I2C UNO and MEGA for RepRap Prusa i2 control using PS3 controller.

For the last couple of weeks I have been trying to connect a PS3 controller to my i2 however it hasn't been going as well as I though it would.

I thought that using an UNO with the USB Host Shield would be able to communicate with the Mega through I2C and then send G-code to the printer when buttons are pressed on the controller. 

However I am unable to get I2C communication at all, I have tried a few tutorials to no avail, I can get basic sketches to work with the Uno and Mega without Ramps 1.4 attached, but when I but the Ramps board on and use the I2C pins on that, nothing happens.

I have tried setting the Uno slave and Mega Master and vise versa but this still doesn't help.

If anyone has any ideas please leave a comment.