Retrieving data

Unlike SmartDashboard.getNumber and friends, retrieving data from Shuffleboard is also done through the NetworkTableEntries, which we covered in the previous article.

JAVA

class DriveBase extends Subsystem {
   private ShuffleboardTab tab = Shuffleboard.getTab("Drive");
   private GenericEntry maxSpeed =
      tab.add("Max Speed", 1)
         .getEntry();
   private DifferentialDrive robotDrive = ...;
   public void drive(double left, double right) {
      // Retrieve the maximum speed from the dashboard
      double max = maxSpeed.getDouble(1.0);
      robotDrive.tankDrive(left * max, right * max);
   }
}

PYTHON

import commands2
import wpilib.drive
from wpilib.shuffleboard import Shuffleboard
class DriveSubsystem(commands2.SubsystemBase):
   def __init__(self) -> None:
      super().__init__()
      tab = Shuffleboard.getTab("Drive")
      self.maxSpeed = tab.add("Max Speed", 1).getEntry()
      this.robotDrive = ...
   def drive(self, left: float, right: float):
      # Retrieve the maximum speed from the dashboard
      max = self.maxSpeed.getDouble(1.0)
      self.robotDrive.tankDrive(left * max, right * max)

This basic example has a glaring flaw: the maximum speed can be set on the dashboard to a value outside [0, 1] - which could cause the inputs to be saturated (always at maximum speed), or even reversed! Fortunately, there is a way to avoid this problem - covered in the next article.