struct IS_BTN // BuTtoN - button header - followed by 0 to 240 characters
{
	byte	Size;		// 12 + TEXT_SIZE (a multiple of 4)
	byte	Type;		// ISP_BTN
	byte	ReqI;		// non-zero (returned in IS_BTC and IS_BTT packets)
	byte	UCID;		// connection to display the button (0 = local / 255 = all)
	byte	ClickID;	// button ID (0 to 239)
	byte	Inst;		// some extra flags - see below
	byte	BStyle;		// button style flags - see below
	[B]byte	TypeIn;		// max chars to type in - see below
[/B]
	byte	L;			// left   : 0 - 200
	byte	T;			// top    : 0 - 200
	byte	W;			// width  : 0 - 200
	byte	H;			// height : 0 - 200
//	char	Text[TEXT_SIZE]; // 0 to 240 characters of text
};
If the TypeIn byte is set, then it sends a ISP_BTT back when user types in something