One of the main issues I have come across with planning a Pi-based install has been power-based, and wondering what the best way to trigger a safe shutdown and avoid corruption to the OS.

There are boards that allow for a constant powering directly from the battery that monitor the ignition pin and send a command to the Pi to trigger a safe shutdown when the power goes, and I aim to replicate that function using an arduino.  Kinda.

The Pi will be connected to the Battery directly using a fused, 5v connection. The arduino will be powered by the 12v ignition power, and both devices will be connected together via their serial pins.

The plan is to have the Arduino send a data packet every five seconds, and the Pi will receive it via a Python script that runs on startup. 

If the Pi does not receive data for 10 seconds, this will be due to the Arduino being powered off by the engine being turned off. This can then trigger a safe shutdown of the Pi.

In order to reset the Pi on startup I'd been to incorporate a switch in the wiring to the Pi, but I would love to think of a solution to allow the Pi to just power up when the engine is started.