[Coco] Stupid Cassette Port Tricks,

[Joel Ewy]

Mike Pepe wrote:
> Joel,
>
> Interesting you mention these things. Yes, the cassette-over-phone
> thing was pretty neat. It was lot faster than modems would have been
> if we had them. Of course it's completely half-duplex, and there's no
> error correction other than to start over. But much to our amazement
> it did work.
>
> Now- a cassette crossover cable is entirely possible. Due to the level
> mismatch between the in and out sides of the equation, there needs to
> be a little circuitry between the two. Just connecting in-to-out and
> vice versa won't usually work since the output signal is a lot smaller
> than what the input side is expecting. Somewhere I have a circuit that
> does some sort of equalization. I think it was all passives, just some
> caps and resistors, but I could be remembering it wrong.
>
I'd love to see this circuit if you can dig it up.  This may address the
other problem I encountered when trying to use an .MP3 player as a
solid-state, USB mass-storage device for the CoCo.  The one I was using
also has a digital recording function, which I naturally tried to use. 
But the levels were way off.  I loaded up the resulting WAV file in
Audacity, but signal/noise rendered it useless by the time I had
amplified it to a suitable level.  So I figured I needed some kind of
pre-amp.  But I'm still intrigued by the idea of a tiny flash-based
digital record/playback unit that can easily back CoCo files up onto a
PC, and I'd still like to make it work properly.  If I have to hack it
up and add a pre-amp circuit, I might end up trying to do something
funky with it like housing the whole thing in an old cassette case.

JCE
> Radio Shack sold just a device as you describe. Essentially, a
> cassette network interface. Your master station hooks up to a box, and
> there are a bunch of outputs that go to the slave stations. You csave
> at the master, and cload at all the clients. We had such a setup in
> middle school, but it wasn't used much. The disk drives were much
> faster of course.
>
> The ability to stop and start the cassette motor is of course a
> critical flaw in using a mp3 player to host your cassette images.
> Fortunately most programs just load up in one shot.
>
> -Mike
>
>
> Joel Ewy wrote:
>> That's a pretty cool use for the cassette port, Mike.  I'm sure others
>> have done, or at least thought of this before, but how well would it
>> work (aside from being slow) to csave/cload between two CoCos using a
>> null-cassette cable?  I guess if it can be done over a phone line, it
>> should be doable with just a cable.  I guess one issue is that with a
>> real cassette player the CoCo can pause the cassette motor, but it
>> wouldn't be able to pause another CoCo.  For simple, single program
>> files, this isn't critical, but some programs pause and restart the
>> cassette while loading, and if the data doesn't pause the program load
>> fails.  I found that out trying to load "The Glove" from an .MP3
>> player.  I'd like to get another cheap one that I can hack up, allowing
>> the CoCo to control the Pause/Play button with the motor relay.
>>
>> Other than that, why shouldn't it work with a suitable cassette
>> crossover cable?  I have more CoCos than mass storage units.  The
>> cassette port could make a serviceable ultra-cheap, low-speed CoCo
>> network.
>>
>> JCE
>>
>> Mike Pepe wrote:
>>> ...
>>>
>>> hell, I even csaved a program to my friend across town over a phone
>>> call  with a suitably hacked up set of telephones
>>>
>>> The only thing I can think of that might cause issues is if the mp3
>>> compression used causes audio artifacts that would confuse the
>>> zero-crossing detector.
>>>
>>>
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>>>
>>
>>
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