UART Universal Asynchronous Receiver Transmitter

Emily Lee

Uart Block Diagram

A UART, short for Universal Asynchronous Receiver Transmitter, is a critical piece of hardware for serial communication. It allows devices to exchange data in an asynchronous format, which means the transmitter and receiver clocks are not synchronized. This is a flexible way to send data because it doesn’t require the sending and receiving devices to share a clock signal.

UARTs are widely used in computing and embedded systems to facilitate serial communication. They work by configuring data format and transmission speeds to match the requirements of the devices they are connecting. Data transfers occur bit by bit, with each piece framed by start and stop bits to manage timing without the need for a shared clock, making UART an efficient tool for simple serial data exchange.

Image Credit: Sebastian Lange, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

Unraveling the Mystery of UART: A Simple Guide

UART, which stands for Universal Asynchronous Receiver/Transmitter, is a hardware communication protocol used for transmitting data between devices. It’s a simple, low-cost, and widely used method for serial communication.

What is UART?

UART is a type of serial communication, meaning it transmits data one bit at a time. It’s asynchronous, meaning there’s no clock signal to synchronize the data transmission. Instead, the sender and receiver agree on a data rate (also known as baud rate) beforehand.

How Does UART Work?

UART uses two wires for data transmission:

  • TX (Transmit): Sends data from the transmitting device.
  • RX (Receive): Receives data at the receiving device.

Data is sent in packets called frames. Each frame consists of:

  • Start bit: Signals the start of a new frame.
  • Data bits: The actual data being transmitted (usually 5 to 8 bits).
  • Parity bit (optional): Used for error checking.
  • Stop bit(s): Signals the end of the frame (usually 1 or 2 bits).

UART Applications

UART is used in a wide range of applications, including:

  • Embedded Systems: Connecting microcontrollers and sensors.
  • Industrial Automation: Communication between PLCs and HMIs.
  • GPS Modules: Transmitting location data.
  • Automotive: Communication between various electronic components.

Pros and Cons of UART

ProsCons
Simple and easy to implementLimited data rate and distance
Requires only two wiresNo error checking unless parity bit is used
Widely supported by hardwareSusceptible to noise interference
Low costNot suitable for high-speed applications

UART vs. Other Protocols

UART is often compared to other serial communication protocols like SPI and I2C. While UART is simpler and requires fewer wires, it’s slower and lacks advanced features like addressing multiple devices on the same bus. SPI and I2C are better suited for applications that require higher speeds and more complex communication.

Understanding UART Settings

To establish successful UART communication, both the sender and receiver must agree on the following settings:

  • Baud Rate: The speed at which data is transmitted (bits per second).
  • Data Bits: The number of bits used to represent each character (usually 5 to 8).
  • Parity: The type of error checking to be used (none, even, odd).
  • Stop Bits: The number of bits used to signal the end of a frame (1 or 2).

By understanding the basics of UART, you can leverage this versatile communication protocol for a wide range of projects and applications. It’s a valuable tool for anyone working with electronics, embedded systems, or industrial automation.

Key Takeaways

  • UART stands for Universal Asynchronous Receiver Transmitter.
  • It allows asynchronous serial communication between devices.
  • It configures data formats and transmission speeds without a shared clock.

Fundamentals of UART Communication

The concept of UART is crucial in the digital communication between devices. It enables the exchange of data in a format that systems can understand and process.

Understanding UART Configuration

UART configuration is a set of rules that dictate how two devices communicate over UART protocol. Key setup includes baud rate, data bits, stop bits, and parity.

  • Baud Rate: Rate at which information is transferred in bits per second (bps).
  • Data Bits: Size of the data packet; typically 5 to 9 bits.
  • Stop Bits: Bits sent at the end of every data packet to signal the end; usually one or two bits.
  • Parity: An error checking method. It can be none, even parity, or odd parity.

The UART Data Transmission Process

The UART communication follows a step-by-step process ensuring data moves smoothly from sender to receiver.

  1. The transmitter sends a start bit, which triggers the receiver to listen.
  2. It then sends the data frame: data bits, parity bit if used, and stop bits.
  3. The receiver waits for the start bit, reads the incoming data, and checks for errors.
  4. A handshake may occur for flow control if necessary to prevent data loss.

Electrical signaling in UART uses voltage levels to represent bits:

  • Logic High (usually +3 to +15 volts) for binary ‘1’
  • Logic Low (usually -3 to -15 volts) for binary ‘0’

The TX pin on the sending device connects to the RX pin on the receiving device. The correct voltage level transmission ensures the data integrity during the process.

Hardware and Electrical Signaling

UART hardware in embedded systems bridges communication between microcontrollers and peripherals such as modems.

  • Microcontrollers have UART hardware or software capabilities to manage serial transmission.
  • Transmitters (TX) and receivers (RX) manage outgoing and incoming data, respectively.
  • Logic levels, translating between TTL logic and RS-232, RS-485 standards as needed.
  • Synchronization relies on matched baud rates between devices to prevent framing errors.

Electromagnetic interference is minimized with proper shielding, ensuring data is not corrupted during transfer.