i2c on Radxa Rock

Download and flash this image, it has i2c support already baked in.
Otherwise compile your own kernel with i2c support.

Install i2c tools and add you user to the i2c group:

Connect according to the schematics:

radxa i2c

Then you are good to go:

I2C on Pandaboard

To load the kernel module automatically at boot:

add i2c-dev

Finally add your user to the i2c group to fix permission problems: