Assuming I have some sort of 3.3v Cmos device which I must use with other 5v devices , lets say via I2C , would i simply, very crudely , just have to drop each connection of the I2C to 3.3v and step up to 5.5v when going the other way. If for some reason i just wanted to make a level converter with separate components instead of an IC designed for that purpose, I am just trying to get an idea of what is going on in there.
No, I2C just uses pull down signaling, so you need to only use pull up resistors to 3V3 and to change a line in the wire library to stop the internal pull ups being enabled.
If you want true level shifted bi-directional coms that circuit will do it for you. The chances are that the 3.3v signals will trigger the 5v side just fine but I like that circuit, it's simple and effective. Made up a few little PCBs that can breadboarded easily and have two channels each. Perfect for I2C.