Re: [NTLK] FDTI usb

From: Humphreys, David (
Date: Tue Dec 07 2004 - 05:30:30 PST

In answer to Jake Borden's questions...

> A SER-001 type board (USB-001?) would certainly be possible. The
> SER-001 has a full AppleTalk and local talk transceiver on it,
> and I'm not exactly sure why. If we were adding a full
> second port to the thing then it might make some sense.
> However, the SER-001 if I recall is just an alternate
> connector to the first port. In this case, why doesn't it
> just use the first port's transceiver? I'm not too familiar
> with apple/local talk. Maybe this configuration allows both
> the original port and the new DIN port to be active at the same time?

In order to make the board as user-install-friendly as possible it was necessary to use the internal connector.
Unfortunately, this connector doesn't carry the buffered output from the AppleTalk chip but rather the raw inputs from
the Cirrus asic. These are logic level signals that I would not want to appear on an external connector for someone to
short out.

Also, some of the signals are inverted.

Using the LTC1328 might seem unnecessary at first glance but it fitted the application perfectly as it was simply a
duplication of the main board mounted one and isolated the Cirrus chip from the bad, bad outside world.

It would have been a lot easier if the output of this chip appeared on the external connector but... Oh well!

> A USB-001 daughter board would probably only expose
> Serial-over-USB functionality anyway.

Without a major rewrite of the OS that is probably true. Serial over USB is of course possible as evidenced by the
keyspan adaptor.

> Does anyone know why the designer of the SER-001 opted to
> expose port 0 again rather than port 3? Was port 3 ever
> exposed in software? Does anyone have a pinout for the
> internal connecter used by the SER-001?

Well let me ask him...

The SER-001 was meant to alleviate the mechanical destruction of the external connector. It provides a more standard
mini-din connector without the need for a dongle. Most software uses port 0. Why make things difficult?

Port 3 is exposed in a limited way. The keyboard can use it.

The internal pinout is available on UNNA.

> My guess is that the internal port that the SER-001 connects
> to has some sort of pin that you pull to 5v (or gnd) to
> indicate that the internal serial port (modem) is available.
> This, coupled with the FDTI chip and a USB connector out the
> back, and you're good to go.

Yes, it has such a pin. You can toggle between internal and external using it.

> seems like a potentially cool project.

And one that I have investigated.

It is hard to find time to devote to these projects. I have a lot going on in my life at the moment and other Newton
projects are sitting on my workbench...



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