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):

  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
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 (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.

Stock Brand Description 7 bit address Notes
1 Pimoroni RGB Potentiometer 0x0E ‡ uses Nuvoton MS51
1 Pimoroni RGB Encoder 0x0F ‡ uses Nuvoton MS51
2 PiBorg Thunderborg 0x10 / 0x11 † dual motor controller
0 Adafruit VCNL4010 Proximity Sensor 0x13 infrared, 0-200mm range
1 Pimoroni IO Expander 0x18 ‡ uses Nuvoton MS51
2 Pimoroni LSM303D 6DoF Motion Sensor 0x1D / 0x1E †
1 Adafruit BH1750 Light Sensor 0x23 / 0x5C 16-bit Ambient Light Sensor
1 Pimoroni LTR-559 Light & Proximity 0x23 light detection; 0-50mm range proximity detection
3 Pimoroni VL53L1X Time of Flight 0x29 range 40mm-4m; 0x29 conflicts with BNO055
1 Adafruit BNO055 IMU Sensor 0x28 / 0x29 † 0x29 conflicts with VL531X
0 Adafruit VL53L0X Time of Flight Distance Sensor 0x29 range 50-1200mm (2m on long range)
1 Adafruit VL6180X Time of Flight Distance Sensor 0x29 range 5-100mm
1 PiBorg Ultraborg 0x36
2 Pimoroni HT0740 10A Switch 0x38 / 0x39 †
1 Adafruit INA260 Current Sensor 0x40 / 0x41 / 0x44 / 0x45 † up to 4 devices via 2 jumpers
2 Pimoroni ADS1015 +/-24V ADC 3 Channel 0x48 / 0x49 †
2 Adafruit ADS1015 12 bit ADC 4 Channel w Prog Gain 0x48 - 0x4B †
1 Adafruit 9-DOF Orientation IMU Fusion Breakout - BNO085 (BNO080) 0x4A
1 Pimoroni ICM20948 9-DOF Motion Sensor 0x68 / 0x69 †
2 Pimoroni 11x7 LED Matrix 0x75 / 0x77 † 77 will be in conflict with 5x5
4 Pimoroni 5x5 RGB Matrix 0x74 / 0x77 † 77 will be in conflict with 11x7
0 Adafruit LSM9DS1 Accel Gyro Mag Temp 9-DOF 0x1C / 0x1E Accel, 0x6A / 0x6B for Gyro
1 Pimoroni AS7262 6-channel Spectral Sensor (Spectrometer) 0x49 6 spectral channels (450, 500, 550, 570, 600, 650nm)

† 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.

Tags:  Hardware

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