Send break to device connected to serial port
For some devices, the break signal provides a way to clear the hardware buffer.
Before you can send a break to the device, it must be connected to obj with the fopen function. A connected serial port object has a Status property value of open. An error is returned if you attempt to send a break while obj is not connected to the device.
serialbreak is a synchronous function, and blocks the command line until execution is complete.
If you issue serialbreak while data is being asynchronously written, an error is returned. In this case, you must call the stopasync function or wait for the write operation to complete.