CH Pro buttons
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The button presses generate the following codes: (these are the four bits
at io port hex 201, high nibble):

Hat left	0011
Hat down	0111
Hat right	1011
Hat top		1111

Trigger		0001
left		0010
Right		0100
Low		1000

Multiple presses are not recognized, the button which is earlier in the
above list will override a button that follows it (you cannot have the
hat in more than one position at a time).