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).
https://github.com/watterott/Arduino-Boards/raw/master/package_watterott_index.json
HDMI-Display.ino
from the firmware ZIP archive.config.h
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