#397 I²C Scanner

Scanning for I²C devices with an Arduino.

Build

Notes

This is a simple sketch, inspired by i2c_scanner that simply scans for the presence of addresses in the full 7-bit address space.

This can be very helpful when trying to use I²C modules where the default address is not documented.

About I²C

I²C (Inter-Integrated Circuit) is a communications bus specification invented in 1982 by Philips Semiconductor. Patents on I²C have now lapsed and trademark protection only remains for the logo.

I²C is now generally supported by many manufacturers, but it is also known as TWI (Two-Wire Interface) or TWSI (Two-Wire Serial Interface) Note: in some cases, the term “two-wire interface” may hint at incomplete implementation of the I²C specification.

I²C provides bi-directional communication for many devices in a master-slave configuration over two wires.

I²C addresses are used to select between devices on a single bus. There are 7-bit and 10-bit address modes:

7-bit addresses are most commonly used in microcontroller peripherals
10-bit addresses are not yet widely used, and support is limited
the sketch here only looks for 7-bit addresses

Code

The I2CScanner sketch runs an address scan every 5 seconds and prints the address of any found devices over the serial port.

console

It uses the standard Wire Library to attempt to begin a (null) transmission to each device address. The Wire.endTransmission() return code indicates the status of the transmission:

0:success
1:data too long to fit in transmit buffer
2:received NACK on transmit of address
3:received NACK on transmit of data
4:other error

Any device that returns 0 is reported as a valid address.

Construction

Pull-up resistors may need to be provided if they are not already present on the I²C two-wire bus.

Breadboard

Schematic