While it’s hard to beat analog instruments for instantaneous automotive feedback, Finnish electrical engineering student Jussi Ristiniemi also wanted a digital speed readout on his 2002 Audi TT.
His particular model normally uses the car’s controller area network (CAN) to transmit the radio station or CD track to the uppermost section of the digital display. For this speedometer mod, audio data was replaced with “KM/H” readings, supplied by the vehicle’s CAN bus system via an Arduino Nano and custom interface shield.
Speeds can now be nicely shown in the center of the instrument cluster, letting the driver know exactly how fast they’re traveling. As it’s winter in Finland, and the TT is only driven during the summer, actual speed display has yet to be tested. However, with access to the car’s full CAN bus, any necessary tweaks should be trivial.