-`method`: "data", data has been received on the uart
-`number/end_char`:
- if pass in a number n<255, the callback will called when n chars are received.
- if n=0, will receive every char in buffer.
- if pass in a one char string "c", the callback will called when "c" is encounterd, or max n=255 received.
-`function`: callback function, event "data" has a callback like this: function(data) end
-`run_input`: 0 or 1; If 0, input from uart will not go into Lua interpreter, can accept binary data. If 1, input from uart will go into Lua interpreter, and run.
To unregister the callback, provide only the "data" parameter.