The frontpanel controller is required to provide and consume the data for the control panel at the front of the car. The data (as depicted in "Display" and "Input") are sent to the front panel over a modified RS232 link. The link is modified to provide +12v from the PC power supply. As power is coming from the PC powersupply and ultimately the car battery, I did no optimization for consumption, all the components where selected for convienience and familiarity rather than any other criteria. I am a software engineer, with no formal EE training.
The communications occur at 19200bps, 8 databits, no parity bit and 1 stop bit (8-n-1) giving a character rate of 1920cps. This although not superfast is more than adequate for the data being sent, a 100 character track title will be sent in approximatly 50ms. The circuit as shown below has a 7805 voltage regulator to clean up and provide a very steady 5v for the rest of the circuit, a MAX232 level shifter to translate the RS232 into CMOS logic, a PIC16F876A from Microchip that provides the smarts for the frontpanel, and several discrete components to provide the interfacing required to the car systems. I will address each subsection individually.