Re: [CAD_CAM_EDM_DRO] Re: Lost Steps => time for microprocessors!

Jeff Barlow wrote:

>
> Hi again,
>
> Remember me, the guy with the old rusty Gorton on an island? I'm back
> home now and the mill's still on that island, to stay as far as I
> know.
> But that's beside the point.
>
> I feel much more in my element with this topic, though it's a lot like
>
> coming in late to someone else's design review meeting. I'll make a
> few
> quick points and get out of the way:
>
> 1. I must agree that trying to use a PC printer port to generate a
> nice
> even pulse train while running a GUI at the same time is a silly idea.
>
> 2. Trying to do it with a PIC class micro is sort of like trying to
> use
> a wrench for a hammer. It's a waste of a good wrench and it makes a
> really bad hammer.
>
> 3. I think Jon is on the right track here with the CPLD approach.

One very small correction here, but thanks much for the support. It is
hard to get
heard for all the PIC for everything people out there. A CPLD, which is
very nice for
a lot of simple things is just too small to hold the encoder counters,
or the timing
generator. It just has too many flip flops. If you have a 24-bit
counter, and a 24-bit
count holding register for each channel, plus one 24-bit word assembly
register, pretty soon
you have 216 flip flops on the chip, not counting any protocol state
machines and or
whatever else is needed. The CPLD I'm using on the DAC card is under
$10. The
more capable Spartan chip (about 5000 gate equivalent) is $18, and you
need a $4
serial prom to hold the program for it.

> Jon, are you doing this as a product design to sell, or is it an "open
>
> source" type project?

Both, I guess. What I'm trying to eventually get to, is where I can
supply an entire
package, with EMC software, just about any computer, and several boards
that
plug into a backplane to do encoders, servos or steppers, servo amps,
digital
I/O for auxilliary stuff, and eventually a dedicated control panel for
EMC.

> Also, I read about you doing battle with the EPP
> fast transfer protocol. How many different parallel port chips have
> you
> tested with. Some don't play nice at all.

Well, 2 so far. I never got EPP mode to work right. But, I did get one
system
set to ECP mode, and then configured that back to the EPP subset, and
that
DID work as advertised. I have to go back and try the first machine
again with
the new knowledge I've acquired, and the code that now works on one.
The ECP seems to be more strictly specified in hardware, where the EPP
definition left a lot up to the designers, as the only locked-down
interface
definition is the BIOS routines.

For a number of reasons, USB can not be used safely.

Jon