I'm just starting out in b4a, I need to bit-bang the port but USB serial 2.4 does not support setBreakon, setBreakoff but the library is based on mik3y: USB serial for android open source project, as of version 3.3.0 setBreak is supported. Is it possible to add support for setBreak on Usbserial 2.4
It is an interesting upgrade but not a trivial one as it requires a large rewrite of the library. It looks like the developer refactored the library in v3.0.
It will happen at some point.
There are two related libraries, felUsbSerial and UsbSerial. They don't support the setBreak feature but they do support ch340 and probably the FTDI chip as well.