Any help appreciated

[jayjay]

I have written a simple java program to test our 2016 bot. I have update the firmware, image and jre on our 2015 roborio, and updated to the latest version of Eclipse. Our drive consists of four motors – one Talon controller with a y-splitter controls the two left motors, and another Talon with a y-splitter controls the two right motors.

The bot works with a simple arcade drive coded in the teleop method. When I add the setInvertedMotors code (which worked last year), I get “no code” on the bot, a red comm light on the roborio, and the following error:

ERROR Unhandled exception: java.lang.NullPointerException at [edu.wpi.first.wpilibj.RobotDrive.setInvertedMotor( RobotDrive.java:703), org.usfirst.frc.team4951.robot.Robot.robotInit(Rob ot.java:38), edu.wpi.first.wpilibj.IterativeRobot.startCompetit ion(IterativeRobot.java:72), edu.wpi.first.wpilibj.RobotBase.main(RobotBase.jav a:241)]

Here is my code:

import edu.wpi.first.wpilibj.IterativeRobot;
import edu.wpi.first.wpilibj.smartdashboard.SendableChoos er;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboar d;
import edu.wpi.first.wpilibj.Joystick;
import edu.wpi.first.wpilibj.RobotDrive;
import edu.wpi.first.wpilibj.RobotDrive.MotorType;

public class Robot extends IterativeRobot {
final String defaultAuto = "Default";
final String customAuto = "My Auto";
String autoSelected;
SendableChooser chooser;

RobotDrive myDrive;
Joystick stick0, stick1;

public void robotInit() {
chooser = new SendableChooser();
chooser.addDefault("Default Auto", defaultAuto);
chooser.addObject("My Auto", customAuto);
SmartDashboard.putData("Auto choices", chooser);

myDrive = new RobotDrive(0,1); // 0 = left, 1 = right

stick0 = new Joystick(0);
stick1 = new Joystick(1);

myDrive.setInvertedMotor(MotorType.kFrontLeft, true);
myDrive.setInvertedMotor(MotorType.kRearLeft, true);

}

public void autonomousInit() {
//autoSelected = (String) chooser.getSelected();
// autoSelected = Smart;Dashboard.getString("Auto Selector", defaultAuto);
//System.out.println("Auto selected: " + autoSelected);
}

public void autonomousPeriodic() {
switch(autoSelected) {
case customAuto:
//Put custom auto code here
break;
case defaultAuto:
default:
//Put default auto code here
break;
}
}

public void teleopPeriodic() {
myDrive.arcadeDrive(stick0);
}

public void testPeriodic() {

}
}


Any help with the error would be appreciated. Thanks.

[rich2202]

I don't know Java, but my guess is skip using robotdrive.motortype. That class presumes 4 control signals, whereas you only have 2.

Use robotdrive(left channel, right channel) to set your motor channels.

Also, I presume you are using one motor controller per motor, and splitting the Pwm signal. You can't drive 2 cim motors with one controller.

[Joe Ross]

I don't know Java, but my guess is skip using robotdrive.motortype. That class presumes 4 control signals, whereas you only have 2.

Close. It should work with 2, but you have to use the correct 2. It should be kRearLeft and kRearRight.

[jayjay]

Rich/Joe, thanks for the helpful advice.

I will do what Joe has suggested. Thanks again.