Google Stadia Controller Support in Unity's New Input System (1.2+) With full button mapping. Haptics not supported. You should be able to drag and drop this in your project for Stadia controller support

StadiaController.cs

using UnityEditor;
using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.InputSystem.Layouts;

[InputControlLayout(stateType = typeof(StadiaControllerState))]
#if UNITY_EDITOR
[InitializeOnLoad] // Make sure static constructor is called during startup.
#endif
public class StadiaController : Gamepad
{
    static StadiaController()
    {
        // Match device via Name and Manufacturer
        InputSystem.RegisterLayout<StadiaController>(
            "Stadia Controller",
            new InputDeviceMatcher()
                .WithInterface("HID")
                .WithManufacturer("Google Inc.")
                .WithProduct("Stadia Controller"));

        // OR match device via VendorID and Product ID
        InputSystem.RegisterLayout<StadiaController>(
            "Stadia Controller",
            new InputDeviceMatcher()
                .WithInterface("HID")
                .WithCapability("vendorId", 0x18D1) // Google Inc.
                .WithCapability("productId", 0x9400)); // Stadia Controller *
    }

    // In the Player, to trigger the calling of the static constructor,
    // create an empty method annotated with RuntimeInitializeOnLoadMethod.
    [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
    static void Init()
    { }
    
    public ButtonControl captureButton { get; protected set; }
    public ButtonControl googleButton { get; protected set; }

    protected override void FinishSetup()
    {
        captureButton = GetChildControl<ButtonControl>("captureButton");
        googleButton = GetChildControl<ButtonControl>("googleButton");

        base.FinishSetup();
    }
}

StadiaControllerState.cs

using UnityEngine.InputSystem.Layouts;
using System.Runtime.InteropServices;
using UnityEngine.InputSystem.LowLevel;
using UnityEngine.InputSystem.Utilities;

[StructLayout(LayoutKind.Explicit, Size = 10)]
struct StadiaControllerState : IInputStateTypeInfo
{
    // Because all HID input reports are tagged with the 'HID ' FourCC,
    // this is the format we need to use for this state struct.
    public FourCC format => new FourCC('H', 'I', 'D');

    // HID input reports can start with an 8-bit report ID. It depends on the device
    // whether this is present or not. I don't believe this is present on a Stadia
    // Controller. We don't really need to add the field, but let's do so for the sake of
    // completeness. This can also help with debugging.
    [FieldOffset(0)] public byte reportId;

    // The InputControl annotations here probably look a little scary, but what we do
    // here is relatively straightforward. The fields we add we annotate with
    // [FieldOffset] to force them to the right location, and then we add InputControl
    // to attach controls to the fields. Each InputControl attribute can only do one of
    // two things: either it adds a new control or it modifies an existing control.
    // Given that our layout is based on Gamepad, almost all the controls here are
    // inherited from Gamepad, and we just modify settings on them.

    // The DPad inputs are the same as a PS DuelShock controller.
    [InputControl(name = "dpad", format = "BIT", layout = "Dpad", sizeInBits = 4, defaultState = 8)]
    [InputControl(name = "dpad/up", format = "BIT", layout = "DiscreteButton", parameters = "minValue=7,maxValue=1,nullValue=8,wrapAtValue=7", bit = 0, sizeInBits = 4)]
    [InputControl(name = "dpad/right", format = "BIT", layout = "DiscreteButton", parameters = "minValue=1,maxValue=3", bit = 0, sizeInBits = 4)]
    [InputControl(name = "dpad/down", format = "BIT", layout = "DiscreteButton", parameters = "minValue=3,maxValue=5", bit = 0, sizeInBits = 4)]
    [InputControl(name = "dpad/left", format = "BIT", layout = "DiscreteButton", parameters = "minValue=5, maxValue=7", bit = 0, sizeInBits = 4)]
    [InputControl(name = "dpad/x", format = "BIT", layout = "DpadAxis")]
    [InputControl(name = "dpad/y", format = "BIT", layout = "DpadAxis")]

    // The next 4 bits are empty?

