Current and former fighter pilots that are fans of this blog, or perhaps those that play flight simulators, will be familiar with the concept of a heads-up display. These see-through screens display situational information in your field of view inside of a vehicle — a form of augmented reality without a headset. Of course, this concept is very interesting, and as electrical engineer Frank Zhao puts it, “Fighter jets have them, so why can’t I?” There are commercial versions available, but in his mind these all try to do too much, so he created his own.
His device, which uses a programmable LED strip powered by a Teensy 3.2, shows data based on whether the car is moving (speed), stopped (RPM) or off (voltage). The LED strip, an upgraded version of NeoPixels known as “DotStars,” shines from the dash onto the inside of the windshield, surrounded by a shroud to keep other drivers from seeing the LEDs. Importantly, the setup uses a photoresistor to sense the ambient light, and adjust accordingly.
Data for this strip is obtained from the car’s CAN bus, via the OBD-II diagnostic port built into modern vehicles. Zhao found that there is a massive amount of data being passed around his car at any one time, and had to filter the messages that the Teensy received in order to avoid getting bogged down with too much information.