Thank you.
I read (learn) the booklet, browsed the forums, tried to configure several paths with several examples of programs and libraries for usb : nixie counter, usb-serial-for-android-master and also usbserial example, however B4A does not recognize not the library path. I also tried with zipped libraries, including the libraries in the B4Xlib/files folders, etc... but il wrong.
The installed version of B4A is version 10 on an old win10, 32 bit laptop with 2GB of ram.
Windows 10 is up to date, this computer seems to work correctly.
For using this computer with B4A i change MaxRamForDex to 1024
Regards.