lane@cs.dal.ca (John Wright/Dr. Pat Lane) (09/09/90)
I have an interesting problem and I thought I'd put out and see if anyone's
considered it before.
We have a device that generates data and outputs it on a serial port to
a computer (IBM compatible) which captures and processes the data. We
want to hang a serial printer on the serial link so that the printer prints
everything generated by the device (actually, the device was originally
linked to the printer and we added the computer, but anyway...).
The first idea was simply to tap the serial, cable and connect the printer
"in parallel", so to speak. This actually works, after a fashion, but one
doesn't have to think about it too long to see problems - several lines
have two TTL devices on the same line that generate signals, sometimes of
opposite polarity and so on.
I sketched out a couple of circuits, one with a couple of OR gates on the
printers input lines. That, I presume, would allow it to listen to both
sides and isolate the two sides. I also drew a more complicated version
with ORs and AND gates that would (seemingly) implement the 3-way linkage
more fully. I won't waste bandwidth by repeating them here.
I'm not an engineer and both lack the knowledge to fully design anything
like this and would lack the resources to construct it. Perhaps someone
more knowlegeable than myself could suggest whether this is a valid
approach, etc. Perhaps some device for this is already available.
Would appreciate any help. Thank you.
PS: The traffic on this group recently went from astronomical to a trickle.
I suspect our System Admin. has been directling this stuff to /dev/null.
As such, please E-mail me a copy of anything you post on this matter.
Thank you.
--
John Wright ////////////////// Phone: 902-424-3805 or 902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8
Internet: lane@cs.dal.ca Uucp: lane@dalcs.uucp or {uunet watmath}!dalcs!lane