[Coco] Cassette Program Loading Help Needed

[Barry Nelson]

> RETRO Innovations go4retro at go4retro.com  <mailto:coco%40maltedmedia.com?Subject=Re%3A%20%5BCoco%5D%20Cassette%20Program%20Loading%20Help%20Needed&In-Reply-To=%3Cbd43cea7-6700-a8ca-5e62-a8cc7800d74c%40go4retro.com%3E>
> Sun Mar 19 01:43:45 EDT 2017
> 
> 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 
> bias.
> 
> Here's what it looks like going into the Coco:
> 
> https://s6.postimg.org/cz7evq2ip/IMG_7728.jpg <https://s6.postimg.org/cz7evq2ip/IMG_7728.jpg>
> 
> 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? :-)
> 
> Jim
So you need some 6809 assembly coding again eh? Something maybe to display the raw bytes being read from the cassette port? My daughter and I might be able to do something. It will take some time…
I would also suggest using a square wave output. If the square wave refuses to cooperate, you could try this circuit:

https://www.allaboutcircuits.com/projects/efm8-sound-synthesizer-from-square-wave-to-sine-wave/ <https://www.allaboutcircuits.com/projects/efm8-sound-synthesizer-from-square-wave-to-sine-wave/>

It uses an LTC1063 chip driven by two square wave inputs to generate a sine wave output for a wide range of input frequencies.