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Thread: Device recommendation needed

  1. #1
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    Device recommendation needed

    Hi there,

    I am totally new to OBDII, CAN, SAE standards and protocols so I would like to start experimenting a bit with it and I am looking for hardware device recommendation.

    So, here is what I expect from my begginers device:

    1. Having SAE J1962 plug so I can connect it directly to the car without any additional cables
    2. Being ELM 327 compatible in terms of configuring things via AT commands or at least to have things configurable to the degree ELM327 has them)
    3. To have bluetooth transmission to host (PC, PDA, cell phone) that works at CAN 11/500 bus speed. So, not 38.4 kbaud to host but full 500kbaud at slowest bottleneck. I expect to have AT command that will change speed of all subsystems.... i.e. if i set speed to 125 kbaud I expect CAN, UART, bluetooth... all are at that speed without bottlenecks.

    Now here are some additional requests where things get quirky and eliminate cheap chinese products:

    4. Possibility to programatically define pins at J1962... in example some vehicles have two CAN buses, namely HSCAN (usually on pins 6 i 14) and MSCAN (pins vary, some have it on pins 3 and 11, other on some other pins) so I want to be able to programatically choose/set/define pins where CAN BUS is, its speed, timeouts, headers, filtering....

    5. Possibility to concurrently sniff two 500kbaud (or maybe 250kbaud + 500kbaud since I guess Bluetooth can't go above 900 something kbauds) buses and concurrently doing some ODB2 requests.

    Since I am really new to all this stuff suggestions are highly appreciated.
    Many thanks in advance.

  2. #2
    VENDOR - ScanTool Vitaliy's Avatar
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    For someone just starting out, you want a lot of stuff.

    If you don't mind me asking,

    1) What are you trying to do?
    2) How much are you willing to pay for such device?
    OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
    Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

    You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

  3. #3
    Variable Bitrate
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    3. You cannot change the speed of the can-bus. That is a) specified by the OBD2/EOBD standard and b) the responsibility of the vehicle.
    5. There's only one bus that responds to OBD2/EOBD requests - the High speed can-bus at pins 6 and 14. The others are not covered in the standards.

    Even if a vehicle has the J1962 compatibly connector, it doesn't mean the car supports OBD2/EOBD.
    That depends on the region where you live (Usa, Europe, Brazil, Australia, Japan or anywhere else) and also on the model year and the type of fuel (petrol, diesel).
    Can maybe present in a vehicle, but the OBD2/EOBD connection may still be one of the older slow protocols.
    Can was not mandatory for OBD2/EOBD until 2008.

  4. #4
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    Quote Originally Posted by Vitaliy View Post
    For someone just starting out, you want a lot of stuff.

    If you don't mind me asking,

    1) What are you trying to do?
    2) How much are you willing to pay for such device?

    1. Gateway/firewall/reemiter between buses.
    2. As little as possible of course. Ideally something like that would be already present on market... really not thinking of custom hardware price range as of now.

    I am begginer in CAN/OBD but not in embedded electronics programming.
    I know how to code DSPs/FPGAs/PIC/other embedded electronics.

  5. #5
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    Quote Originally Posted by p2psmurf View Post
    3. You cannot change the speed of the can-bus. That is a) specified by the OBD2/EOBD standard and b) the responsibility of the vehicle.
    I know I cannot change vehicle bus speed.... these tend to be in 125/250/500 kbps range and are defined by the manufacturer.
    What I can change is the speed of interface to the CAN bus to match it and that's what I've meant.
    So, interface needs to work at 125 kbps for let's say LWCAN/MSCAN or whatever it is called that is for instance on single wire at pin 1 of J1962 connector for Fords or at pins 3 and 11 for let's say Mazdas. I want to be able to set up an interface in a way no matter what are the pins and speeds I can configure interface so it's able "to talk" to that bus without bottlenecks like CAN is working at 500 kbps but is not able to transmit to host at that speed because UART to BT transceiver is dip-switched/hardwired/any other way limited to 38.4kbps.


    5. There's only one bus that responds to OBD2/EOBD requests - the High speed can-bus at pins 6 and 14. The others are not covered in the standards.

    Even if a vehicle has the J1962 compatibly connector, it doesn't mean the car supports OBD2/EOBD.
    That depends on the region where you live (Usa, Europe, Brazil, Australia, Japan or anywhere else) and also on the model year and the type of fuel (petrol, diesel).
    Can maybe present in a vehicle, but the OBD2/EOBD connection may still be one of the older slow protocols.
    Can was not mandatory for OBD2/EOBD until 2008.
    I know all of this too... I did my preliminary homework and did a basic research of standards and since I am trying to learn something new and for the future, I restrained myself to CAN (ISO 15765-4) only as it will be (or already is) the only standard for the future.
    I am not interested in dealing with physical layer of the story but expect device to do that part for me so I can focus on software that would eventually:
    a) Integrate buses and info that comes from them
    b) Log data in real time for analysis and reverse engineering
    c) Do standard part of ODB-II diagnostics (mode 1 to 9) but there are already too many SW solutions for something like that so it will be just a bonus, not the main feature.

    This is something I've planned for stage I, eventual stage II would be to try and actually actively emit my data to the CAN bus for the various purposes but this still looks as pretty distant future.

    So, what I really look for is a hobby priced device that is capable of doing things like that.

    Since I have absolutely no knowledge about how to build hardware, where to obtain chips from, I never soldered a single wire my reasoning goes something like this (apologies if this is incorrect since I am really dummy for this kind of things): Cheap ELM327 1.4 Bluetooth dongle can be obtained via eBay for as little as 18 US$ with shipping. Let's say device needs better BT module instead of dip switched 38.4k so let's just double the price so it's 36 US$ now with decent faster BT. Clone has just one instead of two "CAN receivers" so let's double the price to 72 US$ so device is able to listen/talk to two CANs simultaneously. Let's add additional 28 US$ for the ability to programmatically "rewire" the pins and redo the firmware a bit (to add a couple of more AT commands) and we end up with nice square 100 US$ which is IMHO pretty fair price for the advanced but still hobby device.
    I mean there will be no pass-throughs nor increased voltages and things that make things professional grade... it's a bit more advanced reader/sniffer. that cost 5x the price of a cheap clone.

    p.s. Just borrowed one clone from a local car electrician, opened it and it looks pretty decent.. board is clean, soldering is precise and clean too ... definitely not manufacture.. machine assembled this piece together. Tried it with ScanMasterELM and works like a charm... same with ScanXL and TeraTerm... ATMA without filters of course produces BUFFER FULL but that's exactly one of the reasons why I am looking for something else to buy.

  6. #6
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    Any interesting device on horizon?
    I was searching the web but it seems there's a huge gap in the market.

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