A microcontroller board can talk to the user by using LED display, buzzer, LCD screens etc., and the user can talk back to the microcontroller using switches, keyboard etc. There are few communication methods where the user and microcontroller can have a two-way communication using a single device or medium. The serial port of the microcontroller provides the easiest way by which the user and the microcontroller can write their data in the same medium and both can read each other’s data. When the serial port of the microcontroller is connected to the PC and the incoming and outgoing data is monitored using software and displayed in a window, it forms the simplest text user interface (TUI) setup for the microcontroller.In such a system the user can send the data from the PC to the microcontroller’s serial port using software running in the PC, and can view the data which is send to the PC by the microcontroller in the same software. The microcontroller should have the capability to read the data send by the PC and send the data back to the PC.
The serial communication is the most important communication port which all microcontrollers should have. This enables the user to communicate with the microcontroller using text commands. The microcontroller can also send back data in text format or simply as data bytes. Thus the serial communication provides a text user interface (TUI) for the microcontroller. Apart from simply communicating with the user the serial communication is a very useful debugging tool in the code development process. It can send back the run time status of the internal registers, value of the variables etc. When a given with a microcontroller a developer will first try to make the serial port up and working.