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CAN BUS Communication

Discussion in 'General Electronics Discussion' started by viktor2113, Nov 4, 2013.

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  1. viktor2113

    viktor2113

    6
    0
    Oct 29, 2013
    Hi,

    I am with the design of a board with CAN communication and I have many doubts about the connection of each module.
    As far as I understood, CAN communication needs only one port to communicate (so one connector with CAN-H,CAN-L and GND). I don't get the physical idea how I'm gonna connect more than 2 modules if I only have one connector.
    Shall I "create" a CAN bus where connect all the modules?
    I saw a few boards with more than one port but I'm pretty sure it can also work with one connector.
    I'm thinking on working with RS-485 and LIN as well, is it the same? Just one connector (RS-485 half with A,B and GND, and LIN with LIN_BUS and GND)

    Thanks
     
  2. GreenGiant

    GreenGiant

    841
    6
    Feb 9, 2012
    CAN works in 2 general layouts, STAR (more complicated to use) and LOOP,

    STAR is you have on central port that is connected to the origin of the signals and then each device is attached to that spot, this is very difficult to use, since there are a lot of things to consider.

    LOOP is one chain of CAN devices, you have the origin, device one, device two, etc. The only stipulation with this is you need terminators (120 ohm resistors) at each end of the line.
     
  3. viktor2113

    viktor2113

    6
    0
    Oct 29, 2013
    I would be interested in a Loop communication. Then I would need at least two ports to connect all the slaves in a kind of chain? Or as I said, I just need one port and connect all the slaves and the master to a BUS? ( I would control the resistor to define the end of the line with a switch) I think I understand all the technical information about it it's just I don't know hoe to create physically this chain with just one connector.
    Thanks for the answer
     
  4. GreenGiant

    GreenGiant

    841
    6
    Feb 9, 2012
    only one port needed, you have the port with a 120OHM resistor across CAN+ and CAN-, the three wires (preferably a twisted pair for high and low) to the first device, then to the second and so on until the last one where you again put a 120OHM resistor from CAN+ to CAN-
     
  5. viktor2113

    viktor2113

    6
    0
    Oct 29, 2013
    Here is what I don't understand. If I have only one connector, I use this connector to communicate CAN1 and CAN2. How can I connect CAN3 to the others if they have the only connector that they have, is already occupied.
    And the same for more slaves of course...
     
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