Command processing and timeouts

Commands may be sent to the logger via either the USB-CDC port or a true serial port (RS-232 or RS-485).  With a few exceptions and minor differences, both ports are intended to offer the same functionality, but can not be used for command input simultaneously.  If this is attempted, then either one of the ports will not respond, or there will be a 'busy' message:

E0101 command parser busy