1. Fe Maidens Programming 2017-2018
Mechanism Coding
Fe Maidens Programming

2. Agenda Lift Review Shooters and Hitters Grippers
Writing Code for a spring-style hitter
Grippers
Writing code for a roller arm

3. Lift Review
Last time, you wrote code for lifts. There are 3 major types- do you know what they are?

4. Lift Review
Last time, you wrote code for lifts. There are 3 major types- do you know what they are?
Power Up/Down: Single stage lifts - simple but big.
Cascade: Multi stage lift, all stages move at once. Smaller, but often only has an up and a down.
Continuous: Multi stage lift, stages move consecutively. Sort of a cross between power and cascade, but slower than either.
Telescopic and scissor lifts are also sometimes used, but rarely due to their complexity and relative structural weakness.

5. Lift Review
Look over your code from last Monday on lifts- any lingering questions? This is an example of a power up/down lift.

6. package org.usfirst.frc.team2265.robot.subsystems;
import edu.wpi.first.wpilibj.command.Subsystem;
import edu.wpi.first.wpilibj.CANTalon;
import edu.wpi.first.wpilibj.Joystick;
public class Forklift extends Subsystem {
//creates CANTalons for the lift
CANTalon topMotor = new CANTalon(1);
CANTalon bottomMotor = new CANTalon(2);
//defines the speeds that the motors turn at as variables
private final static double UP = 0.5;
private final static double DOWN = -0.5;
private final static double STOP = 0.0;
private final int axis = 1;
//creates the Joystick that controls the lift’s movement
public atkJoy = new Joystick(1);
/*the methods that move the lift up or down
This method moves the lift up at a constant speed*/
public static void up() {
topMotor.set(UP);
bottomMotor.set(UP); }
//makes the lift go down at a constant speed
public static void down() {
topMotor.set(DOWN);
bottomMotor.set(DOWN);
//stops the lift from moving
public static void stop() {
topMotor.set(STOP);
bottomMotor.set(STOP);
// tell forklift to move up, down or stop moving based on joystick position
//if joystick is in the up position, move lift up
//if joystick is in its default position, stop
// if joystick is in the down position, move down
public void helper() {
private double Val = atkJoy.getRawAxis(axis)
if (Val > 0) {
up();
else if (Val < 0){
down();
else {
stop();
public void initDefaultCommand(){
setDefaultCommand(new MoveForkLift());

7. package org.usfirst.frc.team2265.robot.commands;
import edu.wpi.first.wpilibj.command.Command;
import org.usfirst.frc.team2265.robot.Robot;
Import org.usfirst.frc.team2265.robot.subsystems.ForkLift;
public class MoveForkLift extends Command {
public MoveForkLift(Robot.ForkLift) {
// Use requires() here to declare subsystem dependencies
requires(Robot.ForkLift); }
// Called just before this Command runs the first time
protected void initialize() {
// Called repeatedly when this Command is scheduled to run
protected void execute(){
Robot.ForkLift.helper();
// Make this return true when this Command no longer needs to run execute()
protected boolean isFinished() {
return false;
// Called once after isFinished returns true
protected void end() {
// Called when another command which requires one or more of the same
// subsystems is scheduled to run
protected void interrupted() {

8. Shooters/Hitters
These mechanisms are used to eject game pieces from the robot.
Types of Shooters:
Turret: Wheel(s), and often an aiming chute
Roller: Sets of parallel powered rollers
Types of Hitter:
Catapult: Uses a turning motion like a throw to launch the piece
Piston: “punches” the game piece (best for light objects)
Spring: Uses spring force pulled back and released via a (can also use surgical tubing)

9. Code the Piston Hitter
A piston releases, and then after a moment the gate- latch piston also releases. Write a subsystem to control both, and a command that will allow for us to test for the optimal time delay later on.
What are the advantages and disadvantages of using this method?

10. package org.usfirst.frc.team2265.robot.subsystems;
import edu.wpi.first.wpilibj.command.Subsystem;
import edu.wpi.first.wpilibj.DoubleSolenoid;
import edu.wpi.first.wpilibj.DoubleSolenoid.Value;
import edu.wpi.first.wpilibj.Timer;
public class PistonHitter extends Subsystem {
// Put methods for controlling this subs ystem
// here. Call these from Commands.
// Instances of the double solenoids and the timer
DoubleSolenoid bigPiston;
DoubleSolenoid gatelatchPiston;
static Timer t = new Timer();
Public pistonHitter(int BigOutport, int BigInport, int SmallOutport, int SmallInport) {
bigPiston = new DoubleSolenoid(BigOutport,BigInport);
gatelatchPiston = new DoubleSolenoid(SmallOutport,SmallInport); }
public void firePiston {
bigPiston.set(DoubleSolenoid.Value.kForward);
t.delay(3.0);
gatelatchPiston.set (DoubleSolenoid.Value.kReverse);

