bno055-python-i2c

Python module for the Adafruit BNO055 on the Raspberry Pi connected through I2C.

Getting started procedure

These steps are for the a Raspberry Pi 2 running Ubuntu 14.04 (Trusty). The equivalent steps for Raspbian are well documented by Adafruit and others.

Installing Kernel support

Open this file

sudo nano /etc/modules

and add the followings lines to it

i2c-bcm2708 
i2c-dev

Install the necessary python modules

sudo apt-get install python-smbus
sudo apt-get install i2c-tools

python-smbus is the python module that we use for I2C communication on the Raspberry Pi.

Test it

Connect your i2c peripheral and run this in the shell

sudo i2cdetect -y 1

Corrupted data issues

If you notice that you have bad data (randomly fluctuating data values) coming from the device, it may be due to the I2C clock speed. First check what is the baudrate of the I2C bus using

sudo cat /sys/module/i2c-bcm2708/parameters/baudrate

I have noticed the following behaviour of I2C by varying the baudrate

Baudrate	Behaviour
400KHz	Bus fails to initialize, instead get IOError
100KHz	Bus initializes and device communicates with ~50% data corrupted
70KHz	Bus initializes and device communicates with occasional data value corrupted
50KHz	Bus initializes and device communicates with no apparent data corruption

You can change the baudrate to 50KHz this way

sudo modprobe -r i2c-bcm2708
sudo modprobe i2c-bcm2708 baudrate=50000