For using the RC-Controls over an USB-Serial converter it is very important to support COM1 to COM16 instead of theoretically COM1 to COM4 (in global.cpp).
Now I am able to use the Dragonfly4 RC-control (ZhenHua5 protocol) only on COM1!
Reason: Every USB serial converter (USB-serial converter, laptop onboard modem, hsdpa modems...) get for each USB port it own COM number. In not every case it can be set to COM1!
I have written a description to set the usb serial converter to COM1!
lg
Alexander Lindert
added serial interfaces