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Thread: Testbench setup?

  1. #1
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    Testbench setup?

    I'm contemplating building a simple (meaning low-cost and easy to construct) set-up on a test-bench that will enable me to interrogate control modules using my VCDS cable. Before I launch into the project in earnest, can anyone provide guiding advice (as proof-of-concept) as to whether this is possible?

    My preliminary thoughts are that I could (hopefully) use a J533 module and an OBDII connector in a stand-alone configuration as the interfacing arrangement to the VCDS cable. Then depending on which control module I want to test, power-up the test-module and hook-up the appropriate CAN high/low lines (whilst leaving the other CAN lines unattached) - see diagram below.

    I suspect that this arrangement will cause all sorts of DTCs, but this aside - will it enable me to interrogate the control module for stuff like adaptation channel settings, coding, SA etc.?

    Other questions are:
    (1) Do I need terminating resistors on the CAN lines - if so which ones (used, or unused, or both)?
    (2) Do I really need multiple pins connected for +12Volts and Earth on the ODBII connector - which pins does the VCDS cable need for power?
    (3) Will I be able to register the test module to the CAN Gateway using the set-up?
    (4) Is there a minimum length of twisted-pair wire needed for the CAN lines?

    If my diagram below is "naively simplistic" (as I suspect that it is) can it be amended cheaply to provide a useable test-bench set-up

    Any comments/thoughts welcomed

    Don

    Last edited by DV52; 04-05-2016 at 10:16 PM.
    VW Golf MkVII (103TSI) my13

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    Quote Originally Posted by DV52 View Post
    I'm contemplating building a simple (meaning low-cost and easy to construct) set-up on a test-bench that will enable me to interrogate control modules using my VCDS cable. Before I launch into the project in earnest, can anyone provide guiding advice (as proof-of-concept) as to whether this is possible?
    It definitely is, I have got a few modules linked together on a bench for a bit of experimentation I'm planning:
    - CAN gateway
    - BCM
    - Instrument cluster
    - RNS310
    - BT module
    - Steering control module
    - MFSW buttons

    Quote Originally Posted by DV52 View Post
    (1) Do I need terminating resistors on the CAN lines - if so which ones (used, or unused, or both)?
    I haven't used any.
    Quote Originally Posted by DV52 View Post
    (2) Do I really need multiple pins connected for +12Volts and Earth on the ODBII connector - which pins does the VCDS cable need for power?
    I'm sure I did for ground. You might want to have both a 12v and switched 12v too.
    Quote Originally Posted by DV52 View Post
    (3) Will I be able to register the test module to the CAN Gateway using the set-up?
    Yup
    Quote Originally Posted by DV52 View Post
    (4) Is there a minimum length of twisted-pair wire needed for the CAN lines?
    Probably, the shortest runs in my setup are 20-30cm.

    I'd definitely recommend grabbing the wiring diagrams for a car which uses similar modules as that'll answer most questions. I haven't got the notes from my loom handy I'm afraid.

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    Verified VCDS User Zenerdiode's Avatar
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    You've pretty much got it nailed there Don. In the 'olden days' of the VAG1551; the vehicle literally powered the test device from pin 16 and 4 for positive and negative respectively. You may also want to add a switch to simulate 'Terminal 15' and have a Terminal 15 to the DLC and another end to connect to the module, as some like to see 'ignition switched off' - as that is when they save stuff to EEPROM.

    1) Not really. If you have to, a 120Ω should suffice
    2) VCDS needs + on 16 and - on 4, but add 5 too
    3) Yep, should be fine.
    4) No, and I don't think you'll exceed the maximum either...

    (You're going 'SA Mining' - aren't you? )
    Last edited by Zenerdiode; 04-06-2016 at 08:02 AM.

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    langers2K, Zenerdiode: Galvanised into action by your helpful suggestions (many thanks for these). I'll get down to the local wreckers and then fire-up the soldering iron!!
    Don
    VW Golf MkVII (103TSI) my13

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    Ross-Tech Employee Sebastian's Avatar
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    Make sure to use a suitable power supply, we found that 5A or more may be needed in some cases to overcome the initial surge some of those module require. Also, personally I find it most efficient in the long run, not to solder onto modules directly but instead use the factory connectors. Many moons ago, one of our distrib and I sat down and looked at simple low-cost options to have a modular testbench setup. We decided to use DB25/LPT connectors, partly because they are dirt cheap and there are existing housings for DB25/LPT switches out there.

    While the first versions still looked crude, they just worked...



    ...and some more professional ones came out of it.



    The most important reason for using factory connectors for the control modules, you can easily swap to different modules if needed and the modules themselves stay physically untouched.

    1) I never found a need to use any resistors on the CANs at all, since the modules themselves are already terminated and an open line will do no harm. If no module is connected at all it will just show as an open circuit in the gateway. If you have one module connected, that is plenty termination to overcome the open circuit detection.

    2) You will likely need a J527 or a J519 to simulate the Ignition/Wake-Up messages, I strongly recommend to add a switch for Terminal 15 as well.

    3) For gateways and possibly ECMs, it should work (except the lack of switched power) - some other modules may require Ignition/Wake-Up messages in order to start talking.
    Last edited by Sebastian; 04-07-2016 at 02:40 AM.
    Sebastian @ Ross-Tech.com // VCDS Rookie since 2003

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    als die Meinung eines Andersdenkenden.«

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    ^^^^ Sebastian: Many thanks for the advice- very much appreciated indeed.

