Re: Interface for CNCPro, etc.

> Suppose I design a card that will fit in one ISA or PCI slot that has
> optoisolation, 5V isolated supply for outputs and a screw terminal strip
> that sticks out the back for direct connection to amps, switches and aux
> I/O. No interface cards to make, no pullup resisters to find a home for, no
> breakout boards to buy, no 25 pin DIN connectors or cut-to-length serial
> cables to fiddle with. Just connect the amps, switches and I/O to the back
> of the PC and go.

A couple of ideas:

I've given some thought to building a board to carry a couple of the
encoder interface chips (Tom Kulaga / Dan Mauch style) as well as an
8255 for general purpose I/O when the parallel port is insufficient.
I was just going to socket the chips and use them as spike absorbers,
but I suppose optocoupling could be done. There are logic-level
optocouplers that should probably pass clean signals at 100khz. The
various inteface chips could be populated or not as desired. in
having standard off-the shelf cables coming from the card, so that the
computer can easily be disconncted from the amps. Then have simple
passive breakout boards that could mount in the amp enclosure and go
from DB25's or whatever on the cable to screw terminals.

Are you sure the parallel port can't drive an optocoupler? It may not
be in spec, but I've never had any problem driving visible LED's from
one. If it weren't for the power issue, I think an optoisolated
parallel port breakout board might not be a bad idea.

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
30 Griswold Street, Cambridge, MA 02138
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