• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Subscribers 33 subscribers
  • Views 1073 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

CANBUS protocol

golan kormian
Intellectual 880 points
Other Parts Discussed in Thread: SN65HVD233

hi,

i am using the SN65HVD233 RX/TX  pins connect to microchip PIC24 uart input.

what is the protocol between the PIC and the SN65HVD233?

is it regular UART (like RS232) or we need special software implement of CANBUS protocol at the PIC?

at the CAN EVM (slu158) how do i connec the RXD/TXD at JMP2 to run the board?

  • 0
    TI__Mastermind 20590 points

    Hi Golan,

    A UART will not use the CAN protocol.  CAN protocol is defined in various ISO standards such as ISO11898-1 and then built upon at the applicaiton by SAE and CANopen (CAN in Automation) for example.  I'm not familiar with the PIC MCU and any capabilities or s/w they may have to convert the UART to a CAN protocol.  Normally you would connect the CAN transceiver (PHY, HVD233) to a CAN controller on the MCU  which is a special peripeheral like a UART, SPI or timer. The CAN controller will handle all the low level CAN protocol topics like arbitration (addressing), bit stuffing, CRCs, etc that are needed in the protocol.  The MCU would then have a s/w layer that would handle the application level of the CAN protocol.   Alternatively you could look at a Stellaris MCU or Picolo DSP from TI that has a CAN controller and appropriate s/w for CAN. 

    If you use the UART you are just using the CAN transceivers as a level shifter to CAN signaling for line driving / receiving and not taking advantage of any of the CAN protocol.

    For the CAN EVM you can simply use a pinch connector cable to grab TXD/RXD pins on the EVM or build a simple cable to adapt to your uP target board using the header layout. 

    Regards,

    Scott

  • 0 in reply to Scott Monroe
    Intellectual 880 points

    hi,

    if i want to connect the CAN RX/TX to regular I/O pins at the MCU, do u have any software code that implement CAN protocol?

  • 0 in reply to golan kormian
    TI__Mastermind 20590 points

    TI provides CAN software for TI processors with CAN controllers on board.  Please refer to the TI MCU, DSP and uP pages for that information.   We do not provide CAN s/w for competitors microprocessors. 

    -- Scott

  • 0 in reply to Scott Monroe
    Intellectual 880 points

    hi,

    at the SN65HVD233 what are the voltage levels at pins 1,4 D and R (RX/TX) minimum and maximum levels?

    is the output is regular CAN protocol?

    i intend to use a component MCP2515 which is CAN controller to SPI since at the MCU i use there are no CAN  pins inputs.

    do u think they can work together?

    http://ww1.microchip.com/downloads/en/devicedoc/21801d.pdf

     

  • 0
    Intellectual 880 points

    HI,

    at the SN65HVD233 what are pins D and R (1,4) exactlly?

    ther do not describe at the data sheet.

  • 0 in reply to golan kormian
    TI__Mastermind 20590 points

    D and R pins are described in the datasheet on page 3,  VI, abs max voltage rating.  Page 3 Recommended Operating Conditions:  D pin VIH input threshold high 2V to 5.5V, VIL (input threshold low 0 to 0.8V). and R pin output IOL -10mA max IOH and IOH 10mA max.  Pag 4 has the internal pull up current on D pin IIH and IIL.  Page 6 has R pin VOH and VOL. 

    The CAN transceiver doesn't talk can Protocol:  it level shifts and is the Physical Layer for CAN.  The HVD233 is compatible to the ISO11898-2 CAN physical layer standard. 

    - Scott

  • 0 in reply to Scott Monroe
    Intellectual 880 points

    Scot,

    sorry but i didnt find any of it.

    i asked simple question - what is the functionality of the R and D pins ? it is not at the spec, or i do not understand it if its there.............

    which is the tranceive and which is the recieve?

    please send screen shots of the voltage levels of these pins.

     

    golan

  • 0 in reply to golan kormian
    TI__Mastermind 20590 points

    Please look at page 1, block diagrams so you can see functionally where the D and R are connected.  D = Transmit Data (this is what will be driven to the bus), R = Receive Data which is what the receiver sees on the bus.  This is the core Transmit / Receive functions for the HVD23x CAN transceiver.   Electrical specs for the pins are in the previous answer.

    -- Scott