cassette tape interface, terminal, etc.

[Allan Adler]

I haven't quite given up on building the Z80 computer described by
Ciarcia in his book, "Build your own Z80 computer". On the other hand,
there are lots of details I still need to understand and also lots of
things have changed since he wrote the book. One thing I'm hoping has
changed is cassette players. The old one I have can't be started or stopped
or controlled other than by pressing the mechanical buttons, which probably
work through levers. So I don't hold out much hope for being able to modify
it so that it will start, stop, play or record or change its volume level
under computer control. (If I'm wrong about that, I'd like to know how to
do it.) The alternative is to obtain a cassette player that can be controlled
by electrical signals instead of push buttons, but I don't know how expensive
they are or where one gets them, maybe used. If it isn't dirt cheap, it isn't
worth it. (I've heard of e-bay but I'm not ready for that.)

Another peripheral that Ciarcia talks about is a CRT terminal. After reading
what he has to say, I eventually realized that he was not explaining how to
build a terminal, only how to build an interface from it to the computer he
wants you to build. Terminals have changed a lot and the ones he had in
mind have probably gone the way of the dodo. I recall that old computers,
such as the Timex-Sinclair, had a TV interface which let you use your
TV for a terminal using a game adaptor. Ciarcia doesn't seem to explain
how to do that. But maybe TV's have changed so much that one can't do it
that way either.

One can still get Z80 chips, so I guess my questions, stated and unstated,
might boil down to this: how would one update Ciarcia's book so as to make
home made peripherals with ingredients that are available today?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

 

[Wade Hassler]

Allan Adler <ara@nestle.ai.mit.edu> wrote in message news:<y93islooitr.fsf@nestle.ai.mit.edu>...

I haven't quite given up on building the Z80 computer described by
Ciarcia in his book, "Build your own Z80 computer". On the other hand,
there are lots of details I still need to understand and also lots of
things have changed since he wrote the book. One thing I'm hoping has
changed is cassette players. The old one I have can't be started or stopped
or controlled other than by pressing the mechanical buttons, which probably
work through levers. So I don't hold out much hope for being able to modify
it so that it will start, stop, play or record or change its volume level
under computer control. (If I'm wrong about that, I'd like to know how to
do it.) The alternative is to obtain a cassette player that can be controlled
by electrical signals instead of push buttons, but I don't know how expensive
they are or where one gets them, maybe used. If it isn't dirt cheap, it isn't
worth it. (I've heard of e-bay but I'm not ready for that.)

Another peripheral that Ciarcia talks about is a CRT terminal. After reading
what he has to say, I eventually realized that he was not explaining how to
build a terminal, only how to build an interface from it to the computer he
wants you to build. Terminals have changed a lot and the ones he had in
mind have probably gone the way of the dodo. I recall that old computers,
such as the Timex-Sinclair, had a TV interface which let you use your
TV for a terminal using a game adaptor. Ciarcia doesn't seem to explain
how to do that. But maybe TV's have changed so much that one can't do it
that way either.

One can still get Z80 chips, so I guess my questions, stated and unstated,
might boil down to this: how would one update Ciarcia's book so as to make
home made peripherals with ingredients that are available today?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************

The computer's design probably includes a relay to switch the cassette
motor on and off: if so, you just need to find the player's motor
lead, break it and install a connector of some sort and a matching
plug from the relay contacts.
As for the CRT terminal, a PC running any terminal emulator
(Hyperterminal, TeraTerm etc.) will do the job.
Wade Hassler

 

[Michael Black]

Allan Adler (ara@nestle.ai.mit.edu) writes:

I haven't quite given up on building the Z80 computer described by
Ciarcia in his book, "Build your own Z80 computer". On the other hand,
there are lots of details I still need to understand and also lots of
things have changed since he wrote the book. One thing I'm hoping has
changed is cassette players. The old one I have can't be started or stopped
or controlled other than by pressing the mechanical buttons, which probably
work through levers. So I don't hold out much hope for being able to modify
it so that it will start, stop, play or record or change its volume level
under computer control. (If I'm wrong about that, I'd like to know how to
do it.) The alternative is to obtain a cassette player that can be controlled
by electrical signals instead of push buttons, but I don't know how expensive
they are or where one gets them, maybe used. If it isn't dirt cheap, it isn't
worth it. (I've heard of e-bay but I'm not ready for that.)

