[Coco] It's a small win, but a win nonetheless

[Brett Gordon]

On Mar 12, 2017 3:06 PM, "RETRO Innovations" <go4retro at go4retro.com> wrote:
>
> On 3/11/2017 11:46 PM, Dave Philipsen wrote:
>>
>> I guess the reason I'm so interested in your project is that over the
years I have used microprocessors to read and generate data-on-tape for
various projects including Teddy Ruxpin, Chuck E. Cheese's, ShowBiz Pizza
Place, SMPTE time code, and others. Interestingly I have never played
around much with the CoCo cassette data though.
>
> And I hope my comments don't create an assumption I am upset at that
fact.  On the contrary, I am excited that someone else finds my exploration
of interest.  Happy to send schematics and such if you're interested in
looking or helping.  All my projects are CC (hardware) and GPL
(software/firmware), so anyone can enjoy.
>
> To add some additional color, the sine wave coming out of the Coco1 is a
thing of beauty.  nice and rounded and smooth.
> I didn't pay a lot of attention to the Coco 2 waveform, but the Coco3 was
jerky, sharp, and seemed unfiltered.  Cost reductions and integration
evident.
>

I thought it interesting tandy choose a sine wave.  Seems overkill,
considering (1) a square wave would be mushed into a sine by the cassette
deck anyway, and (2) demodulation just uses zeroq!
crossing.

It would be interesting to see if some other encoding would work
better/faster... like QAM, or MultiFrequency Keying (which is like qam).

Cool project Jim.