examples/parallel:Files in this directory are for playing with the parallel port and rtlinux , to use them all you will need a standard PLIP-cable . For details on that cable pleas check PLIP.txt.note: the values of LPT is not defined via common.h for read_lpt.c and lpt_irq.c since I assume that you are running these two executable on thesecond realtime or non-realtime box. so you might have to recompile on that second box manually if the instalation (especially the libs) are notthe same. to manually compile read_lpt.c and lpt_irq.c use:  cc -Wall -O2 lpt_irq.c -o lpt_irq   cc -Wall -O2 read_lpt.c -o real_lpt note: to compile these progs for MiniRTL you must take the lib restrictions into account , that is if you installed the glibc-2.0.7 package ,then you  need to issue the compile command as:  cc -Wall -nostdlib -L /usr/lib/glibc207/ -lc -O2 lpt_irq.c -o lpt_irq   cc -Wall -nostdlib -L /usr/lib/glibc207/ -lc -O2 read_lpt.c -o real_lptfiles:rt_irq_gen.c : wait for an input on the parallel port . So this is               poling in a busy-wait loop until somthing occured at               the parallel-port. It will "freez" your rtlinux box               until something comes in or it is timed out. if you               remove the timeout in rt_irq_gen.c then your rtlinux box               will only stay "alive" aslong as you run the lpt_irq                programm on your second linux box conecting it via a                plip-cable to your rtlinux box.sched_toggle.c : This toggles the pins D0-D7 of parallel-port. with an                  oszilloscope you can directly measure the scheduling 		 jitter of RTLinux ! With the program read_lpt running on                  a second linux (rt or non-rt), you can watch the pins toggle                 (but you will get no timings...)                 rectangle.c: The name says it. this is two threads , each sets D0-D7 high the  	     then low. as the two threads are running with different periods             one gets a phase-change at every period of the slow thread so the             output is only a pure rectangle if the second thread is disabled.read_lpt.c: This is a small programm that will simply read the status pins of 	    the parallel-port in a loop. you can use this instead of an 	    osziloscope just to see what is going on , to do so start this 	    program on a second Linux pc and connect the rtlinux box via	    standard PLIP-cable (they are not expensive its not worth making	    your own, if you connect wrong pins you can damage your paralell	    port...)lpt_irq.c: This pools for ACK to go low on LPT and then toggles pins D0-D7 to	   produce an ACK . again this runs on the second linux box and is 	   connected to the rtlinux box via PLIP-cable .