UART (Universal Asynchronous Receiver-Transmitter)
is a very common communication protocol, especially in embedded systems, microcontrollers, and low-cost, short-distance data exchange. It is widely used to connect modules like GPS receivers, Bluetooth modules, and for debugging consoles to computers.
While common, it is crucial to understand that it is technically a point-to-point interface rather than a true "bus" like I2C or SPI, as it typically connects only two devices directly (one transmitter, one receiver).
Here are the key characteristics of UART:
- Simple Wiring: Uses only two data lines—Transmit (TX) and Receive (RX)—plus a common Ground.
- Asynchronous: It does not use a shared clock signal to synchronize data. Instead, both devices must agree on a set speed (baud rate) beforehand.
- Widespread Application: It is used in microcontrollers, debugging (serial-to-USB), and communication between sensors and main processors.
- Limitations: It is slower than SPI or I2C and cannot support multiple devices on the same two wires (it is not a multi-drop bus).
Common Variants and Related Standards
- TTL Serial: Logic-level UART used directly between chips on a board.
- RS-232: A classic standard for longer-distance serial communication (formerly common in PC ports).
- RS-485: Allows multiple UART-based devices (multi-drop) to share a pair of wires for industrial applications.