UART

UART stands for Universal Asynchronous Receiver/Transmitter. It is one of the simplest and most used means of communications among Microcontrollers, and small embedded peripherals. The most common UART protocol is RS232 (often with TTL levels).

Baudrate
Common Baud rates are:

4800, 9600, 19200 and 115200bps

They are usually in multiples of 1200 but in some cases can go down to 300

Code
UART