side of the RCX inside of the black
  line. Otherwise, place right side on the inside.

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Testing

• Stand in different places when checking the color
  percentages.
• Start Robot on Green, on White, on Black
• What happens if you reverse directions?
• Could you adjust if you had to change directions?
  How?

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Submissions

• Answers to Pre-Lab questions
• Brief description of expectations before lab
• Discussion of how time was spent in lab
• How long did lab take, including Pre-Lab
  preparation?
• A list of the problems encountered writing code
  for lab.
• A list of the problems had running and using lab.
• Names and roles of any collaborators
• Email program after demonstration

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Assignment Array Sorter

• NSF Workshop November 19-21, 2004
• The University of Mississippi Pam Lawhead

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Overview

• The purpose of this assignment is to give the
  student experience using Java arrays, light
  sensors and arrays to sort the sensor reading
  stored in an array.
• The text used for this class (Lambert and
  Osborne) provides code for sorting a simple on
  dimensional array. This code may be used in
  this assignment. The only sensor required is a
  light sensor.
• You need to read Chapter 7 in your textbook very
  carefully to understand classes. Next, you need
  to answer the following questions BEFORE you come
  to lab.

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Background
The array data structure is provided by the Java
programming language to handle those situations
where many similar items need to be read,
manipulated, stored, written or dealt with by
the computer in some way. . . . The actual
assignment has an extensive background section
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Problem Statement
You have been chosen as the field tester for the
Our Colors Dont Fade in the Sun Paint company.
The sun shines unrelentingly here in summertime
Mississippi and you have decided that it is
entirely too hot for you to go out each day and
take the readings from each color sample to
determine if there has been any change. The goal
is to keep the colors stored in the companys
primary computer from lightest to darkest. To
do this you must write a program that allows a
robot to travel across a field of sample paint
colors, take a reading of each using the light
sensor, and then store that value in an array of
colors. Once the colors have been collected, you
need the robot to return those values to the
main computer where they will be stored and
sorted for future use. Your company is a
start-up company so it is not making many
different colors of paint at this time. In this
case, summer paint sun test there are only 5
colors that are being tested. As profits
increase, the company will add additional colors
to its a pallette but, for now, 5 will do.
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Lab Preparation

• 1. What is the Java syntax for declaring an
  array?
• 2. What new leJos classes will you need to
  complete this assignment?
• 3. What are constructors used for? How are they
  defined?
• 4. What is the simplest way that you can sort a
  list of numbers?
• 5. What are the classes that have you already
  written that can be reused here?
• 6. Will you need two arrays to sort the numbers?
  How will you handle that?

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Laboratory

• Robot needed RCX brick, two motors, 4 (or 2)
  wheels and one light sensor
• LeJos classes and methods needed
• Motor setPower(int aPower), forward(),
  backward(), stop(),flt()
• Sensor activate(), passvate(), int
  readPercentage()(for light sensor )
• LCD showNumber(int value), RCXComm

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Solution Strategy

• (Note You might need to write a little test
  program to determine the light sensor percentage
  for the different colors.)
• You need to be sure that the paint colors are
  distinct enough that the different colors can be
  recognized by the. You might need to put a black
  line between the colors.
• You need to first identify the different parts of
  your program - objects, attributes and methods.
• Decide what variables that you will need. What
  methods will be required to access these
  variables?
• Using the description of a class template found
  in your book on p. 160 define each of the four
  parts of your robot class template.

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Solution Strategy (continued)

• Write each of the methods that you have
  identified in step one.
• How will you get your robot to return values to
  the PC? What class will you use?
• What methods in that class will be required?
  What are the arguments required?
• Hint You might have a problem with the robot
  running too fast to get accurate readings of each
  of the colors, what are some solutions to that
  problem?

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Testing

• 1. What is the first thing that you need to
  test?
• 2. What should the output from this program look
  like?
• 3. What is the input?
• 4. What would be an example of the program not
  working?
• 5. What would you do to fix the problem
  identified in question 4?
• 6. What are the expected inputs and outputs of
  each module?
• 7. What would it mean for a value to be out of
  bounds for each module?
• 8. What are two different ways that an array
  could be out of bounds?