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Serial Communication Protocols 

Posted:04:40 PM November 07, 2023 writer: The Engineering Knowledge


The knowledge of basic component that helps the easy communication between different devices is important. In this tutorial, we will cover the world of serial communication protocol with an understanding of different types, modes of transmission, and related terminologies.

A serial communication protocol is a building block of data transmission in a digital world.  Contrary to parallel communication where many bits are transferred rate same in serial Communication one bit is sent at one time. This protocol is commonly used in computing and telecommunication to provide effective and reliable data transmission.

What is communication protocol?

A communication protocol is a rule and standard that defines how data is transferred and exchanged between different systems in computers or devices. These protocols define the rules of timing, formatting, sequence, and errors found when messages are exchanged between different devices. There is makes sure that accurate, reliable, and effective data is accurate by communication protocols, helping different systems to interpret and understand data exchange. Some examples of communication protocols are TCP/IP employed for internet communication and HTTP used for web browsing. They are helpful for simple communication and data transfer in different digital conditions.

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Types of Communication Protocols

HTTP/HTTPS (Hypertext Transfer Protocol/Secure):

There is data communication done with the use of HTTP on the World Wide Web. It explains how messages are formatted and transferred, and which operation web servers and browsers have to perform in the result of different commands. The secure form of HTTP is HTTPS here communication is encrypted to add a security layer. These protocols are the basics of web browsing, online transactions, and getting data from the site.

TCP/IP (Transmission Control Protocol/Internet Protocol):

TCP/IP is considered as the building block of the is a protocol that helps data transmission between computers through the network. This protocol helps that data packets are sent correctly and for accurate sequence and IP is responsible for addressing and routing packets to their required location. This protocol is used in file transfer, web browsing, etc.

FTP (File Transfer Protocol):

It is a standard network protocol employed for file transfer from one host to another with the use of TCP TCP-based networks like the Internet.  It is used by web developers for uploading files to web servers helping sites to be updated with new updates. .

SMTP (Simple Mail Transfer Protocol):

Emails are sent between servers with the use of SMTP. It works in conjunction with POP3 protocols and IMAP to retrieve emails from mail servers. SMTP is important for email communication helping that messages are delivered to the receiver's mailbox.

DNS (Domain Name System):

It is used for translating user's user-friendly domain names in IP addresses that the computer uses for identification of each other on the network. DNS is important for internet browsing as it helps users access sites with the use of easy-to-remember domain names in place of complicated numerical IP addresses.


It is a wireless communication protocol made helps the short Rane Communication among devices. it is used for the connection of smartphones with headphones, speakers, and other devices. This protocol helps easy exchange of data and media files between devices without any wired connection or using cables.

Wi-Fi (IEEE 802.11):

It is a wireless networking protocol that helps devices connect with the local area network without the use of cables. It is used for accessing the internet at homes, public places, and businesses. This technology helps easy internet connection for phones, laptops, and other wireless operating devices.

SNMP (Simple Network Management Protocol):

SNMP is a protocol used to manage and monitor network devices like routers, servers, and switches. It helps network administrators monitor working, find faults, and configure remote devices make ensure accurate and smooth operation of computer networks.

VoIP (Voice over Internet Protocol):

it helps voice communication and multimedia sessions through the use of the internet. In place, the use of telephones in VoIP transforms voice signals into digital data packets, that are transmitted through IP networks. Different VoIP services like Zoom and Skype have revolutionized voice and video communication with cost-effective solutions

MQTT (Message Queuing Telemetry Transport):

It is less less-weight messaging protocol made for small sensors and mobile devices with high-latency or unreliable networks. It is used in IoT projects, that use sensors and devices for exchanging effectively in constrained environments. It is preferred for IoT communication due to the use of less bandwidth and a publish-subscribe model.

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Transmission Modes in Serial Communication

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Simplex Mode:

There is uni-direction communication done in this mode. In this mode data is transmitted from one device to another but not can get data back to the first device. It is like a one-way street where traffic moves in on one side.  A common example of simple communication is monitors and keyboards. Keyboards send data to the computer and monitors receive data from the computer. This protocol is effective for projects where data have to travel in one direction without any feedback.

Half-Duplex Mode:

There are bidirectional communications done this this mode but not at the same time. If one device is sending data other is waiting to receive data. Citizen band radios mostly used half-duplex communication. There can be a switch between transmitting and receiving modes, helping two-way conversation without both sides talking to each other.

Full-Duplex Mode:

The full-duplex mode does two-way communication at the same time. This mode needed separate communication lines for sending and receiving data, providing continuous and real-time communication. Computer networks and telephones are examples of this mode. In a telephone conversation, both ends can talk and listen at the same time

Asynchronous Serial Communication:

It is a technique where data is transmitted without sharing a clock signal between the sending and receiving ends. In this mode sending and receiving ends define certain baud rates to transmit and receive data. Start and stop bits used for synchronization of transmission make sure that both devices are aware of the data transmission starting and ending. For small-distance communication, this mode is used like RS-232 serial ports.

Synchronous Serial Communication:

In this communication mode, there is a need for a shared clock signal between the devices doing the communication process. Data is transmitted according to the clock signal, helping high speed and more effective communication than asynchronous communication. it is mostly used in high-speed and long-distance data transmission, like industrial automation systems and computer networks.

