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I’m considering buying a 2007 MK TT with an Audi Concert head unit. To me, it’s absolutely essential that I can swap the head unit with my Sony XAV-1000 CarPlay enabled head unit. However, I’m now worried that this would cause issues with the centre instrument cluster (i.e. it going blank/unable to display correct information). Can someone tell me if these concerns are grounded/their experiences?
Thanks!
 

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No you should be ok you just won't have the option to display the usual data from the oem head unit. You will want a fitting kit with a sony appropriate steering wheel remote interface if you have a multifunction steering wheel and want to retain that functionality.

Oh some people have had problems with the amplifier turn on so make sure the fitting kit covers that. Plenty of info in the knowledge base.
 

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I’m considering buying a 2007 MK TT with an Audi Concert head unit. To me, it’s absolutely essential that I can swap the head unit with my Sony XAV-1000 CarPlay enabled head unit. However, I’m now worried that this would cause issues with the centre instrument cluster (i.e. it going blank/unable to display correct information). Can someone tell me if these concerns are grounded/their experiences?
Thanks!
Worry about getting a nice tt then afterwards you can buy a suitable head unit rather than worrying about reusing one you’ve already got!
 
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The central LCD panel is controlled by the instrument cluster computer but has the capacity to display messages and graphics sent by other units, such as the radio and the navigation system. The messages are sent to the cluster via the infotainment CAN bus. If your head unit has a CAN interface it should be able to display simple text messages on the top two lines of the display e.g. radio station information or CD track number. The old BNS 5.0 could also use the centre part of the display to display navigation graphics e.g. turn direction and distance countdown graphics. If your radio doesn't have a CAN interface then the rest of the displays will work fine (e.g. the warnings and range info).

A possible issue is that the OEM units use a CAN message from the ignition key to turn off/on. The headunit turns on in position 1 and off when the key is removed. The car wiring does not have the normal ACC wire to detect the ignition key state. Some 'fitting kits' include a CAN interface to drive the ACC line but these come at a price. An alternative is to provide your own ACC wire.

As already stated the other common mistake is not to provide a +12V signal from the headunit to turn on the amplifier - the infamous blue wire. Lots of posts about this. I have also heard that some of the later Bose equipped cars also use CAN signals to turn on the amplifier, but a 2007 non-Bose should be a blue wire job.
 

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You won't get any issues but it won't display any radio or nav related information after replacing the HU.

You can get some degree of functionality from the aftermarket radio if you get one that's compatible with Maestro RR...and get a Maestro RR (about $100 USD interface). However the functionality of the RR is pretty limited in these cars and not really all that worth it IMO. (I have one.) The OBD gauges and stuff that I get on my Kenwood unit in my A3 is pretty cool but it's nothing you couldn't do, albiet a bit less elegantly, with a cellphone and a mount and a $5 OBD "dongle" off eBay, etc.

Also whenever I'm in Android Auto mode (which is a lot lately becuase for some reason Spotify stopped working with the wireless Spotify app built into the HU :( ) all it displays in the centre is "Android" instead of any track name. Even when it does display track names (in other modes) the length (# of characters) is very limited anyway. iDatalink could have developed it a lot more but they simply didn't want to put in the money and resources to give more functionality in "old" PQ35 cars. Because of this, a lot of stuff the Maestro RR can do in other cars, (particularly mainstream-over-here stuff like Ford, GM, etc.) is not available in VAG cars with the interface. It does do some stuff, but not very much. It does of course do all the standard CAN interface stuff like power up, reverse signal, retained radio power (after key off), steering wheel controls, etc. so if you were going to spend about $50-60 on a CAN interface and/or steering controls adapter anyway, it's not that badly priced.

Note it seems the XAV-1000 is not RR compatible though. Only two Sony models are--the XAV-9500ES and the XAV-AX210 seem to have had compatibility (also not Euro models may have this removed as iDatalink is more a Can/US thing).
 
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Got me thinking you have 🤔. If there is the info available on that system and how it talks, I could probably knock up a little arduino based unit that could display whatever you program it to take from the canbus on the DIS. In fact someone has probably had a go at this. I need to do some Googling.
 

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Got me thinking you have 🤔. If there is the info available on that system and how it talks, I could probably knock up a little arduino based unit that could display whatever you program it to take from the canbus on the DIS. In fact someone has probably had a go at this. I need to do some Googling.
Yep 100% if you have the ability to program this, it's entirely doable--you basically just have to spoof the data the stock head units would sent over CAN bus. Of course however you need to get that data somewhere to begin with--meaning you'd need to get it out of the aftermarket HU. On HUs that have the iDatalink interface you may be able to get it out of that but would probably require reverse-engineering that interface.

