The old (Japanese) screen unit in my JDM car was a Kenwood FGZ204F2 system with 4 ports/ harnesses into the back. As part of a plan to replace it with a home brew build, this post is just the outcome my working out what the various pins do.
Car interface and audio bus ports
Car Interface 16-pin Port (#1)
|1||+B||Always on 12V|
|3||ACC||Typically Automotive (ACC)essory, the second stop on ignition key. Sends power to the old unit.|
|5||CAN-H||CAN H & L are data protocol.|
|6||CAN-L||CAN H & L are also pins on the OBD2 port so guess data coming in here is the same|
|7||IGN||Ignition. Maybe another stop on ignition key?|
|8||PARKING||Goes position when handbrake on. Typically pulled to GND|
|9||REVERSE||Goes poitive when car in reverse...for reversing cam|
|10||SPD||If this is speed, weird that its been given own pin, isolated the CAN data|
|11||ILL(PWM)||Illumination/light? PWM is normally 'pulse width modulation'. Not sure|
|12||ILL(SMALL)||Goes positive when head lights are on (for back lighting of unit)|
The interesting here is the CAN H and L pins. Must be the same data that is going through the OBD2 port, and how the old unit got speed, trip data etc.
I hoped there would be a pin for the external ambient air temperature since that was displayed on the old screen. There is not, so it must come through CAN.
Audio Bus 20-pin Port (#2)
Camera and Navigation Unit
Navigation Unit 13-pin Circular Port (#3)
Going to delete this – think it fed to GPS and some Japanese centric traffic stuff.
Rear Camera 4-pin Port (#4)
An analog video signal. Going to delete this and replace with USB video