[Coco] [Color Computer] Re: New member

Phill Harvey-Smith dragon at aurigae.demon.co.uk
Sun May 15 13:20