[TI-H] Re: Serial Link + Calc Freeze = ?


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[TI-H] Re: Serial Link + Calc Freeze = ?





On Tue, 10 Apr 2001, David Knaack wrote:

> From: "Gary Marsh" <gmarsh@thezone.net>
> > I drew up both circuits in SPICE, and created models for the TI link port
> > and EIA232 serial port.. and simulated both link designs. And found out
> > that neither!! of these two links put EIA232 compliant voltages on the
> > serial port.
> 
> heh, should be able to tell that by looking at it :)
> Fortunately most hardware is pretty good with out of
> tolerance values.  However, I suspect many of the problems
> that people run into are a result of less-tolerant hardware
> (and shoddy construction and ill-fitting parts).

Yeah, I've got doubts about circuits that use LED's for voltage
references, and such..

> > So, I designed/built this circuit, which works fine in SPICE:
> 
> Cool, do you have a PCB layout for it?

Nope. I don't make PCB's that often, and plus you'd basically have to
create a new PCB depending on what size of DB shell you put it in, what
manufacturer of shell, etc. I just "air-wired" mine into a db9 shell.  
Ideally, you'd put this guy on a double-sided, surface-mount PCB. But,
that's beyond the scope of the average hobbyist.

The circuit's so simple though, it's no sweat to make your own design.

- GM





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