Re: [CAD_CAM_EDM_DRO] DeskNC Windows version

High speed I/O on the parallel port under Windows is not impossible. But it
is difficult to do a lot of calculations, timing and pump the data out under
Windows. The parallel port is just 3, 8 bit ports. You have hundreds of
other 8 bit ports in your PC screaming along at very high speeds under
Windows software control all the time.

The best way I know of to do this in Windows is by using a .vxd ( or wdm or
whatever it'll be called in the next versions of Windows ). The application
program reads the G codes and calculates the step commands. These commands
are handed off to the .vxd which runs at Ring 0 and has access to all ports
of the system without the usual restrictions of Windows. The .vxd handles
the timing and step / dir outputs.

Still, you are using the same processor to handle the .vxd as the control
program. A better approach is of course a dual processor system. One
processor handles the I/O .vxd and the other the control program.

Where the external box really shines, is the timing can be done on a
seperate microcontroller. This takes a big load off your control program.
This is the same reason the Ahha Artisian board has the timing circuits on
it's I/O board. It's like using the dual processor machine but the second
processor is out there at the end of your serial port.

The biggest limitation of this approach is the amount of data you can pump
out to the microcontroller due to the typical memory limitations of the
device.

While I've not built any CNC controllers from scratch in the last 8 years,
I've used this same approach to a lot of industrial control problems.

Flashcut does this with an 8051 family micontroller. They have a good
product but it's just too darn expensive. A VB program and an 8051 in a nice
plastic box for a grand! ( or is it more now ? )

Hopefully DeskNC Windows will be more reasonable.

later,
Larry E.

----- Original Message -----
From: "Alan Marconett KM6VV" <KM6VV@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, April 18, 2001 3:49 PM
Subject: Re: [CAD_CAM_EDM_DRO] DeskNC Windows version


> Hi Art,
>
> Thanks for the reply. I'd heard that parallel was impossible, and
> serial possible under windows. Is there any EPP/ECP support under
> windows? Might that work better, similar to serial? But then, it
> wouldn't be a "simple" parallel port, I guess!
>
> By 8000 PPS, are assuming a 133Mhz Pentium class machine on Windoz? I
> thought I'd heard higher numbers, must be for Linux or DOS.
>
> I'd also like to hear about the P6 instruction(s) that aid in
> timing/step generation.
>
> Alan KM6VV
>
>
> Art Fenerty wrote:
> >
> > Alan:
> >
> > When sending to a serial port from windows, you don't hang the
system
> > as much. You simply send a series
> > of commands and let the intelligent box do the rest. Most windows
software
> > suffers greatly when sending to the parrallel port due to the time
involved.
> >
> > ""Sounds like a FlashCut!"" -- It is, thats just how flashcut does it
for
> > the most part. It tends to make it very smooth and is a good solution
for
> > the money.Without a black box, you really can't get higher than 8000
> > Pulses/Sec.
> >
> > Getting Master5 to be smooth under windows was a real challenge and
it's
> > easy to see why Black box idea's are starting to proliferate. You just
can't
> > go faster than 8000 pulses per second without such a black box, although
> > that may change under the P6 series chips. My experiments show that
variable
> > asynchronous velocities are possible with P6 processors at quite a
speed. I
> > may try to implement such a system in a year or so. But it will take
awhile
> > for most peoples computers to catch up with the latest motherboards. I
have
> > enough problems with the number of people out there using 133's.
> >
> > Art
>
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