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Serial Communication Protocols

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • Serial communication protocols define how data is transmitted sequentially between devices over a communication link based on standardized rules and conventions.

  • Common serial communication protocols include RS-232, SPI, USB, CAN, I2C, and Modbus.

  • Serial communication protocol selection in PCB design depends on various factors, including data rate, distance, power consumption, and specific application requirements.

USB is a widely used serial communication protocol for electronic devices

USB is a widely used serial communication protocol for electronic devices

Serial communication protocols define how data is transmitted sequentially between devices over a communication link based on standardized rules and conventions. During serial communication, bits are sent sequentially over a single wire or pair of wires. There are several serial communication protocols that are widely used in various applications. The table below lists some of the common ones.

Common Serial Communication Protocols

Protocol

Stands for

Description

RS-232

Recommended Standard 232

RS-232 is a legacy serial communication standard used for asynchronous and synchronous communication between two devices. It specifies the voltage levels, signal timing, and connector pinouts.

RS-422

Recommended Standard 422

With RS422, messages can be sent and received simultaneously on separate lines, but they use differential signals to achieve this. 

RS-485

Recommended Standard 485

RS-485 is a standard for serial communication over long distances and in noisy environments. It supports multi-point communication and differential signaling, making it resistant to interference.

USB 

Universal Serial Bus

USB is used in devices such as keyboards, printers, media devices, cameras, scanners, and mice. USB uses differential signaling to reduce interference and allow high-speed transmission over a long distance.   

UART

Universal Asynchronous Receiver-Transmitter

UART is a hardware communication protocol used for asynchronous serial communication between devices. It is often integrated into microcontrollers and communication modules.

USART

Universal Synchronous/Asynchronous Receiver-Transmitter

Similar to UART, USART supports both synchronous and asynchronous serial communication. It is commonly found in microcontrollers and communication modules as well.

SPI

Serial Peripheral Interface

SPI is a synchronous serial communication protocol that involves a master device and one or more slave devices. It uses multiple wires for communication, including a clock signal, data in, data out, and a slave select.

CAN

Controller Area Network

CAN is a multi-master serial communication protocol widely used in automotive and industrial applications. It supports high-speed communication and is designed for real-time communication in noisy environments.

LIN

Local Interconnect Network

LIN is a single-wire serial communication protocol used in automotive applications for communication between vehicle components.

I2C

Inter-Integrated Circuit

I2C is a multi-master, multi-slave, and bidirectional serial communication protocol. It uses two wires and supports various data rates. It is commonly used for communication between integrated circuits.

Modbus

Widely used in industrial automation, Modbus supports master-slave communication and is used for connecting programmable logic controllers and sensors.

Serial Communication Protocols and PCB Design

The selection of a serial communication protocol in PCB design depends on various factors, including data rate, distance, power consumption, and specific application requirements. Protocols often used in PCB designs include I2C, UART, SPI, and RS-232. Here are some other considerations for serial communication protocols and PCB design.

Component Placement

  • The placement of components related to serial communication, such as microcontrollers, transceivers, and connectors, is essential for efficient signal routing and minimizing signal interference.

  • Proper placement helps in maintaining signal integrity and reducing the chances of crosstalk.

Physical Layer

  • The physical layer of the PCB design involves determining the type of connectors, cables, and signal lines to be used for serial communication.

  • Trace impedance, signal integrity, and noise considerations are crucial for reliable data transmission.

Signal Routing

  • Careful routing of serial communication lines is necessary to prevent signal degradation, crosstalk, and electromagnetic interference.

  • Differential signaling and proper termination techniques may be employed to improve signal quality.

Grounding and Power Distribution

  • Effective grounding is crucial for minimizing ground loops and ensuring a stable reference potential for signal lines.

  • Proper power distribution and decoupling capacitors are essential to provide a clean and stable power supply to serial communication components.

Compliance with Standards

  • There may be specific standards that the PCB design must comply with; ensuring compliance is crucial for interoperability.

Choosing and implementing serial communication protocols in PCB design requires careful consideration of both hardware and signal integrity aspects. A well-designed PCB layout contributes to the reliable and efficient functioning of devices utilizing serial communication.

Cadence Tools Support Digital Projects Using Serial Communication Protocols

Whatever serial communication protocols you choose for your PCB, Cadence's PCB design and analysis software, including OrCAD PCB Designer, can help you realize your digital project. OrCAD is the industry’s best PCB design software with utilities covering schematic capture, PCB layout and routing, and manufacturing.

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