Power Supplies and Communication Protocols

Jun 27, 2024
DALL E 2024 06 28 11 02 13

Understanding Communication Protocols for Electronic Equipment

Communication protocols are sets of rules that allow two or more systems—or subsystems—within electronic equipment to communicate information. Electrical engineers at original equipment manufacturers (OEMs) or contract manufacturers (CMs) use these protocols to define the rules, syntax, semantics, and synchronization of communication, as well as potential error recovery methods.

Understanding these protocols is essential for the teams responsible for designing products that incorporate power supplies. These include not only electrical engineers, but systems architects, hardware engineers, product managers, software (and firmware) engineers, and even the customers or clients themselves.

Here we'll explore some common communication protocols, and their advantages and disadvantages.

UART Communication Protocol

Universal Asynchronous Receiver/Transmitter (UART)

UART, or Universal Asynchronous Receiver/Transmitter, is a protocol that facilitates the exchange of serial data between two devices using two wires. It is a simple, point-to-point communication protocol often used for short-distance communication.

Despite being an older technology, UART remains widely used but has been supplanted in some applications by newer technologies like SPI, I2C, USB, and Ethernet.

UART can be configured for three communication systems:

  1. Simplex: Data is sent in one direction only
  2. Half-Duplex: Both sides can send data, but not simultaneously—only one side can transmit at a time
  3. Full-Duplex: Both sides can send data simultaneously

Typical communication rates for UART are around 250 Kbps with a maximum distance of approximately 50 feet. UART operates at voltage levels of 0 to 3.3V or 5V.

RS232 Standard

RS232 is a standard that defines the voltage levels for logic 0 and logic 1 in UART serial communication.

It specifies a logic 0 as a voltage between +3V and +15V, and a logic 1 as a voltage between -3V and -25V. RS232 interfaces typically use a 9-pin D-Subminiature (DB9) connector. The standard supports a maximum distance of 49 feet at 9.6 Kbps, and at shorter distances, it can achieve speeds of up to 115.2 Kbps, with some hardware supporting up to 921 Kbps.

RS232 is valued for its simplicity, ease of use, and wide adoption. It uses straightforward wiring, and supports point-to-point communication. As a well-established standard since the 1960s, RS232 is compatible with many legacy systems. Because it operates over a wide voltage range, it has good noise immunity, and is used in diverse applications like computer peripherals, industrial automation, and embedded systems.

RS232 supports both hardware and software handshaking, ensuring reliable data flow. Though not the fastest protocol, it suffices for low-speed communication up to 50 feet. It's cost-effective, durable, and serves as an excellent tool for debugging, testing, and educational purposes. Its continued support for legacy equipment makes it indispensable in many environments.

Extended UART

Extended UART is a half-duplex communication protocol that builds on the core functionality of standard UART, offering additional utility. This protocol enables single-wire and bi-directional communication, allowing for simpler and more efficient data transmission needs, such as monitoring and controlling multiple machines using software.

The Cosel PCA series power supplies use Extended UART for monitoring operational status and changing various set values. It enhances real-time remote control capabilities.

This protocol improves the overall management of power supplies and other devices, making it a versatile and powerful tool for applications requiring precise control and monitoring. Its ability to integrate seamlessly with existing UART systems ensures compatibility while offering advanced features for enhanced functionality.

More details can also be found in the Cosel PCA series Extended UART manual.

Inter-Integrated Circuit (I2C)

I2C, or Inter-Integrated Circuit bus, is a simple two-wire, half-duplex serial protocol used for inter-IC communication. It employs two signals—a clock line (SCL) and a data line (SDA)—

Each device is identified by a 7-bit address, and the master device initiates and terminates all transmissions.

The Inter-Integrated Circuit (I2C) protocol is notable for its simplicity and versatility, making it ideal for inter-IC communication. It uses just two half-duplex lines—a serial data line (SDA) and a serial clock line (SCL)—regardless of the number of devices on the bus. This makes for efficient communication between multiple devices with minimal wiring. Each device on the bus has a unique address, and the master device controls the communication, which simplifies network management.

I2C is common in consumer products and supports multiple target devices on a communication bus. Typical maximum communication rates range from 100 Kbps to 400 Kbps, with a high-speed version at 3.2 Mbps. Typical bus lengths are 9 to 12 feet, though the maximum distance depends on the speed and bus capacitance.

