This Auxiliary Dash Display Pulls Data From the Car’s CAN Bus
Frederico Souza Sant’ana has taken advantage of his OBD-II port to add an auxiliary data display to his car’s dash.
Cars in the past used simple analog wiring for electronic systems, but all modern cars have a CAN (Controller Area Network) bus. The CAN bus lets the various computers and microcontrollers in a car communicate with each other through a simple shared network, which dramatically reduces the complexity of the wiring harness. Instead of having to wire each and every system to every other system, data can be sent via the shared CAN bus. That data can be accessed, which is exactly how a mechanic checks fault codes through the OBD-II (On-Board Diagnostics) port. Frederico Souza Sant’ana has taken advantage of that to add an auxiliary data display to his car’s dash.
If you have a newish car, then its CAN bus carries a great deal of information that you don’t normally get to see. As an example, your car might not have a tachometer if it has an automatic transmission. But the car’s ECU (Engine Control Unit) still knows how quickly the engine is turning. Sant’ana's OBD Dash Display can show the engine RPM along with many other data points. His car does have a tachometer, but the OBD Dash Display can show whatever information he wants to see.
The OBD Dash Display monitors the car’s CAN bus via the OBD-II port. A common and inexpensive ELM327-based Bluetooth OBD reader is used to connect to the CAN bus. Instead of connecting via Bluetooth, Sant’ana has tapped into the reader with an Arduino Nano board. The data is then displayed on a small OLED screen mounted just behind the steering wheel. He currently has it setup to show the battery voltage, engine RPM, MAP (Manifold Absolute Pressure), spark advance timing, intake temperature, coolant temperature, and throttle position. If you’re interested in car hacking — or just want to have access to more information about how your car is running — then this is a great project to take a look at.