    So, to confirm my understanding and in summary:
    -
    1. make sure that I use a low impedance power supply -inrush current can be high on switch-on for some modules. (Why is that - are these modules intrinsically inductive?)
    2. avoid soldered connections - use connectors where possible to allow-for ease of turn-around of modules (DB25/LPT connectors - what an inspired choice! But why so many pins? Even if the test module was networked across all CAN bus-es, that's only 10 wires? Do these modules use hand-shaking lines in addition to CAN high and CAN low?)
    3. CAN bus termination resistors not needed - good, one less thing to worry-about. (I notice that on your set-up you don't bother to use twisted pairs - does your laboratory environment and the short wire lengths mean that noise cancelling is not a problem for the CAN speeds?)
    4. Install Terminal 15 switch - got it (not sure that I understand your advice about needing a BCM - is this required for bench-testing all/most modules? If so, is there any other way of generating the ignition/wake-up message)?


    Cheers
    Don
    PS: Special thanks for the pictures - adds an extra dimension and it's good to see how the professionals do it! I particularly like the termination box with the OBDII connector and the DB25 sockets at the rear (I assume that the CAN Gateway lives inside the box). Real neat idea -I may borrow the design - if you will allow!
    VW Golf MkVII (103TSI) my13

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    Ross-Tech Employee Sebastian's Avatar
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    1) I never put much effort into looking why some modules required a decent power supply, had a proper one from the beginning and never had the time on my hand to bother. I tend to have 5+ modules on my bench setups at most times, the cool thing about the DB25 setup - you can easily extend it by adding just another box. The maximum amount of modules I had connected were 16 at some point for a training course.

    2) CAN-High/Low for Powertrain, Infotainment, Comfort, Extended, Running Gear makes up for 10 pins - that leaves CAN-Diagnostics and CAN-Instruments which brings us up to 16 pins already. Add Terminal 15, 30, 31 and K1, K2/L and W - 22 pins in use now. On some vehicles, there's a dedicated wake-up line, also there is a special diagnostic line for MOST related components. That's 24 so far. Reality is, our DB25 approach is OK for most of our purposes but for a true remaining bus simulation and additional in- and outputs it won't suffice. Looking at my/our scenario, in those rare occasions we simply ran those additional connections separately. For example if you need to hook up dual ECUs, there are some extra lines between those... It also helps to have one DB25 with open lines/pins to it for testing purposes before one ends up making the actual connectors for a specific module.

    4) Some modules will simply not talk via diagnostics, unless you get them to wake up. Many Audi instrument clusters are like that for example. Other modules only have Terminal 30/31 while 15 is purely virtual (i.e. CAN message), meaning without that message they just won't do you any good. If you got some decent CAN tools and know what to send you can probable generate/send the wakeup/ignition messages yourself without hooking up a J527/J519. I found that in most cases it's most convenient to use what's around, meaning the specific modules that generate the messages anyway - besides it's cheaper to buy and hook up a module than to buy and setup said CAN-equipment...

    P.S.: No, the J533 is never in the box. We need to play with different gateways, therefor having the ability to replace them easily is mandatory. The box itself is pretty much full with parallel wiring for the DB25 connectors.
    Sebastian @ Ross-Tech.com // VCDS Rookie since 2003

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    als die Meinung eines Andersdenkenden.«

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    Ross-Tech Employee Jef's Avatar
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    I'll just leave that here... used one of the Ross-Tech OBDII extension.
    http://store.ross-tech.com/shop/OBDEXT-1A.html

    Soldiered up everything and secured under the cap for the ECM connector, then everything is neatly tapped up and supported. Even touched the zip ties on bench grinder so there are no sharp edges from where they were cut. Not shown are the alligator clips on the power and ground lead.

    For my power supply, I'm using an old computer desktop power supply unit with banana plug post sticking out of it. Something like this:
    https://www.youtube.com/watch?v=b9NhsdiX0mc

    I use this step up for pulling PINs on Immob2 and Immob3 ECMs and instrument clusters.

    I like Seb's suggestion of using the LPT connectors if you want to make something more modular.
    Jef
    Ross Tech Support Team, Alpha Squad
    Auto-Scan, learn it, love it, live it... then check the fuses.

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  14. #9
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    Jeff: I never cease to be amazed at the ingenuity of the folk at Ross-Tech - how does Uwe find all these clever people? I envisage a detector in the front foyer of the RT's Lansdale Office, but instead of detecting weapons, it detects IQ - anyone with a number less than 125 doesn't get admission into the office!

    Thanks for the insight into your way of doing-it. My head is spinning with new ideas - all I have to do now is to find some used control modules that need a good home (at the local wreckers).
    Just a question: Do Component Protection issues arise with test-bench polling and if so, do you have any tips for a rank-amateur?
    Don
    VW Golf MkVII (103TSI) my13

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    Does it's prove my "DubNurd" status, that I REALLY want to do this, but don't really have any use for it currently?

    I like this thread.

    I have pretty much the whole car loom from the A3 donor, so have all the OEM connectors. It'll be YEARS before I get a round tuit though

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