The Inter-integrated Circuit (I²C) Protocol (pronounced I-squared-C) is a hardware serial interface (or "protocol") intended to allow multiple "slave" components to communicate with one or more "master" components. It used across many microprocessors and microcontrollers, including the Raspberry Pi.

I²C permits sensors and other IO devices to be connected to the controller (and/or each other) with only four wires (or really only two if you don't count Vcc and ground):

1. 3-6V (Vcc, red)
2. SDA (Serial Data Line, blue)
3. SCL (Serial Clock Line, yellow)
4. GND (Ground, black)

The colors listed are those used by Adafruit with their line of STEMMA Qt connectors.

The Pimoroni "Breakout Garden" set of I²C sensors also includes an "INT" (interrupt) pin, AKA "GCLK" or "GPIO4".

To View the Current I²C Devices#

To see what's connected on your Raspberry Pi, type (not including the % prompt):

   % i2cdetect -y 1

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- 14 15 -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- 28 -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- -- 
70: -- -- -- -- 74 75 -- 77  

Known I²C Devices#

Some well known I²C products (mostly a list of tested devices; there are thousands available). No two I²C may share the same address on an I²C bus, otherwise there will be contention.

† jumper selectable ‡ software configurable

"Stock" is how many Murray has in his robot laboratory as part of exploratory design and development of the KR01 robot.

Links#

• I2CContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png on Wikipedia
• Configuring I2CContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png from AdaFruit
• I2CContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png on SparkFun
• Adafruit's I2C Address ListContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png
• Raspberry Pi SPI and I2C TutorialContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png
• Pi clock-stretching bugContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png
• Adventures in I2C: clock stretching on the Raspberry PiContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png, A good article about the Pi and I2C
• Raspberry Pi slave library for ArduinoContent unavailable! (broken link)https://service.robots.org.nz/wiki/images/out.png, Pololu's library for Pi to Arduino comms via I2c