HID Control

Human Interface Devices or HID refers to devices which allow humans to interact with computers, such as gamepads, keyboards and such. Using such devices, we can allow users/drivers to control the operation of the robot.

• API
  • HID
  • Acquiring HID
  • Axis
  • Button
    • Buttons and Actions
  • POV
  • Special HIDs
    • Joystick
    • Xbox Controller

API

HID

The flashlib.core.hid component provides an API to access information from different HIDs which are connected to the robot.

A device for human control is represented by the Hid interface. Such devices have different types of controls on them. Those controls rely different types of information:

• Axes: analog input data with both direction (back/forth) and power (percentage). Represented by the Axis interface.
• Buttons: boolean input data which can either be down or up. Represented by the Button interface.
• POV: (Point of View) direction input data in degrees, representing the direction the control is pointed towards.

Each HID as a different number of these controls.

Acquiring HID

Acquiring an instance of the Hid interface is done via the HidInterface component which is provided from RobotControl and is universally accessible via RunningRobot.getControl().getHidInterface().

Each Hid under HidInterface is represented by HidChannel which is a unique identifier for each different Hid.

HidChannel channel = ...;
HidInterface hidInterface = RunningRobot.getControl().getHidInterface();

Hid hid = hidInterface.newHid(channel);

To acquire an HidChannel instance, it is necessary to be familiar with the specific implementation used for HidInterface. Due to this limitation, there is no universal method of acquiring HidChannel.

Axis

Axis controls are represented by a non-negative integer number (referred to as axisIndex). Each axis has a different index representing it; however there is no guarantee that the indices are sequential in order.

Hid hid = ...
Axis axis = hid.getAxis(axisIndex);

// get the current axis value.
// this will return a value from -1 to 1.
// the value has 2 properties:
// - Direction represented by the sign of the value (+/-). Where positive means forward or right, and negative refers to backward or left (depending on the orientation of the axis.
// - Power represented by the absolute value as a percentage. i.e 0.3 is 30%.
double value = axis.getAsDouble();

The axis interface has additional methods, like:

// Inverts the directions of the axis such that + is now -, and - is now +.
axis.setInverted(true);

Button

Button controls are represented by a non-negative integer number (referred to as buttonIndex). Each button has a different index representing it; however there is no guarantee that the indices are sequential in order.

Hid hid = ...
Button button = hid.getButton(buttonIndex);

// get the current button value.
// this will return a boolean value of either true or false where:
// - true = button is down
// - false = button is up
boolean value = button.getAsBoolean();

Buttons and Actions

In addition to basic functionality, buttons are also a type of Trigger and thus can be used to activate Actions using button.whenActive and other methods from the Trigger interface.

For example:

button.whileActive(new ShootAction());

This snippet will cause the action ShootAction to run while the button is down.

POV

POV controls are represented by a non-negative integer number (referred to as povIndex). Each POV has a different index representing it; however there is no guarantee that the indices are sequential in order.

Hid hid = ...
Pov pov = hid.getPov(povIndex);

// get the current pov value.
// this will return an integer value which can be either:
// - -1 if the POV is not pressed or
// - 0->360 (degrees) indicating the direction of the press.
int value = pov.getAsInt();

Special HIDs

Other than the basic HID interface, there are also specialized types that fit specific devices.

Joystick

A flight joystick, with a single stick in the center, a variety of buttons and a single POV. Such devices are represented by Joystick interface and acquired from HidInterface.newJoystick:

HidChannel channel = ...;
HidInterface hidInterface = RunningRobot.getControl().getHidInterface();

Joystick joystick = hidInterface.newJoystick(channel);

The HidChannel used follows the same rules as with HidInterface.newHid such that a call to newHid with the same HidChannel instance will produce the an Hid interface representing the joystick.

Usage of controls follows the API of Hid. However, there are several enhancements for comfort:

• Joysticks generally possess some similarities in axes available. Thanks to this, it is possible to use the Joystick.getAxis(JoystickAxis) overload, which receives values from the JoystickAxis enum instead of an index. However, some axes will not be represented by the enum, since they are not shared by all joysticks.
• Similarly, the Joystick.getButton(JoystickButton) overload provides easier access to buttons.
• Since joysticks possess a single POV, the Joystick.getPov() overload can be used instead of providing an index.

Xbox Controller

A console controller like the different Xbox controllers and even playstation controllers. Such devices have a specific layout of controls and poses a specialized POV. They can be acquired with HidInterface.newXboxController:

HidChannel channel = ...;
HidInterface hidInterface = RunningRobot.getControl().getHidInterface();

XboxController controller = hidInterface.newXboxController(channel);

The HidChannel used follows the same rules as with HidInterface.newHid such that a call to newHid with the same HidChannel instance will produce the an Hid interface representing the controller.

Usage of controls follows the API of Hid. However, there are several enhancements for comfort:

• Controllers generally possess similar (if not identical) layout of axes. Thanks to this, it is possible to use the XboxController.getAxis(XboxAxis) overload, which receives values from the XboxAxis enum instead of an index.
• Similarly, the XboxController.getButton(XboxButton) overload provides easier access to buttons.
• Controllers possess a single specialized POV called D-PAD. This control is represented in a special Dpad interface and can be accessed with XboxController.getDpad()

XboxController controller = ...
Dpad dpad = controller.getDpad();

// Can be used just like with the normal Pov interface
int value = dpad.getAsInt();

// However, DPADs are special because they have 4 buttons indicating directions. These can be accessed from
// the interface and used just like any button
Button up = dpad.up();
boolean isDown = up.getAsBoolean();
up.whenActive(new SomeActionToRun());