23 Jul
2010
23 Jul
'10
12:32 p.m.
On 7/23/10 3:16 PM, Tony Duell wrote:
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 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.
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.
Just out of curiousity, do the USB-parallel adapters
support all the
low-level bit-twiddling that you can do on a real PC printer port? Can
you treat them as 12 digital outputs and 5 inputs?
Not as far as I can tell - they are printer interfaces, not GPIO. I
have never considered them a replacement for a real parallel port, but 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.
-Dave
--
Dave McGuire
Port Charlotte, FL