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USB Not Detected after SYS_nRESPWRON is given

Suresh Samynathan
Intellectual 360 points
Other Parts Discussed in Thread: OMAP3503, TPS65950

Hi,

In our application OMAP3503 and TPS65950 is used with TPS USB PHY used as device interface. A manual reset switch is connected to SYS_nRESPWRON.

When the reset is applied with USB connected to TPS65950, the OMAP gets reset and boots up. After booting the USB interface is not getting detected by the host PC. If the USB cable is removed and connected again, then the USB is getting detected.

When the reset is applied with the USB disconnected condition of TPS65950, after booting the USB interface is detected if the USB is connected.

The same issue is observed in the ZOOM SOM module. Can you please clarify what could be the problem.

  • 0
    TI__Genius 15100 points

    nRESPWRON reset will reset the OMAP device but will not reset the TPS65950.

    For detecting the USB cable the VBUS has a threshold and it is edge sensitive. So, when you connect a USB cable after reset the system detects an edge. If the cable is already connected then there is no edge in this case.

    Hope this clarifies.

     

    Regards,

    Gandhar.

     

     

  • 0 in reply to Gandhar Dighe
    Intellectual 360 points

    Hi Gandhar,

    Sorry, the issue is USB not getting detected even after removing and plugging in the USB cable if the reset is applied with USB plugged in condition.

  • 0 in reply to Suresh Samynathan
    Intellectual 360 points

    Hi,

    Any update on the above issue.

  • 0 in reply to Suresh Samynathan
    TI__Genius 15100 points

    Applying a SYS-nRESPWRON only to OMAP will reset OMAP. I guess USB block on OMAP will also reset. I am not sure if such a reset will continue proper handshake on the USB interface. You are resetting the OMAP USB module, however, the TPS65950 is still connected. I think that such a one sided reset is causing any issues.

    Such a reset may be an asynchronous reset and the interface may need proper reset for correct communication.

    Is it possible to see the status of the STP, NXT and DIR when the problem occurs, how is it different from normal operation. Can you read the FUNC_CTRL[5] bit in TPS65950 when the detection is not done. I hope when OMAP reboots you can still access TPS65950 registers and can check this bit.

    Let me know the above observations and we can debug further.

     

    Regards,

    Gandhar.