UART Communication Protocol: How It Works, Applications & Examples

UART (Universal Asynchronous Receiver Transmitter) is a widely used protocol for serial communication. Breaking down the name gives us a clear idea of its functionality: “Universal” implies it can work with any transmitter and receiver, “Asynchronous” means it doesn’t rely on a clock signal for data transfer, and “Receiver” and “Transmitter” indicate the two ends involved in communication. In essence, UART enables devices to exchange serial data without the need for a clock. 

This article dives into the UART protocol, explaining how it works, its applications, and practical examples.

What is the UART Protocol?

The Universal Asynchronous Receiver Transmitter (UART) is a simple communication protocol. That allows two devices to send and receive data asynchronously, without using a clock signal. It uses start and stop bits to mark the data, sending it in serial form through TX (transmit) and RX (receive) lines. UART communication protocol is widely used in microcontrollers, debugging, and automation because it is easy to use, low-power, and reliable.

How does UART Work?

UART communication consists of two main components: a transmitter and a receiver. The transmitter converts parallel data into serial form, while the receiver converts it back into parallel form. Here’s a simplified step-by-step explanation:

• Data Framing: Each data byte starts with a start bit, followed by data bits, an optional parity bit, and one or more stop bits.
• Asynchronous Transmission: Devices must use the same speed (baud rate), like 9600 or 115200, for communication.
• Voltage Levels: A high voltage (3.3V or 5V) means ‘1’, and a low voltage (0V) means ‘0’.
• Full Duplex: Data can be sent and received at the same time using separate TX and RX lines.

Features of UART Communication Protocol

UART offers simple yet powerful features that make it widely used:

• Easy to Use: It is simple and needs little hardware or software.
• Flexible: Works well for short-distance communication and can connect many devices.
• Error Check: A parity bit can be used to detect basic errors.
• Low Power: It saves energy, which is good for battery devices.

UART Protocol in Embedded Systems

In embedded systems, the UART protocol is super common for communication between microcontrollers, sensors, and other gadgets. Its straightforwardness makes it a great choice when you need to send data over short distances. 

Application of UART Protocol

UART is commonly used in applications such as:

• Microcontroller Communication: It's a go-to for connecting microcontrollers with devices like sensors, displays, and various modules.
• Debugging and Programming: A lot of development boards rely on UART communication protocol for debugging and programming, making it easy for developers to send and receive data.
• Wireless Communication: You’ll find UART working alongside wireless modules like Bluetooth and Wi-Fi to help with data transfer. 
• Industrial Automation: In factories, UART helps different devices communicate, including PLCs, sensors, and actuators. 
• Consumer Electronics: Gadgets like GPS modules, RFID readers, and serial displays often use UART for data exchange.

UART Serial Communication Protocol

This protocol is characterized by its simplicity and effectiveness in transmitting data. It is particularly useful in scenarios where high-speed communication is not critical. The protocol's ability to operate without a clock signal makes it versatile for various applications.

UART Protocol Example

To illustrate how the UART protocol works, let’s consider a simple example involving a microcontroller and a temperature sensor.

Example Setup

• Microcontroller: An Arduino board
• Sensor: A digital temperature sensor (e.g., DS18B20)
• Baud Rate: 9600 bps

Implementation Steps

1. Connect the Sensor: Connect the temperature sensor to the microcontroller using the appropriate pins.
2. Initialize UART communication protocol: In the microcontroller's code, initialize the UART communication with the specified baud rate.
3. Read Data: Use the microcontroller to read temperature data from the sensor.
4. Transmit Data: Send the temperature data over UART to a connected device (e.g., a computer or another microcontroller).
5. Receive Data: The receiving device can read the transmitted data and display it or perform further processing.

Sample Code

Here is a simple Arduino code snippet demonstrating Universal Asynchronous Receiver Transmitter protocol communication with a temperature sensor:

Here is the explanation of the above code in a very simple way:

• #include <OneWire.h>: Add the OneWire library.
• #include <DallasTemperature.h>: Add the temperature sensor library.
• OneWire oneWire(2);: Use pin 2 for the sensor wire.
• DallasTemperature sensors(&oneWire);: Make a sensor object on that wire.
• setup(): Runs once.
  • Serial.begin(9600);: Start Serial at 9600.
  • sensors.begin();: Start the sensor.
• loop(): Runs again and again.
  • sensors.requestTemperatures();: Ask for a new reading.
  • float temperature = sensors.getTempCByIndex(0);: Get temperature in °C.
  • Serial.print("Temperature: ");: Print the word “Temperature: ”.
  • Serial.println(temperature);: Print the value and a new line.
  • delay(1000);: Wait 1 second.

In short, it reads the sensor on pin 2 and prints the temperature every second.

Conclusion

The UART communication protocol is a crucial tool in embedded systems, enabling simple and reliable data transfer. Its asynchronous operation, two-way communication, and low power usage make it ideal for microcontrollers, industrial machines, electronics, and wireless devices. Understanding UART allows engineers to design efficient and dependable embedded projects. For a structured learning path, our Embedded Systems Course covers UART communication and other critical protocols.

Frequently Asked Questions (FAQs)