I have a non-FSUIPC application on my P3D client PC that emulates an FMC/CDU. I have an OpenCockpits CDU I want to use.
The app sends out a code "0X00" to each USB to find the CDU connection. The app expects the code "FMS1" in return to establish a connection. Once the connection is made, the app expects keyboard key input to "click" the buttons.
I know how emulate the button press thru SIOC but can't find how to read and reply thru the USB. There is no FSUIPC or defined Add Ons (e.g. PMDG).