Just using this to see where the buttons are mapped to on my controller

CheckInput.cs

using UnityEngine;
using System.Collections;

public class CheckInput : MonoBehaviour {
	
	void Update(){
		if ( Input.GetKeyDown ( KeyCode.JoystickButton0 )){Debug.Log("JoystickButton0");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton1 )){Debug.Log("JoystickButton1");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton2 )){Debug.Log("JoystickButton2");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton3 )){Debug.Log("JoystickButton3");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton4 )){Debug.Log("JoystickButton4");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton5 )){Debug.Log("JoystickButton5");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton6 )){Debug.Log("JoystickButton6");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton7 )){Debug.Log("JoystickButton7");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton8 )){Debug.Log("JoystickButton8");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton9 )){Debug.Log("JoystickButton9");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton10 )){Debug.Log("JoystickButton10");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton11 )){Debug.Log("JoystickButton11");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton12 )){Debug.Log("JoystickButton12");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton13 )){Debug.Log("JoystickButton13");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton14 )){Debug.Log("JoystickButton14");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton15 )){Debug.Log("JoystickButton15");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton16 )){Debug.Log("JoystickButton16");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton17 )){Debug.Log("JoystickButton17");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton18 )){Debug.Log("JoystickButton18");}
		if ( Input.GetKeyDown ( KeyCode.JoystickButton19 )){Debug.Log("JoystickButton19");}
	}
}