Vehicle Interface

1. Vehicle Interface Already substantial electronic information available from the vehicle itself: • Engine status – temp, RPM, diagnostic codes,... • Transmission – what gear are we in? 4WD on/off • Car traction control – are wheels slipping, are we really moving? • Wheel speed/odometry – how far have we moved? how fast? All of this can be utilized with little additional effort. • Throttle also already electronic

2. These inputs come in a variety of forms— Digital: • Straight pulses, e.g. from wheel encoders • As wheel turns, a digital line pulses to indicate revolution • Tens to thousands of ticks/rev → Read with a counter circuit • Serial data: car’s onboard computer, OBD-II → Read with a dedicated decoder interface • A bit-code: transmission position • e.g. “0110” for park, “0111” for drive → Read the digital signal directly

3. Analog: a voltage level of significance • The tension reported by a sensor on the brake line • Resistive load cell produces a voltage proportional to force → Use an Analog-to-Digital converter to read value directly • The voltage sent to throttle the car → Use a Digital-to-Analog converter to create the desired voltage

5. Other thoughts