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Discussion Starter #1
Im setting up a little project to fit a raspberry pi and a screen to the car.

I've found one CAN Bus location behind the radio in the yellow mini ISO. Found the Hi, Lo and Ground. However on scanning the CAN Bus, it appears to only give basic internal information, the status of the keys, lights, engine on/off and details for the steering wheel stalk control.

I can't see any other things, and Im looking to try and find the external ambient air temperature at least, and also try and get some car stats and see what I can display on the screen.

Im figuring there must be more than one CAN Bus and I need to try and find them!

Simon
 

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Super fantastic Mod Technical Supremo Nice Guy
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You will need to scan multimedia,,
But be wary ...
Make sure you copy everything down,,, before you change any settings..
(Has your scan, picked all the can bus system fitted in your car???????)
 

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Discussion Starter #3
Ahh. Well this is the question isn't it.

How many CANBUS systems are there in the car? I have only found the one system which reports things that the stock radio might need - ie ignition, key, lights, and steering wheel. I haven't found the other CAN Bus systems yet. I suspect one will be on the OBD connector.

Simon
 

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Super fantastic Mod Technical Supremo Nice Guy
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All the ecus, fitted in your car will run through... ONE ,,,,, and only one canbus...
As they have to communicate with each other
 

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Discussion Starter #5
That may be technically true, but it may not be metaphorically true. I've heard that sometimes there can be three CANbuses in the car, or at least the various gateways for the systems may not allow communication between the various elements. Eg, the Multimedia elements, may not be able to talk to the Engine Management systems and vice versa.

As far as I can tell, I may be connected to the Multimedia bus which is located behind the radio, as that is all the codes Im seeing. Im not seeing anything else. So I need to find somewhere else I can get into the system.
 

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All the ecus, fitted in your car will run through... ONE ,,,,, and only one canbus...
As they have to communicate with each other
Dead Right.
As far as I can tell, I may be connected to the Multimedia bus which is located behind the radio, as that is all the codes Im seeing. Im not seeing anything else. So I need to find somewhere else I can get into the system.
All you have found there is the remote dash controls which is NOT Can, although on some cars the speed can elevate the volume.
As mentioned before, you need to find the diagnostic connector or correct pins on ECU, UCH, EPB (if fitted) Steering lock, Power Board etc.
Don't believe everything you read on the internet. Except Here.
https://en.wikipedia.org/wiki/CAN_bus
ONLY ONE CanBus, BUT there are different Protocols on the bus, often manufacturer specific.
Rather like an Omnibus, carrying loads of people, but some may speak German, French, Chinese, Afrikaans & others may be multilingual Etc.
HTH
 

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Discussion Starter #7
Hmm. If what Im reading isn't CAN, then why do I have four wires, a pink, a brown (3v and 2v roughly) and two white cables - one of which is ground - which seems to match CAN specifications, and why are these "non CAN signals" being read by the PiCAN2 board?

Perhaps it is a CAN system for Multimedia?

Im not just reading stalk control information, Im getting information on engine on, off, lights on, off, key in, out, and even some information while the car is moving - I suspect it may be a form of speed pulse.

Looking over various sites at other peoples experiences, people refer to separate CANBus systems, different protocols, baud rates, Internal CAN, CAN-C Diagnostics, Multimedia CAN etc, TIPM, Gateways. Theres a few people with VW's who complain that the CAN Bus connection on their OBD port seems to prevent transmission of certain information. It wouldn't surprise me if there were protective gateways preventing certain information - like a firewall on a network. Another WIKI I've seen suggest also on the OBD connector, as well as pins 6 and 14, there's 12 and 13 for the Multimedia BUS.

So the question therefore, is how do I get access to all the information I need. To be honest, all I want at the moment, is to read static information such as the ambient external temperature - this isn't the same as the coolant temp or the air intake temp. Anything else I can get would be a bonus, just so I can flash up various things on the screen and smile with glee at my geeky delights.

