Controls

• Description
• HID
  • Game Controller IDs
    • Xbox Controller
    • PS4 Controller

Description

Every robot program that we write has a class named Controls that is used to handle reading input from game controllers and switch panels connected to the driver station. This class inherits from the Mechanism class and functions similar to other mechanisms (process() and resetToMode()). However, the Controls class does not have any controller functions of its own because its purpose is to call the controller functions of all the other mechanisms.

HID

To read input from Human Interface Devices (HID) such as game controllers, switch panels, etc., we can use the frc::GenericHID class. The class is initialized with the slot number of the device that is set in the FRC Driver Station. This class has a number of functions that can be called to get input from the device:

1. GetRawAxis(int axis)
   • This function returns the value of the specified axis. This can be used with joysticks on game controllers to read how much they are pushed in the X and Y directions, and with triggers to read how much they are pressed. Typically this value reads from -1 to 1, although the back triggers on some game controllers read from 0 to 1 instead.
2. GetRawButton(int button)
   • This function returns whether the specified button is pressed or not.
3. GetRawButtonPressed(int button)
   • This function returns true when a button is initially pressed. This is useful for things like toggles, where you want to toggle a value when the button is pressed, but not when it is held down.
4. GetRawButtonReleased(int button)
   • Similar to GetRawButtonPressed(), although it returns true when a button is released instead of pressed.
5. GetPOV()
   • This function returns the angle of the DPad in 45 degree increments starting with 0 at the top and going clockwise. If the DPad is not pressed, this function returns -1.

To determine the IDs of a HID’s buttons and axes, you can use USB Devices page in the FRC Driver Station to see what values change when you press buttons or move axes.

Game Controller IDs

The IDs for the axes and buttons on a game controller are different for each type of controller (Xbox, PS4, Logitech, etc.). You can query the ThunderXboxController and ThunderPS4Controller classes (Homer Example) to get the correct IDs for a specific controller, or use the tables below.

Xbox Controller IDs

Axis	ID
Left X	0
Left Y	1
Right X	4
Right Y	5
Left Trigger	2
Right Trigger	3

Button	ID
A	1
B	2
X	3
Y	4
Left Bumper	5
Right Bumper	6
Back	7
Start	8
Left Stick	11
Right Stick	12

PS4 Controller IDs

Axis	ID
Left X	0
Left Y	1
Right X	2
Right Y	5
Left Trigger	3
Right Trigger	4

Button	ID
Square	1
Cross	2
Circle	3
Triangle	4
Left Bumper	5
Right Bumper	6
Share	9
Options	10
Left Stick	11
Right Stick	12