Microcontrollers offer very attractive issues to study computer organization or computer architecture concepts, especially in developing countries: low cost, a lot of information available, a complete computer system in a chip, built in functions that make it easier to build hands on projects with programmable devices. Even more, they offer a chance to understand applications of ubiquitous computing paradigm. This paper presents a brief look at the successful process of introducing microcontrollers using a toy car project (overhauling it) in a computer architecture undergraduate computer science course. Description of hardware and software and some interesting and valuable experiences are commented