[visionegg] pseudorandom

I am trying to get a length 511 pseudorandom m sequence to control the
phase of a checkerboard. The two checkerboards are preconstructed. CC is
one checkerboard. CP is the counterphase checkerboard. I also want a
signal that shows the checkerboard phase. Here is the control script
that I am using

LPT1 = 0x378 

def control_dynamic(t):
        
        if t<= dynamic_time:
                
                tt=(int(t*100)%511)
                
                if ps[tt]== 0:
                        dynamic_texture_object.put_sub_image( CC )
                        data = 0x00
                        raw_lpt_module.out(LPT1,data)
                else:
                        dynamic_texture_object.put_sub_image( CP )
                        data = 0xFF 
                        raw_lpt_module.out(LPT1,data)
        
                
p.add_controller(None,None,FunctionController(during_go_func=control_dynamic))
        
p.go()


There are two problems.

(1) tt=(int(t*100)%511) does not give an ordinal sequence. For example
it gives 0,1,2,3,4,5,7,etc  skipping up every 6 to 7 positions.I
understand why but I have not been able to find a way to get a counter
going within the control loop. If I try a statement like cnt=cnt+1, it
increments once and that is all.

(2) every once in a while the screen stops updating the display, usually
with one or the other checkerboard displayed statically
or on occasion with a blank screen. However, LPT1 goes on happily
changing. I can get the screen to resume displaying the checkerboards
if I move the mouse around in the "Konsole" window. If I keep the
"Konsole" window visible and keep the cursor in it, the display does
not stop updating.


I am using an Nvidia board and the displays are free of any tears
and refreshing at 85 Hz.

I am operating with Fedora Core 2.

Thanks for any help you can give me

Dick Srebro

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