Because I2C supports multiple masters and slaves, complex device configurations are possible and help improve redundancy and flexibility in system design. The protocol supports various communication speeds, typically ranging from 100 Kbps to 3.4 Mbps, accommodating both slow and fast peripherals.

I2C is widely used in consumer electronics, industrial systems, and embedded applications due to its robustness and ease of implementation.
It is suitable for short-distance communication, typically up to a few meters, which is ideal for connecting sensors, displays, and other peripherals in a compact space. Additionally, I2C's ability to handle multiple devices with different speeds and its open-drain design, which prevents bus contention, make it a highly practical and efficient communication protocol.

Serial Peripheral Interface (SPI)

SPI is a widely used protocol for transmitting data between a microprocessor and peripheral ICs, such as memory. SPI operates in full-duplex mode at speeds up to 10 Mbps with a maximum cable length of 10 feet.

The Serial Peripheral Interface (SPI) communication protocol is known for its simplicity, speed, and full-duplex capability, making it ideal for high-speed data transfer between a master device and multiple slave devices.

SPI uses four lines: MISO (Master In Slave Out), MOSI (Master Out Slave In), SCK (Serial Clock), and SS (Slave Select). This setup allows for fast, synchronous data exchange, with typical speeds reaching up to 10 Mbps and even higher in some implementations.

SPI is advantageous due to its low overhead and minimal protocol complexity, enabling efficient and straightforward communication. It supports multiple slaves through individual SS lines, which allows for scalable designs. The protocol's full-duplex nature means data can be transmitted and received simultaneously, doubling the effective communication speed.

SPI's flexibility in clock polarity and phase settings helps tailor the communication to specific peripheral needs, making it highly adaptable. It's widely used in applications requiring rapid data transfer, such as memory devices, sensors, and display modules. Additionally, SPI's simplicity and efficient data handling make it a popular choice in embedded systems and microcontroller projects, providing reliable and fast communication with minimal hardware requirements.

System Management Bus (SMBus)

SMBus is an open-standard protocol for monitoring and controlling system components such as temperature sensors, smart batteries, and power supplies in personal computers. SMBus operates at speeds up to 100 Kbps with a maximum distance of 6 feet, supporting low-speed data transfer with high reliability.

SMBus is a derivative of the I2C protocol, designed for efficient communication in monitoring and controlling system components like temperature sensors, smart batteries, and of course, power supplies.

SMBus is particularly useful in managing the health and status of systems, such as laptops and servers, by enabling communication between the motherboard and various peripherals. Its ability to handle multiple devices on the same bus makes it ideal for complex system management tasks.

Additionally, SMBus includes features like packet error checking and clock stretching, enhancing data integrity and ensuring accurate communication even in electrically noisy environments. This makes SMBus essential for robust system management and control in consumer electronics and computing devices.

Power Management Bus (PMBus)

PMBus is another open-standard, digital-power-management protocol for communicating with power converters or other connected devices. It is a variant of SMBus, based on I2C, but specifically developed for power supply monitoring and control. PMBus typically operates between 100 Kbps and 400 Kbps with a maximum distance of 40 inches.

The Power Management Bus (PMBus) protocol is an extension of the SMBus protocol specifically designed for the digital management of power supplies. PMBus enables precise monitoring and control of power converters and other power-related devices, providing real-time data on voltage, current, temperature, and other parameters. Operating typically between 100 Kbps and 400 Kbps, PMBus allows for efficient communication and control in power management applications.

PMBus's flexibility is one of its key advantages.
It supports both standard and custom commands, allowing manufacturers to tailor it to specific device requirements. This adaptability makes it ideal for use in a wide range of applications, from data centers and telecommunications to industrial and consumer electronics.

The protocol's ability to facilitate detailed monitoring and fine-tuned control helps optimize power efficiency, improve system reliability, and reduce downtime. By enabling proactive power management, PMBus contributes to the development of more energy-efficient systems. Its open standard nature ensures broad compatibility and interoperability among different devices and manufacturers, making it a valuable tool for modern power management solutions.

