[Coco] Cassette Program Loading Help Needed

RETRO Innovations go4retro at go4retro.com
Sun Mar 19 01:43:45 EDT 2017

On 3/18/2017 11:12 PM, Dave Philipsen wrote:
> In theory, a square wave should work.  The only reason for the sine 
> wave was to be more accommodating to the analog circuitry of a 
> cassette recorder.  You might try a square wave with some sort of 
> attenuator on it to control the amplitude of the signal going into the 
> CoCo.  As I recall, the CoCo was somewhat sensitive to level and you 
> had to tweak the volume control on the cassette player to get it to 
> work reliably.  You can always put a 'scope probe on the output of the 
> comparator to see what it's passing (pin 13 of U14 or pin 2 of U4).
I continue to try things.  As the DAC did not work at all (no amperage 
to send to the Coco), I went back to the PWM.  I moved to a 2.2uF cap, 
and I am using 1 uF DC bias blocking cap to center the output without DC 

Here's what it looks like going into the Coco:


I'll see if I can do a square wave, but the dc blocking cap and such are 
messing it up really bad right now.

I am getting a "IO error" now, so things are "better", but I wish I had 
an app on the Coco I could use to see where the read is failing.  Anyone 
handy with ASM and looking for a small prj? :-)


RETRO Innovations, Contemporary Gear for Classic Systems

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