Make or buy a RC circuit?

gdsports:
Is it not possible to use an I2C DAC?

Great Idea!
I just bought this:

What fist bewilders me is which output channel from the Arduino I use as Input to the DAC.
I think the DAC want I2C (SLC/SDA) as input, but how do I provide/convert a given PWM (say 3V d=60%) to I2C.

A0 is the analog (flat/smoothed) output, right?