LabVIEW has VISA, a general purpose interface tool, and CLASSIC serial port handlers.
VISA is more efficient at runtime, but requires drivers to be installed (if you build an executable to be run outside the development system).
CLASSIC drivers use the built-in serial handlers.
No DAQ card is necessary, unless you want more ports than are built in to your system (I've programmed a system with 32 serial ports).
Use VISA CONFIGURE SERIAL PORT to specify baud rate, parity, etc.
Use BYTES AT SERIAL PORT to detemine how many bytes have been received.
Use VISA READ to fetch that number of bytes.
Use VISA WRITE to output bytes to your device.
