GO-EV Car Share is a community car share scheme who own a fleet of electric vehicles for hire to residents, local and visiting businesses on the Isles of Scilly. They needed a seamless solution to allow users to swipe an NFC card on the dashboard to start/end a hire session, as well as track fleet statistics and flag diagnostic issues centrally. After unsuccessfully trialling a commercial solution, they came to me with a list of requests for a custom hardware platform.
Design
This was a complex IoT project involving reverse-engineering the Nissan Leaf CAN bus to obtain odometry, state of charge, tyre pressure data, as well as remote door lock/unlock, as well as a dense PCB with lots of RF components. The spec called for a very low idle current draw (to avoid discharging the 12V battery on the car) so battery voltage detection and intelligent power-up/power-down of each sub-module was necessary.
The hardware itself is on a circular PCB, with a ring of 16 multicolour LEDs and a custom-printed diffuser for a ‘swirly’ UI and intuitive status lights for: processing, error/refused, successfully locked/unlocked.
On the PCB is a SIMCOM 4G / GNSS module, supporting Beidou, GPS, Glonass, an 838MHz LoRaWAN antenna for telemetry on areas on the island without 4G coverage, and a WiFi/BT chip for close-range communication and automatic OTA firmware updates (pushed by the server).
The NFC part is a custom circular antenna design capable of over 8cm range (as it needs to be tapped through the windshield), matched to an MFRC522 NFC chip.
The firmware handles NFC, OTA firmware update, LoRaWAN / WiFi telemetry, firmware lock/unlock, with support for SMS or 4G failover when equipped with a SIM card.
A dozen boxes have worked seamlessly for close to 2 years’ uptime, with no device reboots necessary.
Roles
- Hardware, firmware (C) and mechanical design
- George Goldberg: Back-end, server side software and web UI
Year
2022-
