Re: control panel

[jmkasunich-at-ra.rockwell.com]

Ray Henry wrote:

> There are also better solutions for digital IO than a spare
> parport.  I just got a Measurement Computing (www.mccda1.com )
> DIO-24 PCI card for some tests here.  I am able to get Linux's
> /proc/pci to locate it for me and can use iosh to read and
> write to it.  This means that PCI boards should be able to
> be used in these kinds of projects.

> There are a number of ISA cards that will do similar tasks.
> One interesting (inexpensive) set of boards can be had from
> http://www.winfordeng.com/products/crd155b.html for less
> than $75.00 but I haven't had a chance to try them yet.
> This card uses a 25 pin parport connector and they have an
> inexpensive screw terminal interface card with some prototype
> area as well.

> There's got to be a good "industrial" approach to IO that
> gets us beyond the extra parport.

> Ray

What about the expanded I/O capabilities of the "EPP" mode of
most parallel ports?  Relatively simple external hardware can
allow a single parallel port to access up to 256 input ports
(2K digital inputs) and 256 output ports (2K digital outputs).
Software overhead can be quite low, and the hardware can be
very simple as well.  Two input ports and two output ports
(16 input bits and 16 output bits) would require two 74xx374s
and two 74xx244s, plus one or two glue gate packages.  Expansion
beyond two ports would require one '374 as an address latch, and
some decoding.  A pair of 74xx138s would be sufficient to decode
eight ports (64 bits of input, 64 output).

I believe this is what Jon Elson is doing with his PPMC boards
and universal motion controller.  I am planning several CNC and
robotics projects (if I ever get the time to work on them) and
EPP is definitely the way I am going to go.

Some good info about EPP is at:
http://www.beyondlogic.org/epp/epp.htm

John Kasunich