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'[ot]: oscilloscope pulse display'
2003\01\22@154449 by rad0

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just FWIW

I have checked the pulse, on the parallel port of an older PC
running win98, using a CNC program,

and the thing puts out a very nice 5volt square wave, it glitches once
in a while, I guess this is the noise spoken about, but it is doable to
do this in windows, or was....

then checking my simple program again using a delay, it was no
better, it seems that if you remove everything except the statement
which turns on the pin, it will change it from 0 to 5vdc, but something
turns the pin off again automatically, some windows feature or function.

So, like somebody said, it's back to the API or write another dll or
what ever,

If any of you know the solution to controling pins on the parallel port,
your help is appreciated....


thanks

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2003\01\22@175428 by Herbert Graf

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>>I have checked the pulse, on the parallel port of an older PC
running win98, using a CNC program,

and the thing puts out a very nice 5volt square wave, it glitches once
in a while, I guess this is the noise spoken about, but it is doable to
do this in windows, or was....

then checking my simple program again using a delay, it was no
better, it seems that if you remove everything except the statement
which turns on the pin, it will change it from 0 to 5vdc, but something
turns the pin off again automatically, some windows feature or function.

So, like somebody said, it's back to the API or write another dll or
what ever,

If any of you know the solution to controling pins on the parallel port,
your help is appreciated.... <<



Which version of windows are you using? For any version of Win9x (including
Me) I haven't had any problems with manipulating the ports manually (I use
inline assembler to do it). For WinNT (including XP and 2K) you need a
driver to allow direct access to the port. Harder, slower, but doable. You
could always write your own driver if you really needed the speed, but
that's in the realm of "crazy talk" IMHO (writing drivers for windows is NOT
fun). TTYL

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2003\01\22@183748 by Kyrre Aalerud

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Can't you use DMA or similar to send a pulsetrain to a port at a specified
speed?
I recall something about this from my old soundblaster playback days using
dual buffers etc...  That was dos, but I still wonder.

   KreAture

{Original Message removed}

2003\01\22@194041 by Jake Anderson

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you seem to be using VB you may be able to use the comms control
(mscomms control ver1) select the parrallel port and then "send" a binary
code representing the bit toggle you want.

also you might wish to slow your transition down somewhat. (the fastest i
have heard of successfull bit bashing of a parrallel port is about 80Hz
though this was PWM'ing on a 486 PC104) there are several methods of doing
this. the timer controll is only good to about 50msec i think and its
inaccurate but it might do to get some result. otherwise you will windup
useing the high performance counter and a loop to get accurate controll.
assuming you are using VB
create a timer on your form set its interval to 10
in the timer control

private sub timer1
   Static OutPutVal As Integer            'static var so the state is
maintained from call to call
   If OutPutVal = 0 Then OutPutVal = 1 Else OutPutVal = 0      'toggle the
state
   DlPortWritePortUchar &H378, OutPutVal                             'do
the funky stuff
end sub

also i'd suggest just trying to set the value manually ie turn it on then
wait a while and turn it off
{Original Message removed}

2003\01\22@204419 by Bob Ammerman

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You need a device that makes DMA requests. A vanilla-type parallel port does
not do that.

For the fun of it I wrote a little assembly language program to directly
toggle the LPT port. When running under Win98se it was certainly very
glitchy as windows and interrupts took the processor away from it. Note that
even in Win9X access to the port is not direct. Rather, it is virtualized by
a VXD. Besides the glitchyness caused by windows there was quite a bit of
jitter that I attributed to the hardware.

I then ran it under MSDOS 6.22 and it was better, but still a little
glitchy, and no less jittery.

Finally, I added some code to disable all interrupts while it ran and that
cleaned up the glitchyness, but not the jitters.

Bob Ammerman
RAm Systems

{Original Message removed}

2003\01\22@210835 by Scott Stephens

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From: "Bob Ammerman" <spam_OUTrammermanTakeThisOuTspamADELPHIA.NET>
Subject: Re: [ot]: oscilloscope pulse display


> For the fun of it I wrote a little assembly language program to directly
> toggle the LPT port. When running under Win98se it was certainly very
> glitchy as windows and interrupts took the processor away from it. Note
that
> even in Win9X access to the port is not direct. Rather, it is virtualized
by
> a VXD. Besides the glitchyness caused by windows there was quite a bit of
> jitter that I attributed to the hardware.

Did you consider demanding priority by writting your own device driver, and
running 'ring-0' ? That is something I'll probably look into, another day.

Scott

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