An easier way would just be to get it out of a cellphone via Bluetooth (e.g. what song you have playing on Spotify, etc.) which is easy enough, though of course this would only work for content coming out of the phone to begin with.

Going steps further than that one could send data to change the entire display to show different things, which is exactly what PolarFIS, MFA XP, and FIS-Control, all do.
 

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Writing to the top two lines is easy. Although the DIS will force outside temperature to be displayed on line 2 if it's not on the centre section (A safety feature?). Taking over the centre section is a bit more challenging. This link shows what is involved.
 

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Got me thinking you have 🤔. If there is the info available on that system and how it talks, I could probably knock up a little arduino based unit that could display whatever you program it to take from the canbus on the DIS. In fact someone has probably had a go at this. I need to do some Googling.
My Xtrons HU writes FM frequencies onto the DIS, but that's all. RDS would be an improvement,

There's an Android process running called, unsurprisingly, "Canbus" which must talk to the Xtrons Canbus interface. Presumably, other apps send that process the info to display. There are actually only a few different designs of Chinese Android units, sold under a multitude of brand names. I must have a search of the Android developers forums to see if anyone has reverse-engineered the link between the FM radio app and the Canbus.
 

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Albeit the limited stuff torque provides.
The limitation isn't Torque. Audi only make a limited number of PIDs available to OBDII compliant devices (e.g. Boost Pressure isn't supported by the TT MK2 although it exists as a PID). If you want to read more data then you have to interrogate each ECU the same way VCDS does (way more complicated). The other way is to 'eavesdrop' on the CAN Bus but you need to know the CAN ID (and the encoding format) of the data you want and this info is hard to come by. Also the interesting stuff is on the Powertrain Bus, whereas the DIS is on the Infotainment Bus.
 

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The limitation isn't Torque. Audi only make a limited number of PIDs available to OBDII compliant devices (e.g. Boost Pressure isn't supported by the TT MK2 although it exists as a PID). If you want to read more data then you have to interrogate each ECU the same way VCDS does (way more complicated). The other way is to 'eavesdrop' on the CAN Bus but you need to know the CAN ID (and the encoding format) of the data you want and this info is hard to come by. Also the interesting stuff is on the Powertrain Bus, whereas the DIS is on the Infotainment Bus.
Yeah the PID is there but it reports absolute pressure, not gauge pressure. But even then (subtracting approx. 14.7 psi) I don't think it's correct all the time and just reads some nonsense values IIRC (or what looks like nonsense). I can't remember now but I used to try to display it with OBDLink (I have an OBDLink MX), which is similar to Torque in operation and the hardware is not VAG-specific (it is better hardware than cheap dongles but still it's designed for generic OBD-II).

What it displayed never really made sense IIRC, so it was data that really didn't help to read boost pressure anyway. Interestingly iDatalink used to have boost pressure as a selectable PID in the few VAG cars they support but in later f/w releases they removed it so now you can't even select it as something to display. Pretty sure they did this for the same reason--it didn't output expected numbers for boost, even in absolute pressure.

Indeed one has to use VAG-specific data as you say, to read the boost pressure. Either that or just do what the vast majority of ppl do, and use an external boost gauge in a pod, vent-replacement, etc. TBH I got bored of the boost gauge in my A3 (I've even had it and the pod removed for some time now and haven't replaced it). I basically know what my peak boost is (19-20 psi) and I know how it varies with throttle position. I mean it's useful to see if you suspect you're losing/leaking boost but really it's not that big a deal otherwise. For this reason I opted not to even consider putting a gauge in my TT. TBH oil temperature would be more useful and that's already included in the DIS though unfortunately it only displays momentarily before it exits. Also oil pressure would be nice to see--I'd take that over boost too.

What I think would be way more useful for boost is a light beeping sound whenever you're driving (e.g. speed above 10mph or so) and you have the throttle closed for more than say 4-5 seconds, just to tell you now you're into a lag situation. I mean that might get annoying but having a switch to turn it on/off would be useful as well. The thing is this would indicate when you can expect real turbo lag (not the imaginary "turbo lag" auto journalists and people that don't understand what turbo lag actually is talk about lol). Audible is much more important than visual since you're not driving around staring at a gauge and counting seconds unless you plan on crashing lol. My [VEI] boost gauge does have the ability to produce an audible alarm should something go above/below a set value but it doesn't allow you to set a time it can be that way before alerting, so not really too useful...to me anyway.
 
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