i2cdetect

scans I2C buses to detect connected devices

TLDR

List active I2C buses

$ i2cdetect -l

Scan devices on I2C bus 1

$ i2cdetect -y 1

Scan using SMBus quick write commands (safer default mode)

$ i2cdetect -y -q 1

Scan using SMBus read byte commands

$ i2cdetect -y -r 1

Scan all addresses including reserved ones (0x00-0x7f)

$ i2cdetect -y -a 1

Display adapter functionality

$ i2cdetect -F 1

i2cdetect scans I2C buses to detect connected devices. It's commonly used for debugging I2C hardware, identifying device addresses, and verifying hardware connections on embedded systems and single-board computers.The output is a grid showing addresses 0x00-0x7f. Detected devices show their address, while empty positions show "--". Addresses marked "UU" are in use by a kernel driver.On Raspberry Pi and similar boards, I2C is often used for sensors, displays, and other peripherals. Common devices include:- 0x27/0x3f - LCD displays- 0x48-0x4f - Temperature sensors- 0x50-0x57 - EEPROMs- 0x68 - Real-time clocks

PARAMETERS

-l

List available I2C buses

-y

Disable interactive mode (no confirmation prompt)

-a

Scan all addresses (0x00-0x7f instead of 0x03-0x77)

-q

Use SMBus quick write commands for probing

-r

Use SMBus read byte commands for probing

-F

Display functionality of the adapter

INSTALL

sudo apt install i2c-tools

sudo dnf install i2c-tools

sudo pacman -S i2c-tools

sudo apk add i2c-tools

sudo zypper install i2c-tools

brew install i2c-tools

nix profile install nixpkgs#i2c-tools

CAVEATS

Requires root privileges or membership in the i2c group. Scanning can interfere with sensitive devices; use -y carefully in production. Some devices may not respond to detection probes.

HISTORY

i2cdetect is part of i2c-tools, a set of utilities for I2C bus access on Linux. I2C (Inter-Integrated Circuit) was developed by Philips in 1982 and became widely used in embedded systems.