I can't use digital ports with my raspberry pi?
I haven't seen the datasheet(*) of the Raspberry' BCM2835 SoC, but I would be surprised if it didn't have digital I/O. I guess the I/Os are configurable for either analog or digital, and input or output.

edit
This document describes the Raspberry/BCM2835 peripherals; on page 90 ff it describes how to configure I/Os for either input, output or one of up to 6(!) alternate functions.





(*) Apparently, Broadcom doesn't really want us to see the BCM2835 datasheet, since we have to a fill in an information request form to get at it. Not for me.