Hi Daniel,
There is not an easy way to do this. If there were, it would be the same way LabVIEW would normally access the parallel port, which is through NI-VISA. However, NI-VISA for LabVIEW RT does not support parallel port communication due to limitations of the OS drivers. In Windows, the default serial driver that VISA uses conveniently supports the parallel port through the same driver. But in the Real-Time OS, the default serial driver only handles the serial ports, and not the parallel port.
There is an excellent tutorial that talks about this:
Using the Parallel Port in LabVIEW
http://zone.ni.com/devzone/conceptd.nsf/webmain/72c6fc6ce4ad4d1386256b1800794596
However, generally speaking (whether your using LabVIEW or LabVIEW RT) it is possible to communicate with the parallel port using registry level programming. The low-level functions "In Port.vi" and "Out Port.vi", that ship with LabVIEW 7.0 and above, are examples of this (in LabVIEW, see the shipping example "Parallel Port Read and Write Loop.vi"). The trick is to find the base address for the parallel port, which isn't nearly as easy on a real-time OS as it is in Windows, since there's not a "Printer Port Properties" page that you can look up the addresses in. In fact, I am not sure how this would be done on a real-time system.
Unfortunately, registry level programming is not a feature that we can support, but this is the best method of going about doing so if you can figure out the registry addresses on your Real-Time target.
Regards,
Jeff M.
Applications Engineering
National Instruments