Clock Synchronization

Synchronous Serial Interface

There is a common clock hard between devices in this module that defines the data transmission timing. This shared clock makes sure that both sender and receiver are synchronized helping them to send and receive data at the same rate. This type of synchronization helps to use it accurately for good high-speed and long-distance data transmission that needs accurate timing to save data loss. Its main advantage is the feature to transmit data at high speed. Devices easily exchange bulk data Fastly and in an effective way, making them best for telecommunication systems, computer networks, and industrial automation. They are reliable since synchronized timing reduces data collisions and errors. However getting and maintaining clock synchronization can be difficult, especially for large-scale systems or networks that have many interconnected devices. Signal propagation delays, Clock skew, and noise can affect the timing, and cause data synchronization problems. To solve these issues advanced clock distribution techniques and signal conditioning mechanisms are used.

Asynchronous Serial Interface

Contrary to synchronous serial communication, asynchronous serial interfaces do not use a shared clock signal for operation. In this mode device is based on predefined features like data bits, baud rate, stop bits, and parity settings for synchronization of their communication. This asynchronous nature offers a high value of flexibility, helping devices with the use of changing clock speeds to communicate with each other.

These interfaces are used in small-distance communication and applications where devices function at different clock frequencies. Such as USB connections, RS-232 serial ports, and different wireless communication protocols. They are flexible but slow interfaces due to the involvement of synchronizing data without a shared clock signal.

It is difficult to ensure accurate timing without a common reference clock in this interface. Mismatched baud rates or improper configuration settings can cause data reception errors. To solve this issue devices, employ start and stop bits to signal the starting and ending of each data byte, helping the receiver to synchronize its clock with the incoming data. Accurate configuring and following communication standards are important to prevent timing-related issues in asynchronous serial interfaces.

Other Terms Related to Serial Communication

Baud Rate:

Baud rate defines the speed at which data is transmitted in a serial communication system. It calculates in bits per second and shows how the signal varies per second. The larger baud rate helps the high-speed transmission. Like baud rate of 9600 bps means that 9600 bits of data transmitted per second are transmitted. it is a basic parameter since it defines the rate at which devices exchange data accurately.


in serial communication defines the structure of data packets. It explains that the starting and ending of every data packet are identified. Normally data packets come with start bits, stop bits, actual data bits, optional parity bits, and additional control bits. Framing is important it helps the receiver to differentiate individual bytes or characters existing in the data stream. Accurate framing makes sure that the receiver can correctly define transmitted data.


It is the coordination of timing between the transmitter and the receiver. Synchronization makes sure that devices are functioning at the same clock rate and helps to define each bit of data starting and ending. In synchronous communication, there is a mutual clock signal is shared by devices make ensure accurate synchronization. In this type of communication, start and stop bits are employed for the synchronization process, devices are enabled with the use of different clock speeds for proper communication.

Error Control:

Error control mechanisms are essential in serial communication to detect and correct errors that may occur during data transmission. Parity bits, checksums, and cyclic redundancy checks (CRC) are common error control methods. Parity bits are used to check for odd or even numbers of 1s in the data, providing basic error detection. Checksums and CRC involve more complex algorithms and are used to verify the integrity of transmitted data. If errors are detected, the receiver can request retransmission or employ error correction techniques, ensuring data accuracy.

Synchronous Serial Protocols: 

These protocols are communication techniques in which data is transmitted between devices in a synchronized way, followed by the shared clock signal. it is the best option for high-speed and accurate data transfer. There is data exchanged based on timing provided by the shared clock in this protocol. it makes sure that data is sent and received correctly making this protocol the best for different types of networking. SPI (Serial Peripheral Interface) and I2C (Inter-Integrated Circuit) are main examples of synchronous serial protocols that are used for the connection of microcontrollers and peripherals devices in embedded systems. The main features of this protocol are speed efficiency, and reliability, so used for modern digital communication.

Asynchronous Serial Protocols:

Asynchronous communication does not need a timing clock. Every device receives and sends distal pulses which define bits of data at an agreed-upon rate. This protocol is also called Transistor-Transistor Logic (TTL) serial, in which the high voltage level is logic 1, and the low voltage is logic 0. Currently used each microcontroller comes with one Universal Asynchronous Receiver-Transmitter (UART) for serial communication. such as  RS422,  RS232, RS485.

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In the world of high-speed digital communication, serial protocols are important that help the simple and easy exchange of data between devices.  Synchronous protocols, having synchronized timing and high-speed features, handle projects that need precision and reliable operation.  They are commonly used in systems where data quality and timing are required. While asynchronous protocols are flexible they are best to handle devices with variable clock speeds. Their compatibility and easy-handle features make them the best to use on different digital projects.

The selection of synchronous and asynchronous serial protocols based on certain features of the application. Engineers and developers must focus on the speed, precision, compatibility, and implementation process when choosing the protocol for a required project. There is continuous advancement in technology, and these protocols adapt to the ever-changing requirements of digital applications. Serial communication protocols continue to be the base of contemporary technology, enabling fast data transfer in computer networks and making sure the connection of devices in smart home setups. It ensures that devices can communicate efficiently and effectively in an interconnected world.

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