Need help - mpg display

[manalar]

I want to build a instantaneous mpg display for my 2007 Toyota Corolla using Arduino Uno and a 7 segment display. I am trying to "extract" the code that deals with instantaneous mpg calculation from obduino32K.pde and I need help (i am not C expert ).

I believe most of the core logic is in get_icons (calculates instantenous mpg), accu_trip and get_pid; however there is so much extra logic to support other features that I am struggling . Any inputs/pointers is much appreciated.