• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 32 subscribers
  • Views 978 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Port identification on TUSB2046B 4-port hub?

Mark Forbes
Prodigy 110 points
Other Parts Discussed in Thread: TUSB2046B

I'm designing a board that will have three embedded USB serial ports (FT232RL) connected to a single TUSB2046B hub. These ports are connected to three microcontrollers on the board, each of which has a dedicated function. From the upstream PC's perspective, they look like three COM ports. 

When the TUSB2046B is connected, is there some means of determining which port is which? Unlike the usual plug-and-play implementation, I already know which functions are present and I want to assign them to the same COM ports each time. Does the hub initialize with its four downstream ports in the same order every time? Is there some identifier available at the OS level to differentiate between them? The upstream PC is running Windows 10 pro.

I'm a hardware guy, not a Windows programmer, so maybe this is obvious. My objective is to make sure that a given function shows up in the same spot, every single time over the production run. How do I achieve this goal?

  • 0
    TI__Mastermind 18655 points

    That sequence is controlled by the USB host (by the driver), the hub can do nothing to decide which downstream port to enumerate first.

    Just for your information, I've seen that the USB Host usually follow an ascendant order, i.e. Port1, Port2,... but this is not a rule of thumb.

    More than that, I've seen the above sequence when applying power to the port but, after that the enumeration process will be different for each downstream device depending on its Functions, so even if the Port1 is powered up first, the device on Port3 might be finish the enumeration process first.

    Below is a capture showing how the USB host follows a sequence to apply power to each port.

    Regards.

  • 0 in reply to Joel Jimenez0
    Prodigy 110 points

    Thanks! I chose to wire each of my USB-to-Serial converters with DCD and DSR strapped in hardware, so I can identify which port is which regardless of how they appear in Windows. I appreciate the detailed info.

    MGF