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Hot!Multi-node eCan errors

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RobDwi
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2020/08/08 00:36:23 (permalink)
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Multi-node eCan errors

Hi I am brand new to this forum.
I have an mplab x ide project with multiple pic18f25k80 chips set up on one pc board with a common can bus, the circuit also includes an LCD screen displaying information from each node, if I connect two of the nodes to the can bus all works well, if I connect another node the bus goes into error mode. I have tried all sorts of settings. I am using the XC8 free version and am wondering if their is a limitation on the compilation side of having more than two pics running eCAN modules ?
1 X LCD screen 18F25K80 chip receives only can standard msg through 2 wire bus.
4 x nodes used analytically 18F25K80 chips send standard msg only to can bus.
can bus is only 100 mm long and has 120ohm terminator.
the electo-oscilloscope images are of the 2 wire can bus. 
The images are of the two stages no error and error   

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    crosland
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    Re: Multi-node eCan errors 2020/08/08 08:43:59 (permalink)
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    Free mode compiler is irrelevant.
     
    You also need a common 0V reference for CAN.
     
    What do the ECAN error status bits tell you?
     
     
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    RobDwi
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    Re: Multi-node eCan errors 2020/08/08 18:53:34 (permalink)
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    Thanks Crosland, the nodes all share the same supply Vdd Vss if that is what you meant by "common 0v reference for can" ? or is vRef- from each pic need to be linked ?, or is that referencing the can ?
    I am using the Ecan module in the 18F25k80 chip, but i'm thinking now I should be using  a bus connect chip ata6564 or similar and use the 18f25k80 as a slave do drive it. Is that what the general synopsis is ?
    I have just read a thread about using breadboards for can projects which i used to test this system, apparently that is a no no, which may be the problem, so I am making a pcb now and including a can chip for each of the pic chips, and the can chips are 5 times faster as well. Instant parallel recognition is what this project is about. I'll post here when assembled again.
    post edited by RobDwi - 2020/08/09 00:20:52

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    crosland
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    Re: Multi-node eCan errors 2020/08/09 08:29:56 (permalink)
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    RobDwi
    Thanks Crosland, the nodes all share the same supply Vdd Vss if that is what you meant by "common 0v reference for can" ? or is vRef- from each pic need to be linked ?, or is that referencing the can ?

    It means exactly what it says. All nodes must share the same 0V connection.
     

    I am using the Ecan module in the 18F25k80 chip, but i'm thinking now I should be using  a bus connect chip ata6564 or similar and use the 18f25k80 as a slave do drive it. Is that what the general synopsis is ?

    No.
     

    I have just read a thread about using breadboards for can projects which i used to test this system, apparently that is a no no, which may be the problem,

    Breadboards are a problem for any application, nothing specific to CAN.
     

    so I am making a pcb now and including a can chip for each of the pic chips, and the can chips are 5 times faster as well.

    The maximum bit rate for CAN is 1Mbit/s which is fully supported by the ECAN. Why add the extra software overhead of interfacing an external chip?
     
    If you want the faster bit rate of CAN FD then why did you even start with the ECAN? CAN and CAN FD devices cannot talk to each other
     
    Instant parallel recognition is what this project is about.

     
    No idea what that means.
     
    #4
    crosland
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    Re: Multi-node eCan errors 2020/08/09 08:34:54 (permalink)
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    So I just looked at the ATA 6564. That's a CAN FD transceiver, not a controller.
     
    Did you even have a CAN transceiver on your original design?
     
    A transceiver is REQUIRED for CAN.
     
    Using a CAN FD transceiver with the ECAN will not give you any speed advantage.
     
    I'll ask again, what did the ECAN status register tell you about the error?
    #5
    RobDwi
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    Re: Multi-node eCan errors 2020/08/09 18:37:16 (permalink)
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    @Crosland Thanks for your input, I don't wish to be condescending but the pic18f25k80 pic chip is as this extraction from the datasheet displays, 
    ECAN Bus Module Features:
    • Conforms to CAN 2.0B Active Specification
    • Three Operating modes:
    - Legacy mode (full backward compatibility with
    existing PIC18CXX8/FXX8 CAN modules)
    - Enhanced mode
    - FIFO mode or programmable TX/RX buffers
    • Message Bit Rates up to 1 Mbps
    • DeviceNet™ Data Byte Filter Support
    • Six Programmable Receive/Transmit Buffers
    • Three Dedicated Transmit Buffers with Prioritization
    • Two Dedicated Receive Buffers
    ECAN Bus Module Features (Continued):
    • 16 Full, 29-Bit Acceptance Filters with Dynamic
    Association
    • Three Full, 29-Bit Acceptance Masks
    • Automatic Remote Frame Handling
    • Advanced Error Management Features


    These notes are all descriptions of an ecan transceiver am I misreading all that somehow, do you think this describes it as not a transceiver.?
    The attached image displays the can errors for your question "What do the ECAN error status bits tell you?"
     
    #6
    ric
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    Re: Multi-node eCan errors 2020/08/09 20:57:32 (permalink)
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    They all sound like features of a CAN controller, not a transceiver, which is exactly what crosland stated.
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #7
    RobDwi
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    Re: Multi-node eCan errors 2020/08/09 23:37:11 (permalink)
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    ric
    thanks for your input
    I was under the opinion that the 18f66K80 family had an inbuilt transceiver, but it is only a controller. it al makes sense now.Smile: Smile
    I sort of asked that earlier in the conversation.
    "I am using the Ecan module in the 18F25k80 chip, but i'm thinking now I should be using  a bus connect chip ata6564 or similar and use the 18f25k80 as a slave do drive it. Is that what the general synopsis is ?"
    #8
    ric
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    Re: Multi-node eCan errors 2020/08/09 23:40:05 (permalink)
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    That question was clearly answered in post#4.
     

    I also post at: PicForum
    Links to useful PIC information: http://picforum.ric323.co...opic.php?f=59&t=15
    NEW USERS: Posting images, links and code - workaround for restrictions.
    To get a useful answer, always state which PIC you are using!
    #9
    RobDwi
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    Re: Multi-node eCan errors 2020/08/10 00:10:27 (permalink)
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    Thanks Ric and crosland
    thanking you again crosland you were right there was no transceivers in the circuit but there will be now. if ya stop learning ya stop living, that finished that brain drain with the errors. I had a circuit with 6 controllers  and no transceivers LOL
    cheers
    #10
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