What exactly does it do?
It's an all-in-one solution that plugs right ontop of the Raspberry Pi and it:- Provides a power supply (5 Volts) for the Pi.
- Turns the Pi on at the appropriate time and off again so it doesn't drain your battery when the car isn't in use.
- It has circuitry to talk to the car's bus (IBUS).
- Manages your reversing camera video signal and power supply (optional).
How does it work?
- The ATtiny2313A microcontroller (MC) enables or disables the power (PIEN) for the RPI when appropriate. Unlocking the car will turn it ON and start booting. Six minutes of idle will turn it OFF.
- Q4 allows the MC to ground pin 17 of the TV module - which instantly switches the video on the car's monitor.
- D3 allows the MC to receive from the IBUS.
- D4 allows the RPI to receive from the IBUS.
- Q2, Q3 allows the RPI to transmit on the IBUS.
- The K1 relay selects from two video sources: RPI or Camera and switches +12V on for the Camera when needed.
- The LP2950 provides 3.0 volts and is very efficient to save your car's battery.
Schematic
Parts List
Contact: pete@pibus.info