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I have an Audi A5 and I want to develop and add a custom interface to the rear window.

I have a 5 metre RGB LED strip which contains individually addressable LED's. I have cut this strip into sections to span the rear window and reconnected. I plan to drive the strip using a Raspberry Pi Zero.

I'm trying to find information of how I can interface the left / right signal indicators, brake and reverse lights into the Pi so that I can drive the strip to show colour coded sequences.

Specifically, I would like to find out how to pick up where the electrical signals can be accessed for:

Left / Right turning indication. Reverse lights. Brake lights.

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  • I'm voting to close this question as off-topic because is more related to interfacing with a computer, or controlling electronic devices, than automotive maintenance or repair.
    – CharlieRB
    Commented Dec 29, 2016 at 15:38
  • @CharlieRB, I need information on the Audi A5 and tomorrow I will visit the local Garage.
    – SPlatten
    Commented Dec 29, 2016 at 15:39
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    Why not tie directly into the sources? If you know where the bulb is which shows the indication, link onto it at the wire which leads to it. When the Raspberry Pi device senses the bulb is lit, it should then be able to light whatever you want it to.
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Commented Dec 29, 2016 at 16:10
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    I found issues on my MINI when looking at brake and tail light interfacing. In searching info on that I ran across Audi information. To my understanding many of the newer cars do not apply a switched direct voltage to the lights. Many use variation of a variable voltage or PWM via a CAN controller. You could interface to the CAN controllers or make an adapter (or buy) one that adjusts to the light control levels. This link may or may not pertain to an A5 AUDI INFO.
    – spicetraders
    Commented Dec 29, 2016 at 18:03
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    By chance do you have a workshop manual for your car or a copy of the schematic? I've been digging around and don't think the A5 has a light control module, but I'm not having much luck with finding a schematic for a 2012 A5, so I'm not positive.
    – dlu
    Commented Dec 29, 2016 at 19:47

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It seems like the most straight forward thing to do would be to connect to the signals driving the lights themselves. They are easy to find (for example you can pick up all of them at the housing for the rear lights, most can come out of one side and then you'd pick up the other one from the other side. Or you could find all of the signals together in the dash. I think the choice depends a lot on where you want to locate the Pi.

I would be inclined to use an optoisolator to protect the Pi from the vagaries of the car's electrical system and to match levels with the Pi's inputs.

If the lights are being controlled by a PWM (pulse width modulation) signal from a CAN controller (as @spicetraders suggested in the comment) – which seems like a serious case of overkill, but perhaps it is a tradeoff in terms of the number of wires that have to be run and the ability to do diagnostics against the cost and complexity of the CAN/PWM approach – you might find it easier to try and pick up the signals at the dash before they reach the various controllers. Or, perhaps we have already reached the point where everything is mediated by a controller…

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  • Thank you, I plan to use PWM code I have written before to control the light sequence and fader levels. With regard to the indicator signals, is it a continuous signal or on and off with the blinking?
    – SPlatten
    Commented Dec 29, 2016 at 18:47
  • It will be a continuous signal coming from the turn signal switch in the column, then an on-off (blinking) signal going to the light – assuming that noting is being run through a controller. Otherwise I'm pretty sure you'd still have a continuous signal from the turn signal switch, but I suppose it could be a momentary signal that is picked up by a controller and then canceled by looking at the steering position sensor…
    – dlu
    Commented Dec 29, 2016 at 18:53

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