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UART Communication: Serial Interfaces Demystified

Universal Asynchronous Receiver-Transmitter (UART) is one of the most common device-to-device communication protocols in use today. It represents the hardware-integrated circuit that is utilized in serial communication, and this is done via the serial port. UART is one of the parts of microcontrollers, but also a standalone integrated circuit.

In this article, you will learn about the basics of UART communication, its working mechanism, applications, advantages, disadvantages, and the key differences between parallel and serial communication. Continue reading to learn more about UART.

What is UART?

UART is short for Universal Asynchronous Receiver-Transmitter, which is also an inbuilt IC found in microcontrollers. Its main function is to facilitate serial data communication within systems, and this is done via parallel or serial data communication.

In simple terms, UART describes a set of rules or protocols that are utilized when exchanging serial data between devices. It only requires two wires between the receiver and the transmitter to enhance relevance and transmission across the two directions.

A key thing to understand about the communication in UART is that it can be simplex, implying that data is sent in a single direction, half-duplex where data is sent in both directions but only one at a time, and full-duplex that allows simultaneous transmission across both sides.

Working Principle of UART

The communication in UART is between two devices which are the receiver and the transmitter. Basically, data is sent by the transmitter to the receiver, and it’s important for each device to have a UART interface. This is to facilitate communication via these protocols. There are three main components within the UART interface and they are the receiver, baud rate generator, and transmitter.

Basically, the role of the transmitter is to take data and information from the microcontroller and convert it into bits, which are then sent out to other electronic components. On the other hand, the receiver accepts bitstreams, which it then converts into bytes of information or data. The baud rate generator is designed to generate signals to control the reception of data and the transmission timing.

Comparison of Parallel and Serial Communication

A single line or cable can be used in transferring data in serial data communication, and this is usually done in a bit-by-bit fashion requiring the two cables. This is not expensive, and it also doesn’t require many wires and circuitry like parallel communication. Another thing to note is that serial data communication is ideal for use in compound circuits.

With parallel communication multiple cables are used in transferring data, and this is done all at once. It is a more expensive option but offers fast transfer of data. It also requires the use of extra cables and hardware. Key examples of this communication include RAM, PCI, and old printers.

Understanding UART Communication

There are two types of UARTs used for UART communication, and they include the receiving UART and the transmitting UART. Basically, communication is directly done between the two UARTs. To enhance communication, there’s a need for cables that allow communication between each UART.

The receiving and transmitting pins also allow data to flow, and this transmission is done asynchronously. It is also done via a data bus, usually as a parallel. Once the parallel data is received, three bits are added to create a data packet, and these bits are start, stop, and parity. The data packet bit is then transformed to the parallel form to facilitate the elimination of the three bits.

Here’s an overview of the three bits:

  • Start Bit: This is a synchronization bit, and it’s usually placed ahead of the main data. In general, it is an inactive line of data transmission controlled within high-voltage levels. For transmission to begin, UART drags the data line from high voltage to low voltage levels.
  • Stop Bit: This is located at the end of the data packet, and it stops broadcasting by maintaining the data line at high voltage levels.
  • Parity Bit: This bit allows the receiver to determine if the collected data will be right or not. It is not a compulsorily used bit, which is why it isn’t commonly used.
  • Data Frame or Data Bits: This is the real data that is transferred from the sender to the receiver.

Applications and Benefits of UART

In general, UART is mostly utilized in microcontrollers, and this is for different requirements. You will also find them in different communication devices, including Bluetooth modules, GPS units, wireless communication, and many other applications.

The most notable benefit of UART communication is that it is easy, reliable, and simple to implement, and this is why it’s a popular option that is employed in many applications. Because it only utilizes two wires for communication, its utilization in cases where there is limited space is further simplified. Its utilization over long distances is also possible because the protocol is robust.

Despite these wide benefits and applications, it’s important to note that there are a few drawbacks associated with UART communication. The main one is that the protocol is relatively slow when compared with other communication protocols like I2C and SPI. Another drawback to note is the fact that it’s not a full duplex protocol. Therefore, data transmission is always done in one direction at a time.


UART represents a universal asynchronous receiver transmitter, and this is a two-wire protocol that is designed for serial data transmission. It is one of the most reliable and simple protocols that is utilized for serial communication across devices. UART communication is widely used in multiple applications, and this is because of its robustness, reliability, and ease of usage.

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