11. package org.usfirst.frc.team2265.robot.commands;
import edu.wpi.first.wpilibj.command.Command;
import org.usfirst.frc.team2265.robot.Robot;
Import org.usfirst.frc.team2265.robot.subsystems.PistonHitter;
public class shootPiston extends Command {
public shootPiston(Robot.PistonHitter) {
// Use requires() here to declare subsystem dependencies
requires(Robot.PistonHitter); }
// Called just before this Command runs the first time
protected void initialize() {
// Called repeatedly when this Command is scheduled to run
protected void execute() {
Robot.ph.firePiston();
// Make this return true when this Command no longer needs to run execute()
protected boolean isFinished() {
return false;
// Called once after isFinished returns true
protected void end() {
// Called when another command which requires one or more of the same
// subsystems is scheduled to run
protected void interrupted() {

12. Grippers
Most grippers are rollers. Some move on manipulatable arms, to go down over a game piece.

13. Coding a Roller Arm
A motor manipulates the arm, moving it up and down. Then, a second motor spins a roller to bring in the game piece. After, the arm moves back up to complete the movement.
Write a subsystem to control the motors and a command that will retrieve a game piece from the field.

14. package org.usfirst.frc.team2265.robot.subsystems;
import edu.wpi.first.wpilibj.command.Subsystem;
import edu.wpi.first.wpilibj.CANTalon;
import edu.wpi.first.wpilibj.Timer;
public class RollerArm extends Subsystem {
public CANTalon armMover;
public CANTalon spinMotor;
public static Timer t = new Timer();
public RollerArm (int armMoverPort, int spinMotorPort) {
armMover = new CANTalon(1);
spinMotor = new CANTalon(2); }
/*Put methods for controlling this subsystem
here. Call these from Commands. */
public void initDefaultCommand() {
// Set the default command for a subsystem here.
//setDefaultCommand(new MySpecialCommand());
public void up(){
armMover.set(-1.0);
t.delay(0.1);
armMover.set(0);
public void down(){
armMover.set(1.0);
// speed has a sign
public void spin(double speed){ //think: what do you need to make this spin different speeds?
spinMotor.set(speed);

15. Gear Chute:

16. package org. usfirst. frc. team2265. robot
package org.usfirst.frc.team2265.robot.subsystems; //creates imports import org.usfirst.frc.team2265.robot.RobotMap; import edu.wpi.first.wpilibj.command.Subsystem; import edu.wpi.first.wpilibj.DoubleSolenoid.Value; import edu.wpi.first.wpilibj.DoubleSolenoid; /** * */ // makes gear chute subsystem// public class GearChute extends Subsystem { // intializes doubleSolenoid for the gearChute public static DoubleSolenoid gearPistons = new DoubleSolenoid(RobotMap.gearPort1, RobotMap.gearPort2); public static DoubleSolenoid basePistons = new DoubleSolenoid(RobotMap.basePort1, RobotMap.basePort2); // Extends the piston public static void extend() { gearPistons.set(DoubleSolenoid.Value.kForward); basePistons.set(DoubleSolenoid.Value.kForward); } // Retracts the piston public static void retract() { gearPistons.set(DoubleSolenoid.Value.kReverse); basePistons.set(DoubleSolenoid.Value.kReverse); } // Put methods for controlling this subsystem // here. Call these from Commands. public void initDefaultCommand() { // Set the default command for a subsystem here. // setDefaultCommand(new MySpecialCommand()); } }

17. package org. usfirst. frc. team2265. robot. commands; import org
package org.usfirst.frc.team2265.robot.commands; import org.usfirst.frc.team2265.robot.subsystems.GearChute; import edu.wpi.first.wpilibj.command.Command; /** * */ public class ShiftChute extends Command { boolean down; public ShiftChute(boolean u) { // Use requires() here to declare subsystem dependencies // eg. requires(chassis); down = u; } // Called just before this Command runs the first time protected void initialize() { } // Called repeatedly when this Command is scheduled to run protected void execute() { // retract if piston off/extended // if (GearChute.gearPiston.get().equals(Value.kForward) || // GearChute.gearPiston.get().equals(Value.kOff)) { if (down) { GearChute.extend(); return; } // extend if piston is retracted // if (GearChute.gearPiston.get().equals(Value.kReverse)) { if (!down) { GearChute.retract(); return; } } // Make this return true when this Command no longer needs to run execute() protected boolean isFinished() { // return true means the clause is now true, so the command will stop // executing return true; } // Called once after isFinished returns true protected void end() { } // Called when another command which requires one or more of the same // subsystems is scheduled to run protected void interrupted() { } }