@J-Hilk yeah, thank you !

Ok, I have a mistake, in descriptorwitten signal I checked it new value, and if it is 0000, I disconnect from device.
But I checked the 1 index byte (the second), not the 0 index byte (first), and the second is always zero.
This is my byte order mistake.

@SGaist
Ah right - "configure" is ambiguous due to the two step configuration, once by the configure script for qtbase and once by the qmake for the other modules.
This is not so obviously that the summary of the configure script does not warn about disabled features in submodules due to missing dependencies.