> What is strange though, is that the "bad" cable works fine if I
> plug it into the dongle first then the Interconnect adapter.
> It's only when plugged directly into the DIN-9 connector on the
> SER-001 that it fails to work. To. wit.:
>
> +--------------------------------+---------------+----------+
> | | Cable A | Cable B |
> +--------------------------------+---------------+----------+
> | into Dongle/Interconnect Port | Works | Works |
> +--------------------------------+---------------+----------+
> | into SER-001 | Doesn't Work | Works |
> +--------------------------------+---------------+----------+
>
> I can't imagine why the cable would only be "bad" when plugged
> in directly and not through the Dongle. Any guesses?
Cable 'A' could have some damage to its' mini-din plug. Check for
bent or flattened pins. Even slight damage that may go unnoticed
at first, could be the culprit.
Now I am assuming the two cables are the same? If not, they could
be wired slightly differently.
> Maybe the
> "dongle" has an AGC that's compensating for a weak signal on one
> of the pins? Or something goes on in the signal path through the
> Interconnect port that results in a marginal signal getting
> cleaned up?
Nope. The dongle is only a transitional adapter.
> It sounds far-fetched but I can't think of any other
> explanation. Maybe if I get really curious I'll check the signal
> levels on each pin of "cable A" with a multimeter and see if one
> is out of whack...
A multimeter won't tell you very much. You could measure the continuity
of the wires in the cable and map them to the pins on each end.
You could see the presence of signal activity on the lines but it
would be difficult to come to any conclusion using just a multimeter.
An oscilloscope would be far more useful as you could 'see' the signals
as they change.
The serial port has several things going on at the same time or in quick
succession. A good knowledge of serial protocol would be useful.
Based on the evidence presented thus far, I would suspect the interface
between the cable mini-din plug and the SER-001 mini-din socket.
As cable 'B' works all the time, I would be concentrating on cable 'A'
mini-din plug.
> Anyhow, it appears I now have a dongle-free Newton and all signs
> indicate it's working as expected. If this holds out, I'll be a
> very happy Newtoneer indeed!
>
> Any comments, ideas, theories welcomed.
>
> -Jeremy
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