readme

fsmlabs的real time linux的内核

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 the
second realtime or non-realtime box. so you might have to recompile on 
that second box manually if the instalation (especially the libs) are not
the 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_lpt

files:

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 .