What is IMail? Its unwrapped lines overflowed my Netscape "Reply"
buffer.
> it can be very difficult to tell when the computer and printers
> with bidirectional communications are talking to one another.
> Depending on the driver, there can be continuous status checking
> going on (e.g., drivers for some HP inkjets on Win type machines
> know when the printer is disconnected - this implies regular
> non-printing related communications)
I went to get my breakout box so I could monitor the lines on my printer
cable, but can't find the darn thing. I just had it last week. Can't
find my scope either. Will I *ever* get organized?
> >The bouncing should only occur during the time the
> >switch is actually being thrown, and should have
> >an effect (it should "bounce") in both directions.
>
> True. It's only how it is interpreted at each end.
> At the printer, strange control or data characters
> could be realized. At the computer, control that
> is unlikely to be understandable may result.
Good point. If the signal on the wire is 0 volts then there shouldn't
be any bounce-generated "spurious" characters, but since I can't find my
scope I can't tell you what the levels are or what's going on.
> I think the 500 series do not have much bi-di comms incorporated
> but the 600's (that were released right after) do.
Good info, thanks. I think the LaserJet II's preceded the Deskjet
500's.
> I think LaserJet II's are too old
Hey! They're younger than *I* am!
> >> HP for a while threatened to void warranties
> >> of those who used mechanical switches
>
> They also tended to insist that one use IEEE-1284
> certified printer cables (i.e. those that can
> handle bidirectional communications).
I would _love_ to see the IEEE-1284 spec on printer cables. Anybody
know where I can read it?
> > . . . then you ought to at least solder
> > some zeners onto the data lines.
>
> That ought to screw up the bidirectional
> comms pretty well. :-)
Well, if you solder them in *series* then it will!
But I meant to put them from signal wire to ground, so any transient
high-voltage spikes would be clipped and wouldn't zap the first
transistor at each end. MOVs might work too but I can't remember their
typical specs or what they cost. Basically you just want surge
protection that won't mess up the signals. I think there are
DIP-packaged zeners, meant expressly for this usage.
> >The debouncing is typically done with a "one-shot" circuit
> >on each data line which makes the switch look like it is
> >electronically closed even while it's still bouncing.)
>
> I would have guessed some sort of electronic latch
> but you're probably right.
A "one-shot" *is* an electronic latch, with a timed reset; it changes
state and holds the new state for a specific period, then resets to its
original state. You can make one from a 555 or pick up the appropriate
TTL chip (choose from several possible circuits) at Radio Shack.
> >> > - Electron Pete
> >>
> >> -Electric Rocky
> >
> >- Electron, The Duck :>>
>
> -Shockin Rock
- Beam Me Down Scotty, The Duck
("Very funny, Scotty, now beam down my feathers!")
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