How To Add Front Park Assist Camera to 2003-2014 XC90
 

I recently acquired a XC90, MY2009.
My car has a builtin rear parking camera, called a PAC (Parking Assist Camera) by Volvo.

I do not have the front parking sensors and so decided to research how I could add a Front Parking Assist Camera (FPAC) to help when parking..

Looking at the wiring diagram, you can see that the rear PAC sends composite analog PAL* (* = to be confirmed) video down a coax cable to the MMI nav computer under the left hand front seat. For LHD, this is the drivers seat. For RHD, the passenger seat.

The video connects to pin 10 of the connector 16X/108B, which is the connector plugged into the MMI (nav DVD HDD drive) unit und the left hand front seat.

Pin 10 then goes to the display DPY, connecting to pin B:10.
The video shield is connected to pin H, the shield connector of the cable.

The DPY connector B has the following pinout:

1: R = RED video signal
2: GN = GREEN video signal
3: VO = Not used
4: P = Serial bus to the display Digital signal Half duplex, startstop synchronizer, 2400 bps. Description of protocol is here: https://github.com/festlv/carpc/blob.../src/rti/rti.h
5: BN = Signal, remote control receiver, from the remote control IR sensor on the display. 38 kHz carrier wave when the remote control is pressed
6: BL = BLUE video signal
7: SB = Video ground
8: Y = Composite video sync for RGB, display screen Analog signal 0-5 V
9: GR = Not used
10: W = reverse camera PAL video input 1 V p-p +/- 0.2 V
H = Shield

The screen is switched from RGB to PAL composite input to NTSC composite input via the serial bus commands on pin 4.


More protocol info here on a Swedish forum:
http://translate.google.com/translat...3254b43e#endif


My Idea So Far
To feed a front camera to the display, we need to have a relay switch the video signal of pin 10 from the rear camera to the front camera

The relay can be switched as follows:
When 12V from the reverse lights is present, the relay turns ON, connecting the rear camera to the display
Otherwise, the relay is OFF, and the front camera is connected to the display
This would allow the reverse camera image when in reverse, otherwise the front camera image. using this switching mechanism would avoid all issues of how to send a data command to the display to force it to switch inputs.

The front camera needs to be powered by 12V only when needed
As the entire camera system is activated by first switching to reverse, the camera power can be fed also from a feed that is active in reverse, and for a few minutes afterwards. This should be sufficient.

This could be a timed power supply fed by the reverse lamps, with something like a 30s to 1min delay before switching off.
The power supply can be a very simple RC circuit powering a relay, or more complex with a timer control.

The rear camera stays on for xx* (* = To be confirmed) seconds when switching out of reverse, and potentially goes off when reaching xx kmph

To Test:
1. Does the picture switch on when a video signal is present OR does it switch when a CAN bus command is sent? All research says it is the data command, but this needs to be confirmed.

2. How long does the rear PAC image stay active?

3. What is the default video format for the rear PAC video signal?

I will be testing and confirming these over the next few weeks, and getting a front camera for testing my theories.

Stay tuned.....

Very interesting.

Although you might program a time delay for the image to remain visible for the front camera, wouldn't the screeen begin to descend as soon as reverse is deselected?

The screen descends only when the rear camera switches off, and that occurs around 15 seconds after deselecting reverse.

My first build will avoid adding any microcontrollers to fool the CAN bus or the display bus - that is often too complex for the average DIYer.

I will attempt using just the reverse lamp feed from a taillight to switch between front and rear camera, and rely on the the 15s delay as the standard display time for the front camera.