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Thread: ATD1 non-CAN

  1. #1
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    ATD1 non-CAN

    So, I'm playing with ATD1 just to see what happens. From the datasheet:

    Standard CAN (ISO 15765-4) OBD requires that all messages have 8 data bytes, so displaying the number of data bytes (the DLC) is not normally very useful. When experimenting with other protocols, however, it may be useful to be able to see what the data lengths are. The D0 and D1 commands control the display of the DLC digit (the headers must also be on in order to see this digit). When displayed, the single DLC digit will appear between the ID (header) bytes and the data bytes. The default setting is determined by PP 29.
    My reading of this is that protocols other than CAN should be doing something when I set ATD1, but I'm not seeing that. I'm using an [awesome] ECUsim 2000 with an OBDLink.

    J1850 PWM:
    Code:
    >ATH1
    OK
    >ATD0
    OK
    >ATDP
    AUTO, SAE J1850 PWM
    >0100
    41 6B 10 41 00 BE 1B 30 13 80 
    41 6B 18 41 00 88 18 00 10 3E 
    41 6B 28 41 00 00 08 00 10 59 
    >ATD1
    OK
    >0100
    41 6B 10 41 00 BE 1B 30 13 80 
    41 6B 18 41 00 88 18 00 10 3E 
    41 6B 28 41 00 00 08 00 10 59 
    >
    J1850 VPW:
    Code:
    >ATH1
    OK
    >ATD0
    OK
    >0100
    SEARCHING...
    48 6B 10 41 00 BE 1B 30 13 EA
    48 6B 18 41 00 88 18 00 10 54
    48 6B 28 41 00 00 08 00 10 33
    >ATDP
    AUTO, SAE J1850 VPW
    >ATD1
    OK
    >0100
    48 6B 10 41 00 BE 1B 30 13 EA
    48 6B 18 41 00 88 18 00 10 54
    48 6B 28 41 00 00 08 00 10 33
    >
    9141-2:
    Code:
    >ATD0
    OK
    >0100
    SEARCHING...
    48 6B 10 41 00 BE 1B 30 13 20 
    48 6B 18 41 00 88 18 00 10 BC 
    48 6B 28 41 00 00 08 00 10 34 
    >ATD1
    OK
    >0100
    48 6B 10 41 00 BE 1B 30 13 20 
    48 6B 18 41 00 88 18 00 10 BC 
    48 6B 28 41 00 00 08 00 10 34 
    >ATDP
    AUTO, ISO 9141-2
    >
    KWP Fast:
    Code:
    >ATD0
    OK
    >0100
    86 F1 10 41 00 BE 1B 30 13 E4 
    86 F1 18 41 00 88 18 00 10 80 
    86 F1 28 41 00 00 08 00 10 F8 
    >ATD1
    OK
    >0100
    86 F1 10 41 00 BE 1B 30 13 E4 
    86 F1 18 41 00 88 18 00 10 80 
    86 F1 28 41 00 00 08 00 10 F8 
    >ATDP
    AUTO, ISO 14230-4 (KWP FAST)
    >
    And, of course, CAN:
    Code:
    >0100
    SEARCHING...
    18 DA F1 10 06 41 00 BE 1B 30 13 00 
    18 DA F1 18 06 41 00 88 18 00 10 00 
    18 DA F1 28 06 41 00 00 08 00 10 00 
    >atd1
    OK
    >0100
    18 DA F1 10 8 06 41 00 BE 1B 30 13 00 
    18 DA F1 18 8 06 41 00 88 18 00 10 00 
    18 DA F1 28 8 06 41 00 00 08 00 10 00 
    >atdp
    AUTO, ISO 15765-4 (CAN 29/500)
    >
    So, experimentally, it only appears to work for CAN. Which is boring as hell, because as the datasheet says, for CAN the number will always be eight.

    Gary (-;
    OBDGPSLogger, for logging OBDII and/or GPS data
    OBDSim, an OBDII/ELM327 software simulator
    mp3car forums: obdgpslogger, obdsim

  2. #2
    Newbie preet's Avatar
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    Hey,

    I think this may be for the "custom CAN" protocols you can try with the ELM, and not ISO-15765-4. ISO 15765-TP or some other standard maybe? The other (J1850, etc) standards don't necessarily incorporate DLC in their message frames.

  3. #3
    SuperMod - OBDII GPS Logger forum
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    Hrm. Well, that fits with what I observe, although it doesn't feel intuitively satisfactory.

    One way or the other, obdsim supports ATD1 for CAN protocols, and not others. Should work for you, by my reading of the thread you started on the obdsim forum.

    Gary (-;
    OBDGPSLogger, for logging OBDII and/or GPS data
    OBDSim, an OBDII/ELM327 software simulator
    mp3car forums: obdgpslogger, obdsim

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