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Can DM/DP lines of USB is used as UART TX/RX?

Vishal Dhanani
Prodigy 60 points

Hi,

As per datasheet of AM335X, The internal USB PHY can be configured to multiplex the UART2_TX or UART2_RX signals with USB0_DM or USB0_DP terminals.

So, if i want to use USB data pins as UART pins, then what care i should have to taken care?

Is voltage levels of UART TX & RX will be 3.3V?

Best Regards,

Vishal Dhanani

  • 0
    TI__Guru**** 161600 points

    Hi Vishal,

    As I see in AM335x data sheet (zcz &zce package):

     zce ball U18 & zcz ball N18, pin name USB0_DM, has ONLY ONE muxmode: Mux Mode 0, which corresponds to USB0_DM

     zce ball U19 & zcz ball N17, pin name USB0_DP, has ONLY ONE muxmode: Mux Mode 0, which corresponds to USB0_DP

    This means that there is NO possibility to mux USB0_DM & USB0_DP as uart_tx/rx.

    Is voltage levels of UART TX & RX will be 3.3V?

    Yes, they are 3.3V/

    Best Regards,

    Yordan

  • 0 in reply to Yordan Kovachev
    Prodigy 60 points

    Hi Yordan,

     Thanks for your reply.

     But as per comment 13 (marked in column of RESET REL. MODE), The internal USB PHY can be configured to multiplex the UART3_TX or UART3_RX signals to this terminal.

    Best Regards,

    Vishal Dhanani

  • 0 in reply to Vishal Dhanani
    TI__Guru**** 161600 points
    Hi Vishal,

    Sorry, my mistake, I didn't notice the note. Apologies for the confusion.

    To make this work, you have to follow the settings provided in Section 16.1.4 USB GPIO Details & Figure 16-2. USB GPIO Integration of the TRM. The register that needs to be configured is described in 9.3.1.19 usb_ctrl0 Register (offset = 620h) [reset = 0h]

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    TI__Guru 59615 points
    The USB0_DP and USB0_DM operating as UART will be 3.3 volts.

    Regards,
    Paul