I see.... So
considering all the things I (and others) have made that
link to PC parallel ports and which _don't_ use the centronics protocol,I
can think of yet another reason not to downgrade to a modern PC.
Well, as with lots of other things, there are ways around this. One
Of course there are ways to do it.
of the FTDI chips can easily be used for digital
bit-twiddling, and
there's at least one free library out there with great support for such
twiddling.
Here's a good (brief) description of it, along with a $15.00 breakout
board that's got two rows of 0.1" pins on each side and a USB connector
on the end:
http://www.sparkfun.com/commerce/news.php?id=386
This is really good stuff, give it a shot.
OK, and what would I connect the USB port to?
I'm all for poo-pooing new stuff when it really isn't useful for
anything real, but poo-pooing just for the sake of poo-pooing is bogus.
Seriously.
Sure...
But there is a tendency for some people to assume that because something
is new, it must be better than what came before. And a second related
assumption is that becuase something is superior for some uses, it must
be superior for all uses.
I must admit that I tend to go too far the other way on the first
assumption, and am much happier sticking to what I already know and
understand. But anyway.
Something is an upgrade to me if it makes mu life easier. It's a
downgrade if it makes it harder. And using a complex IC and a speical
library seems to eb alot harder than sending some values to I/O ports on
a board with ahandfull of TTL parts on it. We can argue about relaibility
too. And repairability. If I mis-conenct a port pin on that FTDI chip and
burn it out, I'm out $15 + shipping. If I misconnect a pin on a PCB
printer port, I have a simple TTL chip to replace that is <$1.
Actually, I don't doubt that USB is a fine interface for _some
applications_. The falicy is to try to use it for everything. One thing I
objected to majorly was a requirement (from Microsoft I beleive) that a
PC would only meet some specification if it _didn't_ have RS232 and
parallel ports. BLETCH!. By all means have USB ports, but have a parallel
port and a couple of serial ports _as well_. That would seem to satisfy
everyone.
Actually, do the USB-RS232 adapters (I refuse ot
say USB-serial, since
there are many, many serial interfaces, including USB itself) allow you
to do all you can do with aa PC Async port? Like setting odd baud rates?
Or 5 bit mode (yes, I do sometimes want to talk to ta Creed 7)
Some support more than others. For example, USB<->serial adapters
based on the Prolific PL-2303 chipsets (apparently) cannot generate a
break, while my Keyspan units can.
Do they support 5 bit words? Do they support strange baud rates?
-tony