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withSN65LVPE502B, it can't be identified USB2.0

Shinichi Inoue
Guru 20351 points
Other Parts Discussed in Thread: SN65LVPE502A, SN65LVPE512

Dear Specialists,

MY customer is evaluating with SN65LVPE502B, EZ-USB FX3(cypress) and PC.

Depend on the connect sequence of 3 devices, USB2.0 connection is not recognized.

The phenomenon is occurred not only SN65LVPE502B, but also SN65LVPE502A and SN65LVPE512.

Could you please advise the reason and the solution?

TEST Condition 
 EZ USB -> USB3.0 Cable ->  SN65LVPE502BEVM -> USB2.0 Cable -> PC

Power supply of 502B is self powered 3.3V. (Vbus is not using) 

EN is ON at the same time. 

(1)Connection Sequence 1　 USB2.0 recognition is NG 

 1.  connect EZ USB and SN65LVPE502BEVM

 2.  connect SN65LVPE502BEVM and PC

This is similar to Device side connection.

(2)Connection Sequence2 USB2.0 recognition is OK

 1.  connect SN65LVPE502BEVM and PC

 2.  connect EZ USB and SN65LVPE502BEVM

This is similar to Host connection.

When these devices use device side, it may require a little ingeuity

I appreciate your great help.

Best regards,

Shinichi

  • 0
    TI__Mastermind 36085 points
    Hello,

    I would like to review an USB trace of the issue, seems that the USB device is trying to connect to SS due to RX detection, however this shouldn't happen since the re-driver has no far end RX termination on the Host side.

    Regards,
    Diego.
  • 0
    TI__Mastermind 36085 points

    Hello,

        Do you have a USB trace of the issue?. Are you able to reproduce the issue with more cables?

    Regards,

    Diego.

  • 0 in reply to Diego Cortes
    Guru 20351 points

    Dear Diego

    Thank you for your reply.

    I sent your message to the customer.

    In this case, he is using EVM and USB cable.

    I ask him to change the cable and check the result.

    Could you please wait a few days.

    I appreciate your great help.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    Guru 20351 points

    Dear Diego

    I'm sorry for late reply.

    The customer was confirming about your request.

    By changing the cable, it was a same result, it can't beidentified USB2.0.

    When the customer was confirmed 502B's Device Rx,  it seems to be established  Rx termination.

    Could you please see attached file.

    I can understand Tx termination is established.

    But I can't understand why Rx termination is established.

    This may lead to EZ USB false recognition.  

    Could you please advise?  

    Best regards,

    Shinichi

    connection between Host, Redriver and Device driver.pptx

  • 0 in reply to Shinichi Inoue
    TI__Expert 8000 points

    Can you confirm if the 502B actually has termination enabled?  you can do this by placing an ohm meter between 502B VCC and 502B Device (Or Host) RX pin, if termination is disabled, you should read ~80K Ohms, if termination is enabled you should read less than 50 ohms.

    It appears the EZ HUB may be checking for the presence of a SS device differentially, which could result in the false detection. 

  • 0 in reply to Undrea Fields
    Guru 20351 points

    Dear Undrea

    Thank you for your reply.

    I confirmed the customer.

     Between EZ-USB and repeater is connected USB3.0 cable,

    EZ-USB Tx and repeater Rx, although the impedance is 83kohm,  EZ-USB changed SuperSpeed.

    Repeater Tx and  EZ-USB Rx is still Rx Detected. 

    Could you please see attached file and advise.

    In addition, this situation is the same as SN65LVPE512.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi

    impedance of SN65LVPE502.pptx

  • 0 in reply to Shinichi Inoue
    TI__Expert 8000 points

    It appears the EZ-USB device does not follow the USB spec Rx Detect implementation.  During Rx.Detect the circuitry should detect whether a load impedance is present based on the principle of the RC time constant of the circuit. The LVPE502A/B and LVPE512 will measure ~100 ohm impedance between Rx+ and Rx-, but this impedance is not the load impedance that is present when terminations are enabled.  The EZ-USB device appears to detect the presence of a device by detecting the low impedance between the Rx+ and - pins which in the case of the LVPE502A/B will always be present.

  • 0 in reply to Undrea Fields
    Guru 20351 points
    Dear Undrea

    Thank you for your reply.

    I understand EZ-USB doesn't follow the USB spec.

    I'll feedback this information to the customer.

    Could I confirm, you mentioned before measure point of the impedance is between 502B VCC and 502B Device Rx pin.
    Why is not measured 502B VCC and 502B Device GND pin.

    I appreciate your great help and cooperation.

    Best regards,
    Shinichi