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INTRODUCTION TO JAVA PROGRAMMING
FOR THE FIRST ROBOTICS COMPETITION
JONATHAN DANIEL
HEAD PROGRAMMER
FERNBANK LINKS
DISCLAIMERS
• This session WILL NOT teach you all of Java.
• This session WILL teach you how to use your knowledge of Java with the FRC Java Libraries.
WHAT IS PROGRAMMING?
PROGRAMMING IS…
• Computer programming is the craft of writing useful, maintainable, and extensible source code which can
be interpreted or compiled by a computing system to perform a meaningful task.
• FRC Programming Languages
•
•
•
•
C++
Java
Python
LabVIEW
REVIEW OF JAVA
• Java is an object-oriented programming
language.
• Object-oriented programming (OOP) is a
programming language model organized around
objects rather than "actions" and data rather than
logic.
• A Java program can be separated into different
classes, which are templates for creating objects
with different behaviors.
WHAT’S IN A CLASS?
• Java classes contain methods and variables.
• All Java class files end with the extension .java .
• A method is a function that can be executed by a
• In order for a class to read another class, you
class. Sometimes, you will have a method that
returns some form of data to the robot.
• One method could be to ask the robot how much
battery power it has.
• A variable is a container for data.
• Variable X = 9
• Variable Y = “These three words”
have to use an import statement.
• When you use an import statement, all of the
public methods in that class will be absorbed into
your new class.
• For example, you might import class1 into class2,
so you can use class1’s methods!
IMPORTANT JAVA KEYWORDS
• A keyword is a special word/phrase that is
used to define some aspect of a class, method
or variable.
• Public
• All other classes can see this method/variable.
• Private
• This method/variable will only be seen in its
current class.
• Protected
• This method/variable can only be seen by
subclasses of the current class.
• Extends
•
This is when the class becomes a subclass of
another class.
• Public class Dog extends Animal
• Import
•
When you load all of another class’s public
methods/variables into your own class.
• New
•
Creates a new object of a certain class.
TYPES OF OBJECTS
• Objects are digital items that can be referenced by
computers.
• There are many types of objects, but these are the
most common ones.
• Integer
• Any number that doesn’t contain a decimal point.
• Double
• Any number that does contain a decimal point.
• Boolean
• A binary variable that can be interpreted as true or false.
• String
• Any text that is surrounded by double quotation marks.
• Void
• This will only be used with methods, and it means that the
method returns nothing.
• Static
• No matter how many objects of this type are created,
there will only be one of this method OR variable.
LET’S DO A QUICK QUIZ!
WHAT TYPE OF OBJECT IS 9.0 ?
A. Integer
B. String
C. Double
D. Boolean
WHAT TYPE OF OBJECT IS “TRUE”?
A.
Double
B.
C.
String
D.
Integer
Boolean
THE MOST IMPORTANT ASPECT OF JAVA!
• Semicolons are one of the most important
symbols in Java!
• Unless you are creating a method or loop, you
have to use a semicolon to end the a line of code.
• This lets the program know that it has reached the
end of a line and it needs to move to the next
one.
WHAT DO I USE TO PROGRAM MY ROBOT?
INTRODUCE THE ECLIPSE IDE
PACKAGE EXPLORER
• The package explorer is a file explorer for all of
your Eclipse Projects.
• Eclipse Project = Java Program
• Packages are folders that can be used to contain
java classes
• When you create a robot project using the iterative
template, Eclipse will create a default package and
a default class.
• Org.usfirst.frc.team0000.robot
• Robot.java.
• Depending on your robot’s functions, you may want
to create different packages for each function.
CONSOLE
• Will document the deployment of your code to
the robot, so you will know if it was successful.
THE PROGRAMMABLE ELECTRONICS
ROBORIO
• Main Robot Controller
• RIO to PC Communication
• Ethernet
• USB Cable
• Wireless (if Radio is configured)
• 10 Pulse Width Modulation Ports (0-9)
• Controls the Motors
• 10 Digital Ports (0-9)
Digital
PWM
• Communicates with digital sensors
• 4 Analog Ports (0-3)
• Communicates with analog sensors
Analog
JOYSTICKS
MOTOR CONTROLLER
• PWM - Pulse Width Modulation
• To control the speed of the motor, the speed controller
switches the full input voltage on and off very quickly.
• There are ten PWM ports on the RoboRIO, and each
port controls one motor.
• Most PWM classes use set(speed) methods to
determine the speed of the motor.
• The parameter is a double value that ranges from -1.0
to +1.0, with 1.0 being full forward and -1.0 being
full reverse.
• Inversion of Motors
• Typically, you will need to set one of your motors to
interpret +1.0 as -1.0 by using setInverted().
• CAN – Controller Area Network
• More advanced form of control that allows for
feedback.
LET’S PROGRAM A ROBOT TO DRIVE AROUND!
CONTROLLING PNEUMATICS
THE MAIN ELECTRONICS
OVERVIEW OF PNEUMATICS
Outside
Environment
Compressor
Air Tanks
Solenoids
Actuators
PNEUMATICS OVERVIEW – PNEUMATICS CONTROL MODULE
• The Pneumatics Control Module is the mechanism
that is responsible for the management of the
compressors and solenoids on the robot.
• 8 Solenoid Ports
• 8 Single Solenoids
• 4 Double Solenoids
• 1 Compressor Port
• Pressure Relief Valve Port
WHY USE PNEUMATICS?
LET’S PROGRAM A SHIFTING DRIVETRAIN!
SENSORS
WHY USE A SENSOR?
SYSTEM.OUT.PRINTLN(‘MESSAGE’)
SYSTEM.OUT.PRINT(‘MESSAGE’)
THE SENSOR FAMILY TREE
Sensors
Analog
Gyro
Encoder
Accelerometer
Digital
Encoder
Limit Switch
ANALOG VS. DIGITAL
Analog Sensors
• These sensors can return any value based on whatever they are
measuring.
• Encoders act like Analog Sensors, but are technically digital
sensors.
Digital Sensors
• Digital Sensors return one of two values, either a 1 or a 0.
• Encoders are the odd member of the family.
LET’S HAVE OUR ROBOT TELL US ABOUT OUR GYRO!
CAMERAS IN FRC!
CAMERAS
LET’S PROGRAM OUR ROBOT TO STREAM VIDEO!
NETWORKING
• If you are using an IP Camera, you will have to
assign it an IP Address.
• 10.TE.AM.11
• A good static address should be safe from other
internet devices.
• 10.08.00 for Team 800
• Subnet 255.255.255.0
• 10.44.68.11
• The FMS allows each team to use a bandwidth of
7 megabits/second.
• 6 Mbps after driver station packets.
• If you plan on streaming your camera to the
driver station, you will probably need to use
compression.
RESOURCES – FRC STACK
• WPILib ScreenSteps Tutorials
• https://wpilib.screenstepslive.com/s/4485
• API Documentation
• http://first.wpi.edu/FRC/roborio/release/docs/java/
• Chief Delphi
• https://www.chiefdelphi.com/
• GitHub
• GitHub Student Developer Pack: https://education.github.com/pack
• Fernbank LINKS GitHub: https://www.github.com/fernbanklinksrobotics
• Team GitHub List
• http://bit.ly/TeamGithubs
RESOURCES – LEARNING JAVA
• Codecademy
• www.codecademy.com
• Start:Code
• Classes in the Decatur Area
• www.startcode.net
• AP Computer Science
• Teaches CS with Java
QUESTIONS?
EMAIL: [email protected]