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Thread: VW OBD-II / CAN Bus interface questions

  1. #21
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    I've been looking into various CAN protocal scan tools, but so far everything i found is a tad too expensive for its own good. Maybe once it gets down to the older OBDII protocol pricing.. ($80-$150)..
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  2. #22
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    Thanks for the info Waynel!
    I'm wondering if anyone has done it in a VW Touareg. It can't be that much different from an Audi.

    I see you used the AC control to connect to the CAN bus. In some cars you can use the OBD2 plug to also connect to the can bus (http://www.intrepidcs.com/vcan/vcanobd.htm). have you tried connecting the can adaptor to your Audi A4's OBD2 plug PIN6 and PIN14 (as seen on the link above)?

  3. #23
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    Thanks Jonee for the info! I didnt know the ODB II had can on the connector, i always assumed it was some proprietary protocol. It will be interesting to see which can bus it is linked up to. the AUDI a4 has 3 can buses. I assume it will be either powertrain or another bus with specific for diag. I'll try to plug it in next time I have some free time..will keep you posted.


    arkadiyp, I was looking into building the final interface using a Microchip pic microprocessor with CAN bus but havent dived that much into it. I'm assuming the pic chip would have a TTL serial port, so you could be able to write some code to put on the pic that relayed info between the can bus and the serial port. Then wire a TTL to RS232 converter (i like the MAXIM max203) from the pic chip's TTL serial port to your computer's rs232 serial port.
    So to do this you would need
    Microchip PIC18F248 (Free Sample from Microchip)
    Maxim MAX203 (Free sample from Maxim)
    Starter kit from Microchip with C compiler (saw some advertised for around $39)

  4. #24
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    Waynel, the new A3 (I'm not sure if it's coming to the US) uses CAN for diagnosis through the OBD2 plug. The older K-Line is still used but only the engine functions are reachable (according to Ross Tech).

    I don't know if this will be the case for your 2003 A4, you might check the voltages on Pin6 and 14 of the OBD2 plud and see if they match the CAN H and CAN L.

    I found a cheaper serial CAN adapter: http://www.can232.com/
    Only 99 Euros (at a dealer in Holland, which is closest to Belgium), haven't tried it though but I will place an order as soon as I have some free time to start disassembling my Touareg.

  5. #25
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    Quote Originally Posted by none
    Ummm, CAN is OBDII compliant.
    OBDII is most definitely dead bar some really crap cars like rover etc.
    TBH can is looking shakey too in its basic state - TTCAN is the way forward and even that will be replaced by fault tolerant TTCAN and its successor is already being proposed in a university in a country that doesnt even have 1 car factory!! (cant say too much here)

    For those of you looking for a CAN to PC interface im just deciding how to release my CAN to USB converter. I may let it go for free: source, pcb and all. Its not too complicated and only 2 IC's

    More info later
    XBOX Civic- dcdc converter, 7.2" touch lcd, Evox, Gentoox, 160 gig hdd, Wlan on the way, Custom Paint job

  6. #26
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    Hope this is usefull: http://www.ghg.net/dharrison/

  7. #27
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    Waynel - did you get the CAN address and data for setting the radio vol/selection/etc. or any of the other items? TIA

  8. #28
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    CAN to USB

    Hello Joc_06,

    I am very interested in your CAN to USB Interface,
    is ist possible to get some schematics a.s.o. from you or have you a Website?


    Regards, Zorc

  9. #29
    phc
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    Quote Originally Posted by Zorc
    Hello Joc_06,

    I am very interested in your CAN to USB Interface,
    is ist possible to get some schematics a.s.o. from you or have you a Website?


    Regards, Zorc
    http://www.canpic.com/canusb.htm $99 CAN to USB

  10. #30
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    Quote Originally Posted by waynel
    I've recently gotten this USB to CAN adapter working with my 2003 A4

    http://www.phytec.com/can/hardware/p...ace/sysusb.htm

    The adapter is expensive (about $300 for the optically isolated model that i got) but i figure it saved me like 16 hours of time vs building one myself using the microchip can enabled microcontroller and it has pretty good software out of the box that lets you watch all of the can messages and send can messages too.

    So far, i've plugged it into the the comfort system bus on the yellow connector behind the AC controller (can high-pin 11, can low- pin 12) and the infotainment bus on the connector behind the Radio (the pins are listed on a label on the radio).

    I connected the high, low, and a ground signal. Not sure if the ground was needed, but connected it anyways just in case.

    So far, after a couple of hours playing with the thing, the results are promising.

    From the confort system bus, i was able to unlock/lock doors, roll up/down the power windows, read the location of the window position, flash the turing blinkers, read the position of the power window switches and blink the anti theft light in the drivers door.

    From the infotainment bus, i was able to read the position of the audio controls on the steering wheel, get the time and date from the instrument panel, get the illumination level of the instrument lights, and read the value of the light sensor on the rear view mirror.

    So far, i havent done any tests with the engine on nor the radio and the AC head plugged in (havent spliced any wires yet). After doig that, i see being able to read the speed of the car, and display custom messages on that LCD in the middle of the instrument panel.

    For most things, figuring out what the messages mean is easy. Like the steering wheel radio controls, you push a button and see a particular message being sent. Then you can send your own message with the same message ID and value and see what happens.
    Hi Waynel,
    sorry for the late reply to this post - i hope this gets through to you. Does the phytec usb unit that you used give you all the relevant CAN identifiers and data for each operation that you describe?
    Dave Bleloch

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