Suppose you're using a microcontroller that only has digital inputs (like the ARMexpress appears to be). What would be the simplest/cheapest/easiest way to measure analog signals from such a thing? For example, is there an I2C A/D module that you can query for a value? Or some other gizmo you could communicate with in a digital way?
Basically, I know there are a lot of analog sensors out there, and I'm trying to get an idea of how much grief I'd be causing myself if I choose a controller that lacks analog inputs.