After reviewing this I see one of my mistakes was how I interpreted USR_BTN. I thought that was referring to the right most button on the unit. Now I see that it is defining the left button (S1 on the board). That makes more sense now. So the right button which is the reset button I assume cannot be programmed, correct? Its only purpose is to wake the unit up from sleep. So how do I work with the last button, the center button. It is labeled S0. Can this only be used for placing the unit into Flash mode?