Google Stadia Controller is changing with Tandem Mode on Chromecast. This is a new Stadia feature, which changes the USB-c on the wireless Stadia Controller into an input.
When you link your Stadia Controller wirelessly to Stadia, you can plug a secondary controller directly into its USB-C port. When you press buttons on the secondary controller, it will act as though the primary controller’s buttons are being pressed. This is called Tandem Mode. You can use either controller to play games on Stadia, or both at the same time.
This is an early experimental version of this feature that is intended to expand the input device options for Stadia players. A limited set of controllers are currently supported, including the Xbox Adaptive Controller, the Stadia Controller, and some models of the Xbox One and DualShock 4 controllers.
Tandem Mode improves Stadia accessibility by offering more flexibility. With Tandem Mode you can use an alternate controller, such as the Xbox Adaptive Controller when playing on Chromecast Ultra.
When playing with your Stadia Controller wirelessly on any supported screen, you can also use the second controller at the same time to better accommodate your accessibility needs, either by yourself or collaboratively with a second player. Tandem Mode complements other accessibility features.
The steps to use Tandem Mode:
- Turn on your primary Stadia Controller.
- Connect your Stadia Controller to the screen you want to play on, using the screen’s linking code.
- Make sure the secondary controller is charged and turned off.
- Using a USB cable, connect the secondary controller to your primary Stadia Controller’s USB-C port.
Overall currently Google Stadia introduce Tandom Mode with Chromecast on Android.
Source: Google support