Programming

Introduction

• Programming in FRC for 3 years
• Creator of ATALibJ, Gordian, Scouting13, etc.
• Java, python, node

Language

• Java
• Labview
• C++
• Python

Java

• GC

• No Pointers

• Easy extension

• Performance?

Labview

• Not well supported here
• Slow
• Bad!

C++

• Restricted to windriver, mostly
• Performance?!
• Pointers, mem management, ugly (API not designed for nice C code)

The formula

Deployment

• Write code
• Build and/or compile code
• Package the code together
• Throw it on the RIO and reboot

To you, magic.

How code works

Code runs on the RIO

Network connection talks to Driverstation software

User input is translated by drivers on Driverstation, pushed as basic input through network

Output is absolutely stopped by internal libraries when disabled

Robot could run without you - just needs a gamemode signal

Inside the code

There will always be a loop; an instruction will run over-and-over

while ( isTeleoperatedMode() ) {
    drivebase.drive( joystick.getLeftStickValue(), joystick.getRightStickValue() )
}

Read as english...

While it is teleoperated mode, drive the left motors at the same speed as given by left stick value, and right motors at the same speed given by right stick value.

Input to Output

Essentially, find the appropriate way to change output according to input

You need to check the input each time!

eg. 

• Button is on or off - turns motor on 100% or 0%
• Axis should drive at 50% speed - multiply input by 0.5

Fundamentals

ATALibJ

ATALibJ

You don't want to be writing the exact same kind of code for every action and behaviour

You want your code to be readable

You want control over structure and behaviour

You want something open source and consistently maintained

You are cool

ATALibJ

CommandBase

if (CONTROL_STYLE.equals("arcade")) {
    joystick1.addAxisBind(
        drivetrain.getArcade(joystick1.getLeftDistanceFromMiddle(),
                             joystick1.getRightX())
    );
} else if (CONTROL_STYLE.equals("tank")) {
    joystick1.addAxisBind(
        drivetrain.getTank(joystick1.getLeftDistanceFromMiddle(),
                           joystick1.getRightDistanceFromMiddle())
    );
}

• Too long for one slide...

1. Make a driving command, joystick subsystem 
2. Add to OI
3. Docs literally do not tell you!

How readable does this look?

joystick1.addWhenPressed(XboxController.START, 
        new SetSpikeRelay(photonCannon, SpikeRelay.Direction.FORWARDS));
joystick1.addWhenPressed(XboxController.BACK, 
        new SetSpikeRelay(photonCannon, SpikeRelay.Direction.OFF));
joystick2.addWhenPressed(XboxController.A, 
        new EnableModule(winchBack));
joystick2.addWhenPressed(XboxController.A, 
        new SetDualActionSolenoid(winchRelease, DualActionSolenoid.Direction.RIGHT));
joystick2.addWhenPressed(XboxController.B, 
        new DisableModule(winchBack));
joystick2.addWhenPressed(XboxController.B, 
        new SetOutput(winchMotor, 0));
joystick2.addWhenPressed(XboxController.X, 
        new ReverseDualActionSolenoid(loaderPiston));
joystick2.addWhenPressed(XboxController.BACK, 
        new EnableModule(loaderController));
joystick2.addWhenPressed(XboxController.BACK, 
        new SetOutput(loaderController, customSetpoint));
joystick2.addWhenPressed(XboxController.START, 
        new SetOutput(customSetpoint, loaderPosition));
joystick2.addWhenPressed(XboxController.START, 
        new SetOutput(loaderController, loaderPosition));
joystick2.addWhenPressed(XboxController.START, 
        new EnableModule(loaderController));

Taken straight from 2014 competition code

Commands

Command groups are a Command that encompasses multiple commands strung together. It runs commands sequentially or concurrently in groups, in the order of how they are added. 

public final class ShootAndRun extends CommandGroup {
    public ShootAndRun() {
        addSequential(new ChangeRPM(3750));
        addSequential(new Shoot());
        addSequential(new Shoot());
        addSequential(new Shoot());
        addConcurrent(new DriveForwards(1520));
        addConcurrent(new ChangeRPM(3200));
        addConcurrent(new RunGroundPickup());
        addSequential(new Shoot());
        addSequential(new Shoot());
        addSequential(new Shoot());
        addSequential(new Shoot());
    }
}

Commands as an extension of function

Commands used in autonomous and teleoperated

Default commands included

Interacts well with system (internal and external)

Virtually no overhead

Gordian

Gordian and equivalent tools

Imagine autonomous like this

Text file with script held on RIO

Edit on-the-fly, push changes by FTP

Custom variables, actions, commands, extensions

Interact at a low level with the code

Gordian

def concat(x, i)

    def _concat(j, w, e)
        if(e > 0)
            return _concat(j + w, w, e - 1)
        else
            return j
        end
    end
    
    return _concat("",x,i)
end
 
 
print(concat("Hello World", 3))

Recursion, classes, methods, math, variables, and more

Greyhound Lua

Developed by 973 for 2011 (they won worlds that year)

Not actively maintained

Lua syntax and feature set

while num < 50 do
  num = num + 1
end

if num > 40 then
  print('over 40')
elseif s ~= 'walternate' then
  io.write('not over 40\n')

Technical Challenges

Main things you'll encounter

• Largely input and output
• Control loops
• Class structure and code organization
• Revision and version management
• Moving featureset - be ready to code at all times!

Honest experience

From someone who spent hours doing this...

• Lots of deployment problems out of your control
  • Talk to electronics
• Lots of opposite behaviour
• Lots of wrong port numbers
• Lots of unnecessary features

Support Network

Your support network

1. Other student
2. Mentor
3. Chief Delphi
4. Stack Overflow
5. Me!

Planning ahead of time

You should start in week 1-2

All features should be functional by week 4

Learn the basics ahead of time - get familiar with the workflow

Install things before; that is a stupid thing to stall you

Programming team

• Should never be over 5 people

• Better to have 100% dedicated members

• Leadership roles

  • Programming team leader

  • Programming mentor

• Member roles

  • Organization (version control, etc.)

  • Documentation

  • Code Review (bug fixes, etc.)

• Depends on your time commitment

• Depends on your experience

  • Version control?

  • Formal or casual process?

• Can be adjusted according to needs

  • Team took on a really ambitious programming goal?