UART Protocol

Introduction

UART stands for Universal Asynchronous Receiver-Transmitter. Unlike protocols like SPI or I2C, UART is not actually a communication protocol in the strictest sense; it’s a physical circuit (usually a standalone integrated circuit or a feature built into a microcontroller) that transmits and receives serial data.

Here is what makes UART unique:

  • Universal: The data format and transmission speeds are configurable.

  • Asynchronous: There is no shared clock signal between the sender and receiver to synchronize the output of bits.

  • Serial: Data is transmitted bit by bit over a single wire, rather than in parallel across multiple wires.

The History of UART

UART is one of the oldest digital communication protocols still in widespread use today.

  • The 1960s (The Teletype Era): The origins of UART trace back to the era of teletypewriters. Early computers needed a way to interface with mechanical teletypes. Gordon Bell, a famous computer engineer at Digital Equipment Corporation (DEC), designed the first UART to interface the PDP-1 computer with teletypewriters. This early UART was roughly the size of a shoebox and built using discrete logic gates.

  • 1971 (The First IC): As integrated circuits (ICs) became available, the massive UART boxes were shrunk down to single chips. Western Digital introduced the WD1402A, widely considered the first single-chip UART. This revolutionized the computer industry by making serial communication cheap, reliable, and compact.

  • 1980s (The PC Era): The IBM PC popularized the 8250 UART chip. This chip became the backbone of the standard serial port (RS-232), which was used for decades to connect mice, modems, and printers to computers.

  • Modern Day: While the bulky external serial ports have largely been replaced by USB, UART is far from dead. It merely moved “under the hood.” Today, almost every microcontroller (like those in Arduinos, smart appliances, and cars) has multiple hardware UARTs built directly into the silicon. It remains the absolute standard for GPS modules, Bluetooth modules, and low-level debugging consoles for software engineers.

UART is incredibly robust, which is exactly why it has survived for over half a century in the fast-moving tech world.

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