Perhaps you would be able to tell me where in the car I should splice some wires in to hook into the raspberry pi and how I communicate to all the systems in questions? What's the baud rate? Where do I connect to? Can I access the diagnostic CAN from the connection behind the radio?

Simon
 

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Im not just reading stalk control information, Im getting information on engine on, off, lights on, off, key in, out, and even some information while the car is moving - I suspect it may be a form of speed pulse.


Simon
If you look at your car stereo ..ignition on and stereo gets that information to switch on (unless stereo manually switched off) lights on will dim stereo display and yes movement will be a speed pulse (or a taxi meter installers point of connection to measure distance/speed)
 

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How about this, all canbus wiring will run two wires, one high can, one low can, these wires will be wrapped around each other ( twisted
But the protocol fitted in your car is one canbus..
On your diagnostic socket, pin 6 is high ,, pin 14 is low
 

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Discussion Starter #10
How about this, all canbus wiring will run two wires, one high can, one low can, these wires will be wrapped around each other ( twisted
But the protocol fitted in your car is one canbus..
On your diagnostic socket, pin 6 is high ,, pin 14 is low
Well I know the OBD port is in the armrest on my vehicle, so that's no problem. If I can find the ASR Control unit, I think I might be able to take a feed off here.

But it doesn't really explain how, if this is one canbus, why there are different signals on different ports. Behind the radio, there is exposure to the canbus, however on this segment, I am only seeing multimedia relevent commands.

Im guessing plugging into the OBD, Im going to see diagnostic elements, but I might not see the multimedia. How I gain access to every bit of information on the CAN, the multimedia, the diagnostics, the drivetrain, everything I could possibly need? Do I need multiple feeds?

Also the CAN exposed behind the radio, while being high, low and ground, isn't actually twisted.
 

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Think of the can system as a fuseboard in your house,, you have a power in
and neutral, If you take a fuse out to the lights, the sockets in your house will work,,,
Its basically two busbars..
So when your can system gets to your multimedia, it will read it, but if it is not ALWAYS part of the system, The UCH,, is the fuseboard,, but if it is not told to communicate with the multimedia, for different reasons/fittings, it will ignore it.
IT is As though you have a fuse pulled out
 

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Discussion Starter #12
Ahh.

Now this makes more sense - and what I was trying to get at - probably very badly.

I gather the UCH is the Body Control Module, which is referred to on some diagrams as the ASR.

So the UCH may not communicate to the Multimedia - for very good reasons. I may be able to read more signals by connecting higher up in the chain, such as nearer the UCH. Or I might need a CAN Bus reader here, and a CAN Bus reader for the Multimedia. The Multimedia must get some readings from the CANBus, just not all.

I come from a computing/networking background, so I refer to devices more as firewalls, routers, gateways. I see separate segments of the same network - sometimes even separate networks but interconnected. And not all networks can talk to other networks, as there are firewalls in place controlling what can be sent and received. So my terminology is slightly different :)

But I think we're saying the same thing.

OK, so we've now got the OBD, UCH and Multimedia. So, back to the question, if I want to read all the signals and all the systems, where in the chain do I need to connect in to? Even if that means multiple connections!

Simon
 

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Yes the UCH ( Body control module ), this needs to be informed..
Thats why I gave the original warning, as the configuration settings need to match with the airbag module,, so it is a lot of playing..
If it is not connected on the gateway then no chance,,, you will need to inform the UCH,,
 

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Discussion Starter #14
What does the UCH need to be informed about?

All Im interested in at the moment, is monitoring, to see what's there.

I don't mind playing though.

Just need to know where I need to connect to for every item. Will try the OBD port first as that seems easier.
 

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It has to be informed multimedia is present, though a radio is fitted..
Not quite the same thing..:idunno: why.
But a very nice man with a yellow van , allowed me to play.
He can confirm, just kept coming up configuration error...
That was trying to tell the UCH it was present...
We played with that and the airbag system,,,(matched both sections as present) but because it was not fitted, it would not allow it to be configured, to become part of the network.

So put everything back " AS IS " and left alone ..
While it was still a runner and not a house brick:wink2::grin2:
 
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