Sorry, but I don't. If you have called $obj = Device::SerialPort->new(...), and not received a message telling you "can't open device: ...", then the port should be open and the handle obj->{FD} should be valid.

If the port failed to open during the new() call, then you would have received a null return from new() and your attempt to use $obj->{FD} in the call to binmode would have resulted in a "Use of uninitialized value in ref-to-glob cast at ..." message.

Without seeing the code you used, it is impossible to try and diagnose this further.