• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 14 subscribers
  • Views 149 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISO1042: connection issue

Giorgio Valente
Prodigy 130 points
Part Number: ISO1042
Other Parts Discussed in Thread: SN65HVD230, ISO7721, SN65HVD23

Tool/software:

Dear support,

i am quite confused about the topic and i ask for your support.

My schematic is stil DRAFT and i attach it here below:

On my board there is a microcontroller and i have two connectors for iso_CAN adn ESC_CAN: the first comes from a device which is referred to isoGND, the second one comes from a device referred to PGND and i need to isolate it from isoGND with ISO1042 device. Microcontroller need to communicate with both devices. 

I am wondering if TXD and RXD can be shorted together as i did: can this cause any issue?

In addition, do i need to consider ESC_CAN as a different CAN bus from iso_CAN? 

Thank you in advance.

BR,

Giorgio

  • 0
    TI__Mastermind 22975 points

    Hello Giorgio, 

    ISO1042's TXD can be connected to SN65HVD230's R pin and the RXD connected to the D pin. This configuration would allow for a message to be passed from ISO_CAN to ESD_CAN and it shouldn't cause any issues. 

    From the information provided, I believe you should consider ESD_CAN and isoCAN separately. If they were connected in any way the ISO1042 would no longer be isolated.

    If you have further questions, a block diagram would be helpful to understand what the goal of your application. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 130 points

    Hello Andrew,

    i think i wasn't clear, so i will attach the following block diagram as you suggested. 

    As you can see isoCAN bus and ESCCAN bus are not the same bus, because iso CAN bus share communication with all those boards referred to isoGND, while ESCCAN bus comes from ESC which is referred to PGND. My goal is to connect ESC CAN bus to ISO CAN bus through ISO1042 in some way: i need that microcontroller (for example) can receive and send messages to ESC. How can i achive this?

    I hope that i was able to describe the problem.

    BR

    Giorgio

    CAN_blockscheme.pdf

  • 0 in reply to Giorgio Valente
    TI__Mastermind 22975 points

    Hello Giorgio, 

    Thank you for the clarification and diagram. I understand that you are trying to connect ESC CAN bus to ISO CAN bus. As you have mentioned, avoid the two CAN busses should not be connected together since they are on separate ground plans. 

    The most robust way to transfer a message from ESC CAN to ISO CAN would be to 

    Unfortunately, there is no simple "CAN buffer" that will isolate just the CAN signal. The two options to do this would be to isolate a CAN bus would be:

    1. Have a microcontroller decode the CAN message from ISO1042 on ESC CAN and re-transmit the message using another ISO1042 or SN65HVD230 to send the message on ISO CAN.
    2. Connect the logic sides of two transceivers together with no microcontroller as descrived above
      1. Andrew J said:
        ISO1042's TXD can be connected to SN65HVD230's R pin and the RXD connected to the D pin. This configuration would allow for a message to be passed from ISO_CAN to ESD_CAN and it shouldn't cause any issues. 

      Best,
      Andrew 

  • 0 in reply to Andrew J
    Prodigy 130 points

    Hi Andrew,

    i attach another block diagram about another possible solution (i am not sure it makes sense).

    By the way, i can't add or change type of microcontroller in order to achieve my goal and microcontroller must be a CAN node. 

    In the new block diagram, i thought i could use a digital isolator with two additional transceiver (i understood that digital isolator cannot handle directly with CAN signals) and then connect together the two buses on ISO CAN.

    Let me know what you think about it.

    BR

    Giorgio 

    0804.iso_CAN.pdf

  • +1 in reply to Giorgio Valente
    TI__Mastermind 22975 points

    Hello Giorgio,

    The following block diagram makes sense and should work. Please keep in mind that you could also use ISO1042 to integrate the ISO7721 and one of the SN65HVD23.

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 130 points

    Hi Andrew,

    thank you for the support, i will try this last solution.

    BR

    Giorgio