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

[Dave Philipsen]

So are you making a sort of 'digital tape recorder' for the CoCo?

Dave


On 3/11/2017 2:33 PM, RETRO Innovations wrote:
> OK, the circuit I have now looks to be relatively solid:
>
> 1uF cap from input, other side goes to - comparator input
> - comparator input held to ground via 10M resistor
> 100K/10K voltage divider (.45V on positive pin)
> Hysteris from output to + pin, of 200K (pretty wide gap)
>
> I got it working with a comparator IC, then switched to use the 
> comparator in the Atmel AVR (lower parts count).
>
> Notes:
>
> Coco3 scope on - comparator input.  Hovers at .12V when idle (I would 
> think the cap would remove all DC bias, but something is leaving 
> something there)
> When active, signal swings from .12 to .8V.  Median is .46, which is 
> where voltage divider is set.  With hysteresis, the voltage swings 
> from .43 to .65V
>
> Coco2 is .18 to .88V.  Medium is .5, within band
>
> Coco1 is -.28 to .88V.  Median is .3, quite a bit lower than my 
> comparator's center, but the data seems to come in correctly.
>
> Every once in a while, the detector messes up on bits, and I get AA AA 
> AA instead of 55 55 55, but I am hopeful that my crappy prototype is 
> the cause, and a solid PCB will address the issue.
>
> Jim
>
>
>