Cassette Interface Assistance

Seth Morabito lists at
Tue Feb 28 11:42:07 CST 2017

* On Tue, Feb 28, 2017 at 09:55:30AM -0600, Jim Brain via cctalk <cctalk at> wrote:
> Analog, which is my nemesis, curses me again.
> I have a cute idea for a cassette port project for the Tandy line of
> computers (the ones with the cassette port).  I have a Coco 3 on the bench,
> so I scoped the output line while doing 'csave "jim"'.  The signal looks to
> be just under 1V PtP (0-1V on the scope), and rests at about .3V when not
> sending data.
> I have tried 6 different ways to boost the signal to 5V digital, to no
> avail, and so I ask humbly if someone with analog knowledge might be able to
> assist.

Hi Jim,

When I was building a cassette circuit for my homebrew 6502 computer,
I essentially stole the Synertek SYM-1 circuit wholesale. See:

Synertek used an LM311 (an LM358 would work just fine) to build a
comparator circuit. I _think_ you could use this exact circuit to
take the analog output from the CoCo and turn it into a 5V sqauare


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