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Linux/AM3352: USB OTG setting

Kanae
Guru 10195 points

Part Number: AM3352

Tool/software: Linux

Hi Sitara support Team,

I would like to know the following items of USB_OTG function.

Q1. When I use USB0 on AM335x as RNDIS; USB_Gudget driver base,
 do I have to set USB0 to OTG function by USB0_ID?
 Or the USB0_ID can be left unconnected as following wiki site.
 processors.wiki.ti.com/.../AM335x_Schematic_Checklist

Q2. When I would like to use USB0 as OTG function, I have to set dr_mode = "otg" in the dts file?
 Is my understanding correct?

Best regards,
Kanae

  • 0
    TI__Guru**** 393215 points
    The USB experts have been notified. They will respond here.
  • 0
    TI__Guru**** 175151 points

    Kanae said:
    Q1. When I use USB0 on AM335x as RNDIS; USB_Gudget driver base,
     do I have to set USB0 to OTG function by USB0_ID?
     Or the USB0_ID can be left unconnected as following wiki site.

    If you use USB0 only as RNDIS gadget, never use it as a usb host, you don't need to set it to OTG mode, just leave USB0_ID pin unconnected.

    Kanae said:
    Q2. When I would like to use USB0 as OTG function, I have to set dr_mode = "otg" in the dts file?
     Is my understanding correct?

    Correct. But I just want to clarify that by "OTG" it means DUAL-ROLE. The OTG protocols (such as SRP, HNP) are not supported.

  • 0 in reply to Bin Liu
    Guru 10195 points

    Hi Biser and Bin,


    Thank you for your quick reply.
    I appreciate the notes of OTG.
    I understand that AM335x USB driver does not support OTG function completely.
    Is this limitation caused by the AM335x MUSB's H/W, or only the USB driver of linux SDK?


    Best regards,
    Kanae

  • 0 in reply to Kanae
    TI__Guru**** 175151 points
    The MUSB H/W is capable to support OTG protocol, but Linux SDK doesn't validate those functions because there is no one using it, so OTG protocol is not supported.
  • 0 in reply to Bin Liu
    Guru 10195 points

    Hi Bin,

    Thank you for your reply.
    I understand that the MUSB H/W can support OTG protocol.

    Best regards,
    Kanae