I am having some trouble using analogReference() in the Energia IDE. I am trying to change the reference voltage from the internal source (3.3 V) to an external source. I know that in order to do this, according to the Energia reference webpage, you must use the argument EXTERNAL. Whenever I go to verify and compile my code, an error is displayed in the console that states that EXTERNAL is "not declared in this scope." What must I do to fix this issue? Thanks.