Bernie writes: The PIC12F675 looked like a good match for this project. The pair of 10k resistors on GP0 and GP1 are to allow in-circuit programming via a protoclip. RS-232 levels are generated by robbing the negative voltage from the computers transmit line (which is not otherwise used here), and creating usable signal levels from the device to the computer. For schematics and source codes visit the projects page.
PIC12F675 Magnetic Card Reader (for track2 credit cards ): [Link]