i2cdetect

List active I2C buses

$ i2cdetect -l

$ i2cdetect [i2c_bus]

$ i2cdetect -y [i2c_bus]

i2cdetect [options] i2cbus

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

-l

List available I2C buses

Disable interactive mode (no confirmation prompt)

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

Use SMBus quick write commands for probing

Use SMBus read byte commands for probing

Display functionality of the adapter

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.

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.

i2cget(8), i2cset(8), i2cdump(8), i2ctransfer(8)