21 Jul
2010
21 Jul
'10
12:53 p.m.
I do think that providing moderate amounts of power
along _a_ serial
interface is a handy thing. There's a pseudo-standard to do that for
Agreed. And on a parallel port. Many times I've wanted to invert a
signal, or latch a signal, or add a monostable between trobe and busy,
or.... And I wish I could power the extra IC from the port connector.
However people will alwayus try and draw more power than they should from
such things, so perhaps a power pin on the serial or parallel interface
would be more trouble than it's worth.
That said, some older HP terminals, HP9000/200 machines (and their serial
interface cards like the 98266 and 98268) have a 50 pin microribbon
connecoter for the RS232 port. Pins on that connecotr carry +5V, +12V and
-12V power lines. They're intended to power various add-ons (current loop
converter, HP network inteface, 300 baud modem, etc), buit they're handy
for homebrew stuf as well.
-tony