Explain UART communication protocol.

UART (Universal Asynchronous Receiver/Transmitter) is a serial communication protocol for exchanging data between devices. Key features: Asynchronous - no shared clock signal; uses agreed baud rate (9600, 115200 bps common). Two wires: TX (transmit) and RX (receive), plus ground. Frame format: Start bit (LOW), data bits (5-9, usually 8), optional parity bit, stop bits (1-2). Full-duplex communication possible. Simple hardware implementation. Parameters must match between devices: baud rate, data bits, parity, stop bits. Common uses include debug consoles, GPS modules, Bluetooth modules, and PC communication. RS-232/RS-485 are electrical standards that can use UART protocol.