Low Level Parallel Port IO
From MobileRobots Research and Academic Customer Support
Robot onboard computers include a parallel port interface. In addition to communicating with devices using a data stream over the parallel port interface, it is also possible to access the port's low-level signals at will for TTL digital IO.
While the onboard computers contain parallel port interfaces, they do not generally come with standard 25-pin D-type plugs. Refer to your computer's manual for locations of parallel port interface pins on the main computer board.
On Linux, the parapin library or parapin kernel module may be used. For more information, see http://parapin.sourceforge.net/. See also http://www.faqs.org/docs/Linux-mini/IO-Port-Programming.html
See also http://www.beyondlogic.org/spp/parallel.htm .
MobileRobots does not endorse or support these products specifically. For help with these libraries, contact their respective user or development communities. Be aware of the limitations of the parallel port interface-- use low amperage signal levels only. If in doubt, contact an electronics expert.