The System Management Bus (SMBus) is a two-wire hardware interface that lets system component chips and devices exchange control messages. It is used especially for system and power management, including communication among batteries, chargers, sensors, and other components.
What is the System Management Bus?
The official System Management Bus (SMBus) Specification, version 3.2, defines SMBus as “a two-wire interface through which various system component chips and devices can communicate with each other and with the rest of the system.” In practical terms, it is a low-level control bus: devices use it to send messages rather than requiring a separate control line for every function. The specification identifies reduced pin count and room for expansion as benefits.
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SMBus covers electrical characteristics, network-control conventions, and communications protocols at the physical, data-link, and network layers. It does not define higher-layer system functions, so SMBus is not a computer’s general-purpose internal data bus.
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SMBus was originally intended to link an intelligent battery, its charger, and a system microcontroller that communicates with the rest of the system. Its role is not limited to batteries: the specification also identifies power-related devices, system sensors, inventory EEPROMs, and communications devices as possible participants.
#1 Best Overall
- HiLetgo IIC I2C Serial Interface Module
- Supply Voltage :2.5-6V
- Supports the I2C protocol
- PCB Color: Black
How is SMBus related to I²C?
SMBus is based on I²C operating principles. The ACPI specification describes it as a two-wire interface based on I²C, while the Linux kernel’s I²C and SMBus documentation says SMBus is mostly a subset of I²C protocols and signaling.
That substantial overlap does not establish that every I²C device, controller, or transaction works with every SMBus implementation. For a particular system, check the device and controller specifications and confirm that the required protocol and software support are present.
Rank #2
- I2C LCD Adapter: Support IIC I2C Interface Two lines (SDA and SCL) can control LCDs. The traditional LCD connection method needs to occupy more pins
- Supply voltage: 2.5-6V
- Control with backlight power: Plug in the jump cap to connect the backlight power supply, and unplug the jump cap to disconnect the backlight power supply
- Adjustable contrast: rotate the blue potentiometer, increase clockwise, weaken counterclockwise
- Module can be counted: 8 can be couplet. Modify the device address by short -circuit A0/A1/A2. The default address is 0x27
Which SMBus specification is current?
The System Management Interface Forum’s SMBus specifications index lists version 3.3.1, dated 20 October 2024, as the current release. The definition and scope described above are documented in version 3.2, dated 12 January 2022. Version-specific details from 3.2 should not automatically be treated as details of 3.3.1.
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Best Value
- Supply voltage: 2.5-6V; I2C address: 0X20~0X27 (the original address is 0X20, you can change it by yourself); for 1602 LCD 2004 LCD.
- Wiring instructions: GND--system power supply negative; VCC--system power supply positive; SDA-- IIC data line; SCL-- IIC clock line.
- Come with 2 IIC interface which can be connected by jumper or IIC special cable,If you already have I2C devices in your project, this LCD module actually doesn't cost any more resources at all.It is fantastic for your project.
- It allows you to power the display via two cables and transmit the data with only two connections. The I2C serial bus is very convenient to use and enables efficient and reliable data transmission.
- This practical module offers fast transmission and can convert the parallel data transmission of an LCD display into a serial I2C signal. With the adapter, only 4 instead of 16 connections are required and has an additional 6 selectable IIC addresses, which enables the simultaneous operation of up to 6 displays.
Rank #4
- FOR LCD1602 AND LCD2004 DISPLAYS: PCF8574 I2C adapter module for LCD character screens reduces required IO pins from 7 to 2 for simple wiring.
- PCF8574 I2C IO EXPANSION CHIP: Built in PCF8574 enables stable 8 bit IO expansion through I2C for Arduino, ESP32 and Raspberry Pi.
- ADJUSTABLE CONTRAST AND BACKLIGHT CONTROL: Blue potentiometer adjusts LCD contrast and jumper allows easy LCD backlight power control.
- ADDRESS CONFIGURABLE AND CASCADE SUPPORT: Default address 0x27 can be changed using A0 A1 A2 pads and up to eight modules can be cascaded on one I2C bus.
- WIDE VOLTAGE LCD COMPATIBILITY: Operates from 2.5V to 6V supply voltage and fully compatible with standard LCD 1602 and LCD 2004 character displays.
Rank #3
- 1.The I2C interface is a huge improvement, freeing up a lot of pins on the Arduino for additional functionality. Works fine with the LCD1602 and LCD2004.
- Modules can be cascaded up to eight. The device address can be modified by short-circuiting A0/A1/A2. The default address is 0x27. The default address can be detected by the program.
- The module uses the PCF8574, which enables most MCUs to implement remote I/O port expansion via two bidirectional buses (I2C). The device includes an 8-bit quasi-bidirectional port and an I2C bus interface.
- The contrast is adjustable, and the blue potentiometer is rotated clockwise to enhance, and counterclockwise to weaken.With backlight power control, you can set whether to connect the backlight power through the jumper cap.
- The original LCD1602/2004 screen requires 7 IO ports to drive. This module only needs 2 IO ports to drive, which can save you 5 IO ports.
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