[Coco] Stupid Cassette Port Tricks,

[Mike Pepe]

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.

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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