Command to read in digital signal from a connected Arduino board
Board pointer, to indicate which board to use to differentiate one board from another
Digital pin to measure the signal
The Arduino board has a set of logical ports (digital) that are used for writing or reading data from a component.
To map a UNO, ports 2-13 are available (0 and 1 are used for serial transmission). For MEGA board, ports 2-53 are available. The port takes the low logic level (0) or logic high (1) which corresponds to the reference voltage.