Re: A cheap, easy PC to apple transfer idea

[lemenst@fhsmtp.fh.trw.com (Thomas LeMense)]

On Fri, 18 Jul 1997 03:48:54 +0000, Rubywand <rubywand@swbell.net>
wrote:

>Bob Keyes writes ...
>> 
>> Nathan Mates wrote:
>> >
>> > .... Serial ports are very much optional equipment that not
>> > everyone has, especially early //es and ][/][+s. If you've got a GS,
>> > great. However, plenty of people don't.
>> >
>> 
>> Exactly, hence the idea I had. Since no one has volunteered to write the
>> program, I will try to do it myself. Anyone have the specs on the apple
>> tape interface? If not, I can try to dig them up out of old manuals, or
>> figure it out with an oscilloscope.
>> 
>> After that, I need to get a book on sound-card programming.
>
>
>     The Apple II tape interface runs at about 1330 baud (average). It 
>uses pulse width differences to identify 1's and 0's. This scheme is kind 
>of odd since a pure zero-crossing detection approach is easier, more 
>reliable, and produces higher baud rates. (Around 1800 baud seems to be 
>the limit for normal cassette tape on cheapo portable rec/play units.)
>
>     The Apple tape R/W code is annotated in the ROM listing presented in 
>the Apple Reference Manual. (See page 165.)  Since you are not 
>writing/reading tape, you can get higher baud rates using the Apple II 
>scheme by going to shorter pulse widths.
>
>
>Rubywand

It may even be feasible to make a modified copy of the Applesoft ROM's
(in the language card) that "bit bangs" an RS-232 compliant serial
stream, rather than the tape format.  This would mean that a simple
circuit with a 1488/1489 or MAX232 chip would be sufficient to do the
level conversion to be compatible with the PC serial port.

I missed the original post -- what was the suggestion to act as the
receiver on the PC end?  Game port button?

-tom
lemenst@fhsmtp.fh.trw.com