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Bytes transmission of CAN protocol (iso 15765)

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  • Bytes transmission of CAN protocol (iso 15765)

    Hi everybody!! I have a doubt wiht some modes in CAN protocol. For example for mode 9, in the SAEJ1979 copy for CAN, the request of infotpe 04 with 0x09 0x04 has a reponse from the ECU with 35 data bytes.
    How is it possible when CAN protocol transmits only 8 data bytes (first data byte is the adittional bytes)?

    I have got some captures of the vehicle, for example: 7E8; 8; 06 41 01 00 06 80 00 AA

  • #2
    The vehicle uses an ISO15765 transport layer on top of CAN to move up to (approx.) 4k logical messages using individual 8 byte frames. This seems like an appropriate question for tech support of whoever sold you the vehicle interface. You're going to need to understand how this works on the vehicle interface you're using.

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    • #3


      This is what a VIN split over multiple CAN frames looks like (ECUsim 5100):

      >0902
      7E8 8 10 14 49 02 01 31 47 31
      7E8 8 21 4A 43 35 34 34 34 52
      7E8 8 22 37 32 35 32 33 36 37

      "10" means it's the first CAN frame, "14" is the number of data bytes. "21" means "consecutive frame, #1", "22" is "consecutive frame #2".

      Vitaliy
      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.

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      • #4
        Originally posted by Vitaliy View Post


        This is what a VIN split over multiple CAN frames looks like (ECUsim 5100):

        >0902
        7E8 8 10 14 49 02 01 31 47 31
        7E8 8 21 4A 43 35 34 34 34 52
        7E8 8 22 37 32 35 32 33 36 37

        "10" means it's the first CAN frame, "14" is the number of data bytes. "21" means "consecutive frame, #1", "22" is "consecutive frame #2".

        Vitaliy
        I wrote a help article on ISO 15765 on my blog (http://www.canbushack.com/blog/index...-it-can-be-fun)

        This may be a good place to start.
        Hack your car's CAN BUS at www.canbushack.com

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        • #5
          Thanks everybody for the information!!

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          • #6
            Hello chewwtoy. Do you know the differences between ISO15765-2 and ISO15765-4?

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            • #7
              Iso15765 part 2 and 4 are completely different documents. Both are part of the Iso15765 standard.
              Part 2 is titled Network layer service
              part 4 is titled Requirements for emissions-related systems

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              • #8
                ISO15765 help

                Does anyone know how I can request the shifter position (Park, Reverse, Neutral, Drive, Manual) using ISO15765?

                Tx

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                • #9
                  Originally posted by kyouabian View Post
                  Does anyone know how I can request the shifter position (Park, Reverse, Neutral, Drive, Manual) using ISO15765?

                  Tx
                  You can't request it.

                  You can monitor the bus, and try to identify which message encodes the shifter position. Given the right tools, it's not hard.

                  Vitaliy
                  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.

                  Comment


                  • #10
                    Originally posted by Vitaliy View Post


                    This is what a VIN split over multiple CAN frames looks like (ECUsim 5100):

                    >0902
                    7E8 8 10 14 49 02 01 31 47 31
                    7E8 8 21 4A 43 35 34 34 34 52
                    7E8 8 22 37 32 35 32 33 36 37

                    "10" means it's the first CAN frame, "14" is the number of data bytes. "21" means "consecutive frame, #1", "22" is "consecutive frame #2".

                    Vitaliy
                    Just a note,

                    the number of data bytes is 014 (12 bits).

                    49 is MODE + 0x40, 02 is the requested PID and 01 is the number of elements transmitted (one VIN).
                    Last edited by reinoso; 11-05-2012, 06:54 AM.

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