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):
# __3-6V__ (Vcc)
# __SDA__ (Serial Data Line)
# __SCL__ (Serial Clock Line)
# __GND__ (Ground)
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
}}}
and you'll see something like:
{{{
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. No two I²C may share the same address on an I²C bus, otherwise there will be contention.
|| Stock || Brand || Description || 7 bit address || Notes
| 1 | Pimoroni | LTR-559 Light & Proximity | 0x23 |
| 3 | Pimoroni | VL53L1X Time of Flight (ToF) | 0x29 | range 40mm-4m
| 1 | Adafruit | VL6180X Time of Flight Distance Sensor | 0x29 | range 5-100mm
| 2 | Adafruit | HT0740 Big Damn Switch 10A | 0x38 / 0x39 |
| 2 | Pimoroni | 11x7 LED Matrix #1 | 0x75 |
| 2 | Pimoroni | 11x7 LED Matrix #2 | 0x77 |
| 4 | Pimoroni | 5x5 RGB Matrix | 0x74 / 0x77 | 77 will be in conflict with 11x7 #2
| 2 | Pimoroni | [ADS1015 +/-24V ADC 3 Channel|Ads1015AnalogDigitalConverter] | 0x48 / 0x49 |
| 2 | Adafruit | ADS1015 12 bit ADC 4 Channel w Prog Gain | 0x48 - 0x4B (jumpers) |
| 2 | PiBorg | Thunderborg | 0x10 / 0x11 |
| 1 | PiBorg | Ultraborg | 0x36 |
| 1 | Pimoroni | ICM20948 9-DOF Motion Sensor | 0x68 / 0x69 |
| 1 | Adafruit | [BNO055 IMU Sensor|BNO055ImuSensor] | 0x28 / 0x29 |
| 0 | Adafruit | VCNL4010 Proximity Sensor | 0x13 |
| 0 | Adafruit | LSM9DS1 Accel Gyro Mag Temp 9-DOF | 0x1C / 0x1E Accel, 0x6A / 0x6B for Gyro |
| 0 | Adafruit | VL53L0X Time of Flight Distance Sensor | 0x29 | range 50-1200mm (2m on long range)
"Stock" is how many [Murray] has in his robot laboratory as part of exploratory design and development of the [KR01] robot.
!! Links
* [I2C|https://en.wikipedia.org/wiki/I%C2%B2C] on Wikipedia
* [Configuring I2C|https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c] from AdaFruit
* [I2C|https://learn.sparkfun.com/tutorials/i2c] on SparkFun
* [Raspberry Pi SPI and I2C Tutorial|https://learn.sparkfun.com/tutorials/raspberry-pi-spi-and-i2c-tutorial/all]
* [Pi clock-stretching bug|https://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html]
* [Adventures in I2C: clock stretching on the Raspberry Pi|https://www.recantha.co.uk/blog/?p=19880], A good article about the Pi and I2C
* [Raspberry Pi slave library for Arduino|https://github.com/pololu/pololu-rpi-slave-arduino-library], Pololu's library for Pi to Arduino comms via I2c
----
[{Tag Hardware}]