Controller Area Network (CAN Bus)

CAN Bus, or Controller Area Network Bus, is an open-standard protocol widely used in automotive and industrial applications, including vehicles, trucks, buses, agricultural equipment, and industrial automation. Designed for high-speed data transfer, CAN Bus supports communication rates of 1 Mbps (Classical CAN) or 5 Mbps (CAN FD), with cable lengths ranging from 40 feet to 1600 feet.

CAN Bus is notable for its robustness, reliability, and efficiency in communication, especially in automotive and industrial applications. Its differential signaling provides strong noise immunity, making it suitable for electrically noisy or demanding environments. (See Blink Marine's line of beautifully illuminated CAN Bus keypads and switches for marine, truck, heavy equipment, and automotive applications!)

CAN Bus allows multiple microcontrollers and devices to communicate without a host computer, enabling decentralized control systems. Each device, or node, can send and receive messages, with a unique identifier prioritizing critical data. This prioritization ensures timely transmission of essential information, enhancing system reliability.

The protocol’s error detection and correction mechanisms significantly reduce data transmission errors, improving overall communication reliability. CAN Bus is widely used in vehicles for connecting various subsystems, such as engine control units, airbags, and antilock braking systems. It's also prevalent in industrial automation, medical equipment, and building automation due to its efficiency and robustness.

RS422 Standard

RS422 communication protocol is a high-speed, 4-wire serial communication protocol operating at speeds between 100 Kbps and 10 Mbps, with cable lengths from 50 feet to 4000 feet. RS422 is valued for its high-speed data transfer, noise tolerance, and long-distance suitability. Operating at speeds between 100 Kbps and 10 Mbps, RS422 supports cable lengths from 50 up to 4,000 feet, making it ideal for industrial environments.

It uses a differential current drive output that minimizes electromagnetic interference, ensuring reliable data transmission over long distances. It supports only one transmitting device and up to 10 receiving devices in a network, allowing for effective multi-drop communication.

The protocol's robustness and simplicity make it a preferred choice for applications like industrial automation, where reliable long-distance communication is crucial.

Overall, RS422's combination of high speed, long-distance capability, and noise resistance provides a reliable and efficient solution for many industrial communication needs.

RS485 Standard

RS485 is a robust serial communication standard that does not specify a connector type, but often uses terminal blocks or DB9 connectors. It supports data rates of up to 10 Mbps at 40 feet and 100 kbps at 4000 feet. RS485 is widely used for its ability to operate over long distances and in electrically noisy environments.

RS485 communication protocol is notable for its robustness, versatility, and ability to support long-distance and high-speed data transfer. Operating at speeds up to 10 Mbps over distances up to 4,000 feet, RS485 is ideal for industrial environments where reliable communication is essential. Its differential signaling provides excellent noise immunity, making it suitable for electrically noisy settings.

RS485 supports multi-point communication, allowing up to 32 devices on the same bus, enabling complex network configurations. It is widely used in industrial automation, building management systems, and other applications requiring reliable and efficient data exchange.

The protocol's flexibility in connector types (e.g., terminal blocks, DB9) and its ability to operate in half-duplex mode make it adaptable to various use cases. Overall, RS485’s combination of high speed, long-distance capability, noise resistance, and multi-device support makes it a valuable protocol for many demanding communication environments.

Table: Communication Protocols for Power Supplies

Want a larger version of the table "Communication Protocols for Power Supplies"? Download the PDF

Cosel Power Supplies with Communication Protocols

Cosel offers various products that use these communication protocols to enhance monitoring and control of power supplies in your applications.

Cosel's PCA series

PCA Series

The PCA Series power supplies use either Extended UART or PMBus to monitor or control 63 different functions. These include monitoring AC input, DC output, and current. Voltage can be adjusted from near zero to 120% of the rated voltage, and the PCA series can operate in constant current mode for battery or capacitor bank charging.

Additional digital features include remote ON/OFF, delayed start, and ramp rate control. With medical safety approval, the PCA series is versatile for various applications. 5-year warranty is included.

Cosel's AME series

AME Modular/Configurable Series

The AME Modular/Configurable series utilizes PMBus to monitor and control each module's functions. Configured to meet exact requirements, the AME series, with medical safety approval, is ideal for applications needing multiple outputs and specific power and control features. 5 year warranty is included.

Where to Go Next...

For more information on power supplies from Cosel, please contact ArKco Sales at (651) 777-7454, or arkco@arkco-sales.com.

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