Installing the Windows libusbK Driver

Efinix provides a custom Windows libusbK driver installer for enabling FTDI communication with Efinix development boards (before March 2026 you had to download software from Zadig). You install drivers for:

  • Interface 1 (JTAG communication)
  • Interface 0 (SPI communication)
Important: For some Efinix development boards, Windows automatically installs drivers for some interfaces when you connect the board to your computer. You do not need to install another driver for these interfaces. Refer to the user guide for your development board for specific driver installation requirements.
Tip: Download the Windows FTDI driver from the Support Center.

To install the driver:

  1. Unzip the driver files into a temporary directory.
  2. Right click efx_libusbk_amd64_i1.inf.
  3. Choose Install option from the pop-up menu.
  4. Click Install when prompted by Windows Security to install the device software.
    • (Optional) Turn on the Always trust software from 'Efinix, Inc.' option.
  5. Click OK when prompted that operation has completed successfully.
  6. (Optional) Enable Interface 0 by repeating steps 1 - 4 with the efx_libusbk_amd64_i0.inf file.

The new driver(s) appear in the Windows Device Manager Universal Serial Bus folder.