[GreenKeys] Smith Corona pc keyboard

[gil smith]

At 07:26 AM 1/7/03 -0500, you wrote:
>I did a project once to convert a generic
>PC kbrd scan codes to parallel ASCII using a microcontroller (Phillips
>87C750) - it wouldn't be TOO awefully difficult to convert an ITA2 loop
>to PC scan codes, plug your model 28 right into the keyboard port. I'm
>sure Gil could do it if he wasn't busy making a PDP-8 ;))


Hi Chuck:

Ha, that does sound like it's up my alley.  Actually, I did write some code
for a PIC micro to go into my TTY232 board.  Instead of the pc serial port
needing to talk baudot at the correct speed, the PIC gets jumpered in
between the 232 port and the tty loop.  It connects to the pc over a serial
port at 19200 baud ascii, and converts ascii to/from baudot at whatever
speed is needed.  Converting the tty chars to a higher speed for the pc is
simple enough, but for slowing the pc data down to tty speeds the PIC
relies on xon/xoff flow-control on the 232 port for (transparent) data
throttling.  So the tty just looks like an ascii 232 device at 19200 baud.

I suppose it would be easy enough to convert the tty chars to pc keyboard
scan codes and feed it into the kb connector, but it would be a one-way
hookup.

However, all this talk lately about tty gears makes me wonder whether folks
have a need for a gizmo to bridge two tty loops running at different
speeds?  I actually need to make a speed converter for 232 ascii since I
need to hook some slower-speed devices to higher-speed ports.  

It would easy enough to do tty-loop baudot speed conversion, to allow, say,
a 100-wpm machine to connect to a 60-wpm machine.  Of course, there would
no flow-control except an 80-char ram buffer in the pic, so dumping a
100-wpm paper tape to the 60-wpm loop would overflow the buffer.  But
typing on a 100-wpm keyboard would be fine.  And sending low-speed to the
higher-speed loop, even a tape dump, would also be fine.  Anybody care?

gil


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