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TMS320C5517 USB bubble error

Jean-Christophe Billard
Intellectual 730 points
Other Parts Discussed in Thread: TMS320C5517

Hi all,

so we are basically facing an issue on a custom board and would love to get your thoughts on this. 

C5517 is connected to host through USB 2.0 mini and is used to transfer data at high rate ~500ko/s. 

The issue we are facing is random but regular USB bubble error from all tested hosts (Linux, Windows and Mac). We highly suspect a ground issue, knowing USB is on flex conductor and that the error is persistent even at lower data rate (so DSP burden does not seem to be the issue).

Has anyone experienced similar issue and could provide help on that front. Also we want to draw the eye diagram with our board, does TI provide a USB test mode script that we could use to quickly run our diagnosis ?

Best regards,

Jean

  • 0
    TI__Genius 12575 points

    Hi Jean,

    Could you Pl answer my questions.

    Have you tried using USB analyzer and verify/analyze the error ? Do you have any further information ?

    Could you let us know the reason that you are suspecting the ground issue. Are you seeing high impedance between USB shield ground and the board ground. Could you ensure you have low impedance between these two. This would avoid any ground noise issue.

    Regards

     Vasanth

  • 0 in reply to Vasantha K
    Intellectual 730 points
    Hi Vasanth,

    thank you for your input. Ground impedance is fine at DC, but I was more concerned of issues at high frequencies (dynamique impedance).
    Anyhow, we got the firmware setup on a different and verified hardware and we found that as we are transmitting bulk data at high rate, we might be limited by processing and we are currently upgrading to DMA.

    During my search I found this link from for USB testing (to whome it may be of interest).

    Validating High- and Full-Speed USB on TMS320C5517
    www.ti.com/.../sprabu3.pdf

    Best,

    JC