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SN65HVDA100-Q1: LIN Bus communication Error

Ritesh Patel
Intellectual 560 points
Part Number: SN65HVDA100-Q1

Hi,

We are using SN65HVDA100QDRQ1 LIN PHY on our custom board and able to send data from Master LIN (Populated D22 & R363 in below Image) to Slave LIN. 

However, we are able to receive the data sent by Master but few character from the received string will change. For Ex. When I sent "xyz" then I received "yz" on the Slave device. When I sent "55" then I received "5'" (Only 5) on the Slave side. We are using 1-Feet cable only between Master & Slave board.

I have attached LIN schematic for your review. 

Kindly review the same & let me know if any change required.

Thanks,

Ritesh

  • 0
    TI__Guru 70762 points
    Ritesh,

    Does the slave device have the same schematic, just with D22 and R363 not populated? The one thing that could be causing this is too much capacitance on the bus or on the RX pin of the slave device.

    Can you share a schematic of the slave device? And is there any way the LIN bus can be probed while communication is happening?

    Regards,
  • 0 in reply to Eric Hackett
    Intellectual 560 points

    Thank you Eric for earliest response.

    Yes, I am using our another custom board as a slave device.

    We have connected two boards via 24AWG wire.

    Is this something due to current limitation on INH pin? I have connected INH pin to series diode & resistor for Master configuration.

  • 0 in reply to Ritesh Patel
    Intellectual 560 points

    Hi Eric,

    See attached image of the LIN BUS. We are sending "55" on the bus.

    The voltage levels seem improper during communication.

    Early responses would be greatly appreciated.

    Thanks,

    Ritesh

  • 0 in reply to Ritesh Patel
    TI__Guru 70762 points

    Ritesh,

    I'm a little confused by the oscilloscope shot, is each transition supposed to be happening on that screenshot? It looks like edges aren't transitioning quickly enough for the upper and lower voltages to be met. I have a couple of questions:

    • What is the length of the cable being used to connect the boards?
    • What message rate is being used?
    • Can the Q33 FET be removed and then the bus communication tested again? I'm curious if the transistor is causing too much capacitance or current draw on the bus.

    Regards,

  • 0 in reply to Eric Hackett
    TI__Guru 62920 points
    Hi Ritesh,

    Were you able to resolve your issue? Like Eric mentioned, it looks to me like the edge transitions are not quick enough for the data rate you are trying to use. SN65HVDA100-Q1 and most other LIN transceivers have slew rate limiting on their outputs in order to mitigate EMI, and this limits the operation to about 20 kbps.

    Max