NetworkTablesInput

This is a small utility library that the ESHS P.O.T.A.T.O.E.S. have been using for the past few years to allow robots to be controlled with the keyboard.

It works by capturing keyboard and mouse input in a dedicated JavaFX window and translating these into boolean values in NetworkTables, a sort of distributed hashtable provided by WPILib. Robot code can then read known key strings from the input NetworkTable in order to figure out what the user has pressed.

Credit goes to @amclees for the original idea.

Dependencies

This code has hard dependencies on NetworkTables and JavaFX. Both must be present in the $CLASSPATH in order to build and to run, and JavaFX must also be present in the $MODULEPATH. The Gradle build normally takes care of all this, producing a "fat JAR" with all of the dependencies included within.

How to build

To build this project and download all its dependencies, simply run:

./gradlew build

from the current directory. If all goes well and you have a solid Internet connection, this should result in a build artifact called ./build/distributions/networkworktablesinput.zip.

How to run

This program must be run from the driver station -- usually a Windows laptop.

1. To run NetworkTablesInput from the ZIP file, unzip it to any location, enter that folder, and run bin/networktablesinput (on Unix) or bin/networktablesinput.bat (on Windows) directly.

2. If you happen to have cloned this source tree onto the driver station laptop, you can also enter that directory and execute:

   ./gradlew run

   The NetworkTablesInput program will be executed in-place.

3. Finally, if Gradle isn't working for whatever reason, you can run NetworkTablesInput by hand. It's not easy, though:

   1. Download a Gluon SDK build of OpenJFX from https://gluonhq.com/products/javafx.

   2. Unzip the build into some folder, like %USERPROFILE%\Downloads.

   3. cd into the directory where networktablesinput.jar is located and run the following:

      java -classpath "%USERPROFILE%/Downloads/javafx-sdk-11.0.2/lib/*;networktablesinput.jar" \
           --module-path="%USERPROFILE%/Downloads/javafx-sdk-11.0.2/lib" \
           --add-modules=javafx.controls,javafx.fxml \
           main.NetworkTablesInput

      changing the version number for the JavaFX SDK as appropriate.

      You're really better off sticking with Gradle.

Troubleshooting

• When I try to run, I get a java.lang.UnsatisifedLinkError in ntcorejni.dll that says "Can't find dependent libraries."

  This is a common problem, and it indicates that you need to install the latest Visual C++ redistributable. This seems to only be a problem for people who use the offline WPILib installer.

How to use

• As NetworkTablesInput runs, keypresses and mouse clicks are captured in a blank JavaFX window and passed into the edu.wpi.first.networktables.NetworkTable table called inputTable as long as the window has the focus. Every entry placed into the table is a boolean value indicating whether the key is pressed. The keys themselves are just members of the javafx.scene.input.KeyCode enumeration, converted to strings. Examples include:

  Keyboard key	NetworkTables key string
  Alphabetical	Uppercase of the key (i.e. A, B, C, ...)
  Numbers	DIGIT1, DIGIT2, ...
  Mouse buttons	Left Mouse, Right Mouse
  Function keys	F1, F2, ...
  Shift	Shift
  Control	Ctrl
  Alt	Alt
  Windows	Windows
  Enter	Enter
  Escape	Esc
  -	Minus
  =	Equals
  [	Open_Bracket
  ]	Close Bracket
  /	Slash
  '	Quote
  ;	Semicolon
  Caps Lock	Caps Lock
  `	Back Quote
  Arrow keys	UP, RIGHT, DOWN, LEFT
  Numeric keypad arrows	KP_UP, KP_RIGHT, KP_DOWN, KP_LEFT
  Numeric keypad digits	NUMPAD0, NUMPAD1, ..., NUMPAD9
  Home	HOME
  End	END
  Page Up	PAGE_UP
  Page Down	PAGE_DOWN

  |

  Note that capturing the space bar is not possible because the drive station interprets this as an emergency stop.

• To use this code, you must initialize NetworkTables:

  import edu.wpi.first.networktables.NetworkTable;
  import edu.wpi.first.networktables.NetworkTableEntry;
  import edu.wpi.first.networktables.NetworkTableInstance;
  
  // Initialization
  
  NetworkTableInstance networkTableInstance = NetworkTableInstance.getDefault();
  if (networkTableInstance.isConnected()) {
    NetworkTable inputTable = networkTableInstance.getTable("inputTable");
    if (this.inputTable != null) {
      NetworkTableEntry upKey = inputTable.getEntry("Up")
      NetworkTableEntry downKey = inputTable.getEntry("Down")
      NetworkTableEntry leftKey = inputTable.getEntry("Left")
      NetworkTableEntry rightKey = inputTable.getEntry("Right")
      NetworkTableEntry zKey = inputTable.getEntry("Z")
      NetworkTableEntry xKey = inputTable.getEntry("x")
    }
  }

• Then during your polling loop, you can do something like this:

  if (upKey.getBoolean(false)) {
    // Drive robot forward
  } else if (downKey.getBoolean(false)) {
    // Drive robot backward
  } else {
    // Stop robot
  }
  
  if (leftKey.getBoolean(false)) {
    // Turn robot counterclockwise
  } else if (rightKey.getBoolean(false)) {
    // Turn robot clockwise
  }
  
  if (zKey.getBoolean(false)) {
    // Raise arm
  } else if (xKey.getBoolean(false)) {
    // Lower arm
  } else {
    // Stop arm motors
  }

TODO

• Add a Gradle build script so that we can pull the latest NetworkTables JAR the same way FRC robots do: ./gradlew build.
• Bring the batch file back to make this JAR easier to run.
  • The distribution created by ./gradlew build includes a batch file.
• Add a section to this README describing how to read the NetworkTablesInput values from the robot code (as soon as we verify that this code works.)
• Don't hard-code the team number; make it -- or, rather, the IP address that uses the team number -- configurable.