You started off reading two ADCs and now you are showing us one signal, with positive and negative excursions.
Decide on the external circuitry before worrying about the coding.
Mike has an important point about the spacing.
The proposed method of communication by eye movements seems very laborious, possibly quite disorienting, and requires close attention to detail.
People have been working on this problem for decades or more. What research have you done about modern methods of using eye movements for communication, and if you think this is better, why?