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USB Host mode

Mark Pieper
Expert 4640 points
Other Parts Discussed in Thread: TPS65950

I received this inquiry from one of my customers and our local OMAP support guys are on vacation. Can anyone help? (below edited to remove some customer info)

"I am seeing a problem with the USB OTG port. The OTG port is driven from the TPS65950. I have the lines for this port connected directly to the connector on the baseboard. We are attempting to use this port in a host only configuration. I have the DP and DM lines connected directly to the USB connector on the baseboard. I have the ID line connected to a 10K resistor to ground and I don’t have VBUS connected. I am using a separate on-board 5V supply.

The problem I am seeing looks like the TPS65950 is driving the USB line low (at least the DP line). Under normal circumstances, when a USB function device is plugged in, it should pull-up the DP or the DM line to indicate that it has connected. In the design I am debugging this doesn’t happen. The DP line stays low. I attempted to add a 1K pull-up resistor to this line to verify and it still couldn’t be pulled high. However, if I halt the boot before the GreenHills SW driver is implemented, the DP line pulls high. I suspect something in our setup is configuring the TPS65950 incorrectly. Can you provide me any insight into what may be happening? Is there a recommended configuration for using this port in a Host only mode? Register setup? HW configuration? Anything you can provide would be helpful."

  • 0
    TI__Genius 15100 points

    Hi Mark,

    If you want to check/configure the DP status on the TPS65950 then you can check register OTG_CTRL. I am not very sure about the handshake/protocol on USB. I hope the register setting may be helpful.

    Let me know if I can be of more help.

    Regards,

    Gandhar.

     

  • 0
    Prodigy 155 points

    Hello Mark,

    I was wondering how you handled your situation.

    I am too trying to use HOST only mode, with an external supply. Can this all be done by register setting? VBUS can be controlled by the OTG_CTRL register, but what about permanent HOST? Can it be configured permanently by register? Should ID pin be wired high or low in the design for this to happen?

    Thanks,

    Matan

  • 0 in reply to Matan Medalion
    TI__Genius 15100 points

    Hi Matan,

    Mark can provide his inputs.

    Here is what I can provice - For HOST mode with external supply, make sure you do not start the internal charge pump. Also, it is recommeded that you connect the device VBUS pad to the USB connector. For HOST mode the ID is connected to GND.

    Hope this helps.

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    Prodigy 155 points

    Hi Gandhar,

    Thanks for your answer. I need a clarification regarding your following sentence:

    "Also, it is recommeded that you connect the device VBUS pad to the USB connector".

    As I've mentioned, my Host USB connector accepts its VBUS power supply externally and constantly (whether a device is connected or not). So, VBUS pin on the connector is already connected - How can I comply with your recommendation above and connect it also to the TPS65920 VBUS pad?

    Thanks,

    Matan

  • 0 in reply to Matan Medalion
    TI__Genius 15100 points

    YOu are supplying 5V from an external supply. The device will not recognise this supply. This is incase you want the device to detect the supply.

    Generally, the VBUS interrut is used on the system and hence the suggestion.

     

    Regards,

    Gandhar.