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3.3.4 I2C Usage Instructions

Last Version: 10/09/2025

This section explains how to use the I²C (Inter-Integrated Circuit) protocol to communicate with peripheral devices on the Bianbu Robot development platform. Examples use Python’s smbus2 library, which is recommended for its compatibility and performance.

Prepare I²C Tools​

Clone the I²C debugging tool repository with the following command:

git clone https://gitee.com/cookieee/blue-bridge-cup-hardware.git ~

Tools are located in ~/blue-bridge-cup-hardware/dev-tools/i2ctools, and include the following utilities for detecting and controlling I²C buses:

  • i2cdetect
  • i2cget
  • i2cset

I²C Pin Reference​

Before wiring any device, check the Pin Definition Document to confirm which pins on your board support I²C.

Example: MUSE Pi Pro

  • Available buses: i2c-3 and i2c-4
  • Pin-out shown below:

MUSE Pi Pro I²C pins

Check Available I²C Buses​

Navigate to the tool directory and list all detected I²C buses:

cd ~/blue-bridge-cup-hardware/dev-tools/i2ctools
sudo ./i2cdetect -l

Sample output:

i2c-3	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-1	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-8	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-4	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-2	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-0	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-9	i2c       	spacemit-i2c-adapter            	I2C adapter
i2c-5	i2c       	spacemit-i2c-adapter            	I2C adapter

Hardware Connection & Device Scan​

Hardware Connection​

Connect your I²C peripheral as follows:

Peripheral PinBoard Pin
SDAI²C DATA
SCLI²C CLOCK
VCCPOWER
GNDGROUND

Scan for Devices​

Once connected, scan a specific bus to verify that the device is detected:

sudo ./i2cdetect -yr 4

Parameters:

  • -y Skip confirmation prompt
  • -r Perform a read-only scan (optional)
  • 4 Bus number (i2c-4 in this example)

Sample output:

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

A valid device is detected at address 0x68.

Example: Control Devices with Python​

It is recommended to use the smbus2 library. Install it with:

pip install smbus2

The following example demonstrates how to read device register data via Python:

from smbus2 import SMBus

bus_number = 4           # Corresponds to i2c-4
device_address = 0x68    # Device address
register_address = 0x00  # Register address

with SMBus(bus_number) as bus:
    data = bus.read_byte_data(device_address, register_address)
    print(f"Value read from register {register_address:#02x}: {data:#02x}")

Please make sure that the I2C device node has read and write permissions:

sudo chmod a+rw /dev/i2c-4

Sample output:

Value read from register 0x00: 0xCF

Important Notes​

  • Each I²C device on a bus must have a unique address to prevent conflicts.
  • Some peripherals require initialization or configuration — refer to the datasheet for details.
  • Use smbus2 instead of the legacy smbus library for better performance and compatibility.