The Joystick is very similar to the 'analog' joystick on PS2 controllers (PlayStation 2). The X and Y axes are two 10k potentiometers that control 2D movement, generating analog signals. The joystick also has a button that can be used for special applications, so the entire unit can emit X-Y movement signals in both directions and in the Z direction.
This unit communicates with the MSCore via the GROVE A interface. The I2C address is 0x52, Reading the data transferred from the Joystick, you can obtain the movement information from the Joystick.