Re: servos

One possibility to consider is using ide controller ports. Auxilliary
controllers are cheap, they are very fast and easy to deal with in software.
You do not have to implement a device-side protocol (as in USB or SCSI), ide
is basically a decoded mezzanine bus that is buffered from the actual CPU
bus.

It is still only 8 bits wide, but it much faster than a parallel port. If
you use an ISA bus card, the signals are slow enough to use an 8255 to
generate 24 usable i/o lines. If you use PCI/motherboard ide controllers,
use fast 373's/245's to generate extra ports.

If there is interest, I can do some testing, and generate a tested PCB
layout/schematic (for free distribution). I have been thinking of building
an external stacking bus (physically like pc104, but with pre-decoded board
selects, etc) using an ide port.

Dean

----- Original Message -----
From: David Howland <dhowland@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Friday, September 24, 1999 4:49 PM
Subject: RE: [CAD_CAM_EDM_DRO] servos


> From: David Howland <dhowland@...>
>
>
>
> Yes, the Interfaces which are low in cost will place restrictions on
performance, and <real time> goes first, and therefore the speed is
limited. This improves with faster computers, but this scheme probably will
not work on a system with a red hat sitting on top. Still the USB is
available on most newer machines and might play a role of interest to some
exploring their personal interests herein.
>
> The funney part of the converging technologies, may be that as computers
get faster and cheeper, the standard interfaces may begin to work in ways
they were too slow for in the past. Metal will not get softer and easier to
machine as time goes on.
>
> As far as the printer interface goes, I'm thinking of the dual printer
interface card option, giving you 16 bi-directional lines of data, plus an
odd amount of handshaking and status lines between the two parallel ports
available. If you look in your favorite cheep computer catalog, you find
all sorts of standard I/O cards to drop in a slot. It seems to me that the
fancy cards such as Servo to go give you a lot of bang for more bucks.
If you can live
> with less bang, then why not consider the concept that while you are even
thinking about it, computer I/O in the standard formats will be 6% cheeper
by the time you order it.
>
> >
> > Computer Interfacing cards and approximate price:
> > ISA SCSI-II Controller card $50
> > PCI USB I/O Card $40
> > Dual port ISA Bi-directional Printer Card $35
>
> [David Howland]
>
> <In response to comment from Jon >
>
> USB is a real exciting option, but I wonder, how long does it take for a
request from a R/T module to be sent
> through the USB driver to the custom motion box, and then for a reply to
come back through the driver to the
> R/T module. Actually, that can't work, anyway. So, if the R/T module had
the code to manage the USB,
> then nobody else could use it. Maybe with that restriction that the USB
couldn't be used for any other purpose,
> maybe this would work.
>
> Same problem, then, with the SCSI interface, it would have to be a private
resource to the R/T code.
>
> And, the printer interface is just too narrow (8 data bits plus way too
few control lines) to be a good
> data path. Also, there are limits on how many printer ports you can have
(unless you hack the address
> decoder).
>
> Jon
>
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> [Attachments have been removed from this message]
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> > Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the
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