You do realize that most cassette-based computers had extremely rudimentary

file capability. It was not a particular burden to press the buttons on
the cassette recorder. You wouldn't be doing it that often, and virtually
none of the computers had the software to seek out a given file, or do
rewinds, or whatever. You would not be sorting or filtering files back
to tape, merely loading and saving results of a program or saving
and loading a whole program.

You'd take that portable cassette recorder that you had sitting in the
closet, and hook up the audio lines to your computer. If there was a volume
control on the thing, you'd do some testing until until you got the levels
right, and then you wouldn't have to fiddle with anything on an ongoing basis.

Many/most cassette interfaces had a separate line for controlling the motor
on the cassette deck. You'd plug it into the then-common "remote" jack on
the recorder, which existed precisely so you could start and stop the
tape movement. So you could position the cassette to the point you want it,
press the "play" and "record" buttons, but the tape isn't advancing until
the relay kicks over.

You'd get short tapes, like ten minutes long, or use regular length and
just save one file per tape. That way you didn't have to deal with
fastforwarding and finding a specific file.

One in a while, someone would come up with a very fancy tape operating system,
and they did require a fancier tape deck, but those were rare.

If you're still not convinced, then the fussier would find the innards
from fancier tape decks. Raw transports intended for use in computer
equipment, which were electronically controlled. They'd find them in
the surplus stores, and put them to use.

I also have a recollection of one NEC tape deck intended for personal
computer use that was electronically controlled; at least my recollection
is that the buttons were not mechanically linked to the transport.

If you want a fancy tape deck today, then go to garage sales and rummage
sales until you find a full blown audio tape deck that does have
electronic buttons, and then start modifying it until you can control
it remotely. But realistically, you won't need it.

You might want to give consideration to moving to a floppy drive.
Those were rare back then, but one company put out a hybrid. They used
the drive much like a cassette recorder, and did not bother with
much of an operating system. You'd tell the program where on the floppy
you wanted to save it, and write that down on paper. There was no directory
on the floppy, and you were dealing in terms of sector and track number,
much in the way you'd write down the tape counter on the cassette deck.
By moving to floppy, you'd get your remote capability, and faster
save and loading of files, but without the finicky-ness of the of
the cassette, and without the trouble of a full blown operating system
to deal with the floppy.

Another peripheral that Ciarcia talks about is a CRT terminal. After reading
what he has to say, I eventually realized that he was not explaining how to
build a terminal, only how to build an interface from it to the computer he
wants you to build. Terminals have changed a lot and the ones he had in
mind have probably gone the way of the dodo. I recall that old computers,
such as the Timex-Sinclair, had a TV interface which let you use your
TV for a terminal using a game adaptor. Ciarcia doesn't seem to explain
how to do that. But maybe TV's have changed so much that one can't do it
that way either.

You have the advantage that you can pull computers out of the garbage that

will be far better terminals than the "dumb" terminals of the era. All
you have to do is run a terminal emulator program on that computer, and
connect it to your Z80 computer over the serial interface.

Back then, terminals tended to be costly, and you'd either scrounge
up something at a surplus store, or build your own termial. Yes,
you'd often hook that up to a TV set (they were more available and
cheaper than monitors), but those terminals tended to be very rudimentary
and only able to display a handful of characters on the screen. Once you got
fancy, you were dealing with building a whole separate computer.

Hence, what you'd usually see is a video board, just like you'd plug into
your computer today though not as fancy, so the CPU in the computer could
function as the controller for the video section. But not only did you
have to build the circuit, but you'd have to figure out the software
(difficult if you don't have a working computer), and the video board
likely would use up memory space in the computer.

Michael