AtTiny Analog to Digital Converter utilizing internal analog comparator with a resistor and a capacitor only. Fully working C version of http://www.atmel.com/images/doc0942.pdf
You may need to check the right R/C value for your clock rate and the circuit diagram from this document.
- Assembly code http://www.atmel.com/Images/avr400.zip
Has several flows. Details are described on C code comments.
- AtTiny2313