Embedded Firmware Developer (ESP32 / M5Stack) — In-Car Real-Time Fuel Cost Tracker via OBD-II / CAN — Working Prototype

We are building a real-time in-car fuel cost tracker that plugs into any vehicle's OBD-II port. The device uses an M5Stack Core2 microcontroller to read engine data via CAN bus, calculate live trip costs in EUR (like a taxi meter), and track CO2 emissions—all without draining the car battery. It automatically logs trips, maintains a multi-year history, and exports data to microSD as CSV for tax or fleet analysis. The prototype must survive automotive thermal extremes, power loss, and frequent starts/stops. This is market validation for a consumer product targeting the 95% of drivers who want real cost visibility but won't install complex diagnostics. Success is measured by accuracy within 10% after one calibration fill-up, zero data loss through 50 abrupt power cuts, and deep sleep at 2 mA or less.