“A heads-up display for your car’s windscreen showing your speed and/or heading.
This project is a rebuild of Car HUD - Windscreen Display for Speed & Compass by marcozonca. I really liked the concept. Having a number of 0.8in 4-Digit 7 Segment displays left over from my WeMos Flower Alarm Clock build (I could only buy the displays in lots of 5), this seemed like a good project to use one on. The completed unit measures 97x50x25mm.
Hardware design
To reduce the size of the finished unit, I decided to redesign the circuit to use a MAX7219 display driver and a ATtiny1614 microprocessor. The switches form a voltage divider and are connected to a single pin as a analog signal. Although the 7 segment display contains four digits, only three are used and the other is covered up by the GPS unit. Since the ATtiny1614 is programmed using a UPDI interface, the GPS is permanently connected to the CPU’s RX pin.”