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Welcome to the Fingerprint_Scanner-TTL wiki!
The intention of this fork is to make changes to the library to allow use of the extra hardware UART serial ports found in Arduino boards like Leonardo and Mega.
Why change to hardware serial?
Sometimes software serial, as implemented in the master library, cannot communicate reliably with the GT-511C1R fingerprint scanner.
Why did the master library use SoftwareSerial?
Most Arduino boards, like the popular Uno, have one hardware serial port, and it is used to communicate with a host computer, both to load programs to the board and to communicate troubleshooting or operational messages back and forth. Therefore, to communicate simultaneously with the fingerprint scanner, we had to use the SoftwareSerial libary to communicate with a standard serial protocol on different pins.
How does Leonardo or Mega communicate with the computer if not through their UART serial port(s)?
The Leonardo and Mega 2560 boards have USB built-in, and so present a virtual serial port to the host computer, freeing their UART port(s) for other uses.
The original Mega board does not have USB built-in, but it does have four UART ports.
See http://arduino.cc/en/reference/serial