This is very barebones, and uses the serial interface to communicate
the status of the "a" controller button being pressed.
I'd like to make this a more interactive/graphical demo.
This also adds ta_parameter_writer; I am not certain if I like this,
but it felt necessary to deal with ta_parameters being either 32 or 64
bytes long--for this reason, a reinterpret_cast to a union is less
attractive (the union members are not a fixed size).
