I²C

I2C (Inter-Integrated Circuit; pronounced as "eye-squared-see" or "eye-two-see"), alternatively known as I2C and IIC, is a <a href="/facts/Synchronous_circuit/k3yddBIN">synchronous</a>, <a href="/facts/Master%25E2%2580%2593slave_(technology)/8APze020">multi-master/multi-slave</a>, <a href="/facts/Single-ended_signaling/u1FAC18z">single-ended</a>, <a href="/facts/Serial_communication/r5xP7P1c">serial communication</a> <a href="/facts/Bus_(computing)/R45TKwS7">bus</a> invented in 1980 by <a href="/facts/Philips_Semiconductors/naAqdtWq">Philips Semiconductors</a> (now <a href="/facts/NXP_Semiconductors/naAqdtWq">NXP Semiconductors</a>). It is widely used for attaching lower-speed peripheral <a href="/facts/Integrated_circuits/fjn6vg7C">integrated circuits</a> (ICs) to processors and <a href="/facts/Microcontroller/MKrnAhnm">microcontrollers</a> in short-distance, intra-board communication.
The I2C bus can be found in a wide range of electronics applications where simplicity and low manufacturing cost are more important than speed. <a href="/facts/Personal_computer/koaYfNce">PC</a> components and systems which involve I2C include <a href="/facts/Serial_presence_detect/fC0VaTHv">serial presence detect</a> (SPD) <a href="/facts/EEPROM/0yAMFY0I">EEPROMs</a> on <a href="/facts/Dual_in-line_memory_module/Ejh7lpxq">dual in-line memory modules</a> (DIMMs) and <a href="/facts/Extended_Display_Identification_Data/WRY4Fueg">Extended Display Identification Data</a> (EDID) for monitors via <a href="/facts/VGA/8GGsGTSc">VGA</a>, <a href="/facts/DVI/Dpnu9JmB">DVI</a>, and <a href="/facts/HDMI/HuNwzm04">HDMI</a> connectors. Common I2C applications include reading hardware monitors, sensors, <a href="/facts/Real-time_clock/pYeXraUW">real-time clocks</a>, controlling actuators, accessing low-speed <a href="/facts/Digital-to-analog_converter/5loEvAeb">DACs</a> and <a href="/facts/Analog-to-digital_converter/8YYNsMFg">ADCs</a>, controlling simple <a href="/facts/Liquid_crystal_display/8B6xGBEz">LCD</a> or <a href="/facts/Organic_light-emitting_diode/219L1aMJ">OLED</a> displays, changing <a href="/facts/Computer_display/NRaTDFHc">computer display</a> settings (e.g., backlight, contrast, hue, color balance) via <a href="/facts/Display_Data_Channel/2lclVrQm">Display Data Channel</a>, and changing speaker volume.
A particular strength of I2C is the capability of a <a href="/facts/Microcontroller/MKrnAhnm">microcontroller</a> to control a network of device chips with just two <a href="/facts/General-purpose_I%2fO/rIGeu7TW">general-purpose I/O</a> pins and software. Many other bus technologies used in similar applications, such as <a href="/facts/Serial_Peripheral_Interface_Bus/uSCU56eG">Serial Peripheral Interface Bus</a> (SPI), require more pins and signals to connect multiple devices.
<a href="/facts/System_Management_Bus/tKmAhz5l">System Management Bus</a> (SMBus), defined by Intel and Duracell in 1994, is a subset of I2C, defining a stricter usage. One purpose of SMBus is to promote robustness and interoperability. Accordingly, modern I2C systems incorporate some policies and rules from SMBus, sometimes supporting both I2C and SMBus, requiring only minimal reconfiguration either by commanding or output pin use. System management for PC systems uses SMBus whose pins are allocated in both conventional <a href="/facts/Peripheral_Component_Interconnect/n6CGuFvP">PCI</a> and <a href="/facts/PCI_Express/ADhsLCUK">PCI Express</a> connectors.

I²C open-in-new

I²C