Windows 10 Usb type-c Alternate mode RRS feed

  • Question

  • I have a Windows 10 machine with USB Type-C port. As known USB Type-C connector supports Alternate mode (DisplayPort/MHL) functionality, this USB Type-C port is connected 
    to a test board which receives the frames from the windows 10 machine and does certain processing (CRC check etc.. ). This test board is connected to a display.

    As per my understanding, 
    1. Microsoft provides USB Type-C connector client driver, UcmUcsi.sys, that implement the features defined in the UCSI specification, if not develop a custom client driver for USB Type-c.
    1. To get the Alternate mode functionality supported by USB Type-C, we have the USB Type-C connector client driver in which it states that USB Type-C client driver will
    Advertise and negotiate alternate modes, and configure the Mux if an alternate mode is detected. The client driver is responsible for deciding the alternate mode to negotiate.

    Am Assuming that when the display device is connected to USB Type-C port, negotiate the alternate mode and enter the mode (DisplayPort/MHL),this will be be supported by the default Microsoft provided USB Type-c connector client driver as per the UCSI spec.

    Is this assumption correct?

    Next in my case, am connecting the test board to the USB Type-C port on windows 10 machine, do i need to write a custom USB Type-C connector client driver or i need to write a firmware for the test board to get the alternate mode functionality?

    Please provide your valuable input.


    Monday, April 4, 2016 11:54 AM


  • Hi Shwetha,

    If you know your system supports UCSI and the Microsoft ucmucsi.sys driver is loaded, you are correct that the alternate mode negotiation is handled in firmware. If you aren't sure if your system supports UCSI and the driver is not loaded, then it probably does not support UCSI.

    You also need to make sure the test system supports the DisplayPort alternate mode. You do not need to write a custom driver; if the system supports the alternate mode, the drivers it came with will handle the alternate mode negotiation.

    After you've guaranteed that the test system supports the alternate mode, you need to write the firmware for your board such that it correctly advertises and negotiates the alternate mode.

    Once you've updated your board's firmware to properly handle the alternate mode, you should be able to connect it to your test system and they will be able to negotiate and enter the alternate mode.


    Monday, April 11, 2016 4:45 PM