Wiki: I 2 C

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	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	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	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 on Wikipedia
Configuring I2C from AdaFruit
I2C on SparkFun
Raspberry Pi SPI and I2C Tutorial
Pi clock-stretching bug
Adventures in I2C: clock stretching on the Raspberry Pi, A good article about the Pi and I2C
Raspberry Pi slave library for Arduino, Pololu's library for Pi to Arduino comms via I2c

Tags: Hardware