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