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    I use these.
    https://www.cobogroup.net/en/product...-01detail.html
    Have 4 of them setup across the vehicle controlling 17 devices. Works well.

    Built in resistor so you can just bridge 2 pins.
    Can have any length branches.
    A lot cheaper than anything else on the market, but we are an OEM.
    If you want a spec sheet let me know.

    Comment


      Originally posted by takai View Post
      Did the 8 pin Tyco ones loop back and forth? The black connector I have here doesn’t seem to adhere to the looping protocol either.

      Or is the looping a white plug thing?
      The white 8 pin cables do indeed loop through the device and back to the hub. Hence why they are 6 wires.

      The black cables are exactly the same, but have an extra wire looped to another pin that engages a termination resistor inside the CAN device.

      Comment


        this is a good interpretation of ISO 11898:1993.

        http://www.ti.com/lit/an/slla270/slla270.pdf

        as with all comms physical layer, you can often get away with an implementation way outside the spec but you should expect to have intermittent problems.

        and if you have intermittent comms problems, halve the bus rate and they'll go away.

        but 500mhz (1mbit) is extremely slow for what is usually a <5m bus length in an automotive application as far as reflection and propagation delay effects are concerned.
        on a very short bus operating at 1mbit a critical length limit is around 40 meters where reflection noise starts to interfere with the signal logic interpretation. to minimise these reflections, bus wire should have characteristic impedance of 120ohm, and should have 120ohm resistors at each end of the longest continuous segment. other than that you can't really fuck it up.

        this is what a long bus without adequate termination looks like. the faster the bus (or the longer the bus run) the larger the % of signalling time this noise takes up.

        Click image for larger version

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        often a long bus makes a good antenna and can pick up high frequency noise (such as AM radio) in certain environments, you can use filtering split terminators (two 60ohm resistors with a cap between them to ground) to reject signal noise above 110% of the bus frequency (ie >550khz). not a problem in a small bus run, inside a metal box (ie a car)

        Oo___oO

        Comment


          Interesting that the quoted TI paper mentions critical length and stub length. That may be interpreted as suitable to have all sub car length stubs and main trunks unterminated.

          The theory is pretty basic physics, so it's interesting to see the physical layer spec being partially implemented, that's all my thoughts were. It may well work just fine in practice.
          Jason Broadhurst

          Someone once asked me if they could use my mower. I said "sure, so long as it doesn't leave my yard"

          Comment


            Talking to the Haltech guys at Motorex, they havent had any issues. Although im guessing the main trunks are much shorter than on an OEM.
            Chris
            ------
            The new nugget
            I never saw a wild thing sorry for itself. A small bird will drop frozen dead from a bough without ever having felt sorry for itself. - D.H.Lawrence

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