RE: [CAD_CAM_EDM_DRO] Interface options, headless boxen, and remote control ...

Go for it, Larry! -

I only have one suggestion, and that is to look at the TI
TMS320LC2402 for your DSP. It has lots of on-board motion control
capabilities for CHEAP. I think they were saying $3-4 in 1k qtys.
They also have a flash version for $9.

This takes you to the TMSLC2402A:

http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumbe
r=TMS320LC2402A

This will take you to the product range page:

http://dspvillage.ti.com/docs/catalog/misc/dspparatable.jhtml?fami
lyID=322&_DARGS=%2Fdspvillage%2Fdocs%2Fcatalog%2Fmisc%2Fdsppfcrumb
let.jhtml.3_A&_DAV=322

HTH,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Larry Edington [mailto:ledington@...]
Sent: Sunday, August 19, 2001 12:25 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Interface options, headless boxen,
and remote control ...

RS-422 / 485 is still a serial device. There's just so much you
can do with
a serial
data stream with a UART or USRT that is decoded in the PC's I/O
space when
reading
and writing to a device at the end of the pipe. I've designed
motor
controllers using
RS-485 links with microcontrollers and they work great. But it's
not a good
design
for a CNC control.

I looked at microcontrollers hanging off a serial port. I even
built one.
Still it was
too limited by the serial pipe. Plus you have to rewrite the code
that's
already been
written to parse the G code and put the code to do the
interpolation out in
the micro.

I don't care at all for the parallel port either.
It's greatly limited and is a kludge for CNC due to the way it was
designed
for parallel
printers back in the early 80's.

A few years ago I designed an ISA card that provided a several 8
bit ports
and used a
37 pin connector like the Ahha card does. It used a simple PLD for
address
decoding.
That was good for several axis of I/O but still was limited by the
37 pin
connector. So
I added another 25 pin internal ribbon cable connector and added a
25 pin
slot mounted
connector. It was still limited by the fact it was just a dumb
I/O port.
All the load is on
the OS and host processor.

I've been looking at this for a few years. ISA was the way to go.
But those
days are
gone. ISA is a dead bus and is going away.

Welcome to the world of PCI. There are PCI parallel multiport
cards that
could
be used but you are still limited when you get into 4+ axis with
full limit
switches.

I've been kicking around the idea of designing a PCI card to do
CNC I/O
with.

So about a month ago, I decided to commit $$$ and time to it. The
card will
be a 32 bit PCI
card with lots of on board memory for step buffer, timers,
counters, encoder
interfaces,
spindle interfaces and lots of auxillary I/O. The design has been
started
and if all goes
well, in a couple of months I'll have the first prototypes
running. I'm
thinking 6 axis but
8 axis might make it in there. It will support steppers as well as
servos
and could even
be used to run steppers in closed loop mode with encoders.

I'm also talking to a DSP guru buddy of mine about adding a DSP
chip to it.
I'm not a DSP expert but can see how an off board DSP could help
in some
of the calculations CNC requires.

The PCI card will cable to a breakout box where all of the
connections to
the real
world will be. I'm kicking around the idea of an optical interface
to the
breakout box.
If not optical it'll be differential to the breakout box for noise
immunity.

I'm going to try to do it right. My hope is to end up with an
interface with
an open API
that anyone that wants to can write code or drivers for that will
be a
viable interface
for several years to come. But one that is affordable to build.

Linux and EMC is not my first priority. I prefer Windows. But I'm
sure I'll
find someone that
will be willing to write Linux drivers for it.

If nothing else, I'll finally have the interface I have wanted for
years.

later,
Larry E.