    [FieldOffset(1)] public byte buttons1;



    // These are non-regular to gampads and thus are optional
    [InputControl(name = "captureButton", layout = "Button", displayName = "Capture", offset = 2, bit = 0)]
    [InputControl(name = "googleButton", layout = "Button", displayName = "Assistant", offset = 2, bit = 1)]
    [InputControl(name = "leftTriggerButton", layout = "Button", bit = 2)]
    [InputControl(name = "rightTriggerButton", layout = "Button", bit = 3)]
    // The Stadia Button
    [InputControl(name = "systemButton", displayName = "Home", layout = "Button", bit = 4)]


    [InputControl(name = "start", displayName = "Menu", offset = 2, bit = 5)]
    [InputControl(name = "select", displayName = "Options", offset = 2, bit = 6)]
    [InputControl(name = "rightStickPress", bit = 7)]
    [FieldOffset(2)] public byte buttons2;

    [InputControl(name = "leftStickPress", bit = 0)]
    [InputControl(name = "rightShoulder", bit = 1)]
    [InputControl(name = "leftShoulder", bit = 2)]
    [InputControl(name = "buttonNorth", displayName = "Y", bit = 3)]
    [InputControl(name = "buttonWest", displayName = "X", bit = 4)]
    [InputControl(name = "buttonEast", displayName = "B", bit = 5)]
    [InputControl(name = "buttonSouth", displayName = "A", bit = 6)]
    // Unused Bit?
    [FieldOffset(3)] public byte buttons3;



    // Takes up byte 4
    [InputControl(name = "leftStick", layout = "Stick", format = "VC2B")]
    [InputControl(name = "leftStick/x", format = "BYTE",
        parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5")]
    [InputControl(name = "leftStick/left", format = "BYTE",
        parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0,clampMax=0.5,invert")]
    [InputControl(name = "leftStick/right", format = "BYTE",
        parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0.5,clampMax=1")]

    // Takes up byte 5
    [InputControl(name = "leftStick/y", offset = 1, format = "BYTE",
        parameters = "invert,normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5")]
    [InputControl(name = "leftStick/up", offset = 1, format = "BYTE",
        parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0,clampMax=0.5,invert")]
    [InputControl(name = "leftStick/down", offset = 1, format = "BYTE",
        parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0.5,clampMax=1,invert=false")]
    [FieldOffset(4)] public byte leftStickX;
    [FieldOffset(5)] public byte leftStickY;



    // Takes up byte 6
    [InputControl(name = "rightStick", layout = "Stick", format = "VC2B")]
    [InputControl(name = "rightStick/x", format = "BYTE", parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5")]
    [InputControl(name = "rightStick/left", format = "BYTE", parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0,clampMax=0.5,invert")]
    [InputControl(name = "rightStick/right", format = "BYTE", parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0.5,clampMax=1")]

    // Takes up byte 7
    [InputControl(name = "rightStick/y", offset = 1, format = "BYTE", parameters = "invert,normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5")]
    [InputControl(name = "rightStick/up", offset = 1, format = "BYTE", parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0,clampMax=0.5,invert")]
    [InputControl(name = "rightStick/down", offset = 1, format = "BYTE", parameters = "normalize,normalizeMin=0,normalizeMax=1,normalizeZero=0.5,clamp,clampMin=0.5,clampMax=1,invert=false")]
    [FieldOffset(6)] public byte rightStickX;
    [FieldOffset(7)] public byte rightStickY;


    // Not present on every controller?
    // Takes up byte 8
    [InputControl(name = "leftTrigger", format = "BYTE")]
    [FieldOffset(8)] public byte leftTrigger;



    // Takes up byte 9
    [InputControl(name = "rightTrigger", format = "BYTE")]
    [FieldOffset(9)] public byte rightTrigger;
}

Thanks! 😁

I've noticed that after turning a Stadia controller into bluetooth mode, it works natively with Unity!
(See https://stadia.google.com/controller)

With your scripts, it will display explicit names for the buttons and sticks though.

Great job. Works perfectly fine for me. My Stadia Bluetooth Controller wasn't detected before, not even as a Generic Gamepad.

This worked perfectly out of the box. Thanks man!

Great job. Thank you!