8-bitters and multi-whatever
Roy J. Tellason
rtellason at verizon.net
Wed Sep 12 20:00:44 CDT 2007
On Wednesday 12 September 2007 20:12, Ethan Dicks wrote:
> On 9/12/07, Roy J. Tellason <rtellason at verizon.net> wrote:
> > On Wednesday 12 September 2007 19:45, Ensor wrote:
> > > Hi,
> > >
> > > > You don't even need "rs232 levels".
> > >
> > > MIDI is a "current loop" interface isn't it?
> > Yup!
> > But my point is that in prototyping some small SBC the rs232 stuff is
> > about the only thing on there typically that needs other than logic power
> > (+5V) unless there's some analog stuff there on the board that needs it.
> And with MAX232 or DS275-type internal-charge-pump line drivers, you
> can get away with +5V only, unless, as you say, you need differential
> voltages for analog, or perhaps +12V for motors or something. For -5V
> at a few dozen mA, there's the venerable ICL7660 (an 8-pin DIP/SOIC
> and two external caps).
> For more sophisticated stuff, one can get isolated +/-5V or +/-12V or
> +/-15V potted modules, but those aren't typically required for
> microprocessor-type designs. We did have to stick a +5V->-12V
> charge-pump module on our Qbus COMBOARD, 20 years ago, because, IIRC,
> BA11 chasses provide +/-12V, but the BA23 does not (or was it some
> other MicroVAX chassis?) I still have a pad of them, but no real need
> for them since I prototype with MAX232s, not 1488/1489s.
That's fine if you were buying parts to build something, but having several
decades of accumulation on hand I'm more inclined to use what I have on hand
here, which unfortunately means 1488s and 1489s...
So if there's some easy way to do it otherwise, I'll probably go there. The
only issue is what to do on the peecee end of things...
Unless and until I get my hands on some of those other chips, maybe. :-)
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