The HDMI-Adapters are pre-programmed with the firmware. If you want to make changes then the firmware can be compiled and uploaded using the Arduino IDE with our board support package (BSP).



  • Download and install the Arduino IDE.
  • Add the following URL to the Boards Manager. File->Preferences->Additional Boards Manager URLs:
  • Install the Watterott AVR Boards via the Boards Manager. Further infos here. Tools->Board->Boards Manager….
  • Download the HDMI-Display Firmware.
  • Connect the USB Data port of the HDMI-Adapter (without display) to the computer.
  • On a Windows operating system a driver installation will be started. The drivers are included with the BSP or you can find them here.

Build and Upload

  • Start the Arduino IDE with connected HDMI-Adapter (without display).
  • Open the Arduino Sketch HDMI-Display.ino from the firmware ZIP archive.
  • Set the display and touch panel configurations in the file config.h
  • Select ATmega32u4 (16 MHz) under Tools->Board.
  • Choose the respective serial port under Tools->Serial Port.
  • Start build and upload: Sketch->Upload.
  • Wait till Done uploading. is shown.
  • On errors have a look in the Known Issues.


  • Disconnect the HDMI-Adapter from the computer and check the jumper settings (see schematics PDF file). Note: Wrong settings can damage the HDMI-Adapter and display.
  • Connect the display to the HDMI-Adapter.
  • Now you can connect the HDMI-Adapter with display to your board or computer.
  • If there is no output on the display or a flicker have a look in the FAQ.
  • If the red LED is blinking then no touchpanel was found. Check your cable connections and the firmware configuration in this case.

Known Issues

  • Serial Interface: When the red LED is blinking then the device is in error mode and the serial interface is deactivated.

  • Windows: Sometimes the driver for the USB Bootloader (Caterina) is not loaded correctly. This is the case when Done uploading. is not shown after the upload process. Check the driver state in the Device Manager, when the Bootloader is active (after the Upload is started). If you cannot install the driver on Windows 8 or higher then deactivate the driver signature enforcement. The Sketch USB device and the Bootloader USB device use the same caterina.inf driver file.

  • Linux: The Modem Manager detects the Serial Ports (e.g. Caterina Bootloader) as a modem and therefore a blacklist rule is needed. Run one of the commands - depending on your system:

    •   $ sudo nano /etc/udev/rules.d/77-mm-usb-device-blacklist.rules or
    •   $ sudo nano /lib/udev/rules.d/77-mm-usb-device-blacklist.rules

    and add the following lines to the file:

    ATTRS{idVendor}=="6666", ENV{ID_MM_DEVICE_IGNORE}="1"
    ATTRS{idVendor}=="1D50", ATTRS{idProduct}=="60B0", ENV{ID_MM_DEVICE_IGNORE}="1"

    Or you can also remove the Modem Manager from your system with:

    •   $ sudo apt-get uninstall modemmanager