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CAN transceiver SN65HVD26x

Smitesh Modak
Prodigy 170 points

Other Parts Discussed in Thread: TMS320F28335

I have all the 3 IC's of SN65HVD26x series. I have connected the 265 IC for testing purpose. I have given a DC input to the 265 IC. When I connect Tx terminal to logic 1(5V) i obtain the recessive mode (CANH=2.45V and CANL=2.45V) as desired. However when I connect logic 0 (0V) the output of the IC is still in recessive mode i.e. CANH=2.45V and CANL=2.45V. I have also connected the pin 8 i.e. select pin to ground. I have terminated the bus using 120ohm resistor. I'm getting constant 5V at the Rx terminal. Is there any more specific connection needed.

I'm not able to understand why am I getting 4.5V at CANH and CANL when I give 0V at the Tx. The IC is constantly working in recessive mode.

  • 0
    TI__Guru 62920 points
    Hi Smitesh,

    These devices have a "dominant time-out" feature that forces the CAN outputs to be recessive after they have been dominant for a period greater than 1175 us (minimum). This is to prevent something like a malfunctioning CAN controller from holding a bus dominant indefinitely and preventing further communication. If you provide a constant low-level on TXD, though, you will likely only be able to observe a recessive output. Instead, you will need to toggle the TXD pin frequently enough that the time-out is not triggered.

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Prodigy 170 points

    Thank You so much Max. It was really helpful.

    I have a battery whose output is CAN H and CAN L. I am connecting the output of battery to tranceiver IC and TX and RX of the IC to DSP processor TMS320f28335.

    Now i want to read the output of the battery, can u suggest me of the code that can be used to monitor the data and use it for further task. I could communicate via CAN transceiver between two DSP boards(i.e. in Self Test Mode)  but i am not aware where does the data gets store, i.e. in which mailbox, when operating in NORMAL MODE and what is the code for it and any more hardware changes.

    Thank You.

  • 0 in reply to Smitesh Modak
    TI__Guru 62920 points
    Smitesh,

    I'm happy to help! For your last question, though, it would probably be better to check with our microcontroller team. They should be able to give you some guidance on how to implement CAN communication using TMS320f28335. Their support forum can be found here: e2e.ti.com/.../171.

    Best regards,
    Max