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Original question:

TM4C1233H6PGE: Explanation for USBD_STATUS_STALL_PID on the IN pipe needed

TM4C1233H6PZ: How to connect with USB interface if part lacks USB_VBUS signal

Josh%20Mandich
Intellectual 1155 points
Part Number: TM4C1233H6PZ

 

  1. What hardware should I be using to interface the microcontroller to the VBUS pin on the USB connector?
  2. What has to happen to the USB software driver to accommodate this?

The other microcontrollers in this family have a dedicated USB0VBUS pin, but this one seems that it does not (only 2 USB signals).

 I understand this signal is used as an input and an output when the USB enumerates.  

  • 0
    TI__Guru*** 128195 points
    Hello Josh,

    I addressed this question last week here: e2e.ti.com/.../2951677

    There is no VBUS connection, and if they need a VBUS connection, they must use another MCU that has one.

    The TM4C1233H6PZ works only as a USB device, this is stated on the product folder: "Universal Serial Bus (USB) controller with USB 2.0 full-speed (12 Mbps) and low-speed (1.5 Mbps) operation, 32 endpoints, and USB Device mode" which is why there is no VBUS signal.
  • 0
    Prodigy 20 points

    I understand this processor can only be used in device (peripheral) mode.  The USB spec describes 1.5K ohm resistor pullups that may be on DP or DM depending on if the device is low speed or full speed.  I assume these pullups are integrated in the processor.  What I have seen before is that these pullups don't go to VCC, but to the VBUS pin so that the processor can apply (or not apply) VCC to them.  If there is no VBUS pin, are they just connected to unswitched VCC inside the TM4C1233?

  • 0 in reply to Dan Workman
    TI__Guru*** 128195 points

    Hello Dan,

    I am not sure where you are seeing the portion about the pull-ups not going to VCC. USB spec states the pull-up for D+ and D- needs to be a 3.3V. Therefore, it would not use VBUS which is 5V.

    Yes the pull-ups are internal to the device, and they would be connected to VCC which is a 3.3V source as needed. They would not be connected to VBUS regardless because it is a 5V source. This gives the TM4C the flexibility to determine what USB mode is being used before it actually changes any voltages on the bus for the host to see. External resistors would lock the device into a specific speed mode, and thus require hardware changes to adjust the speed (though no one really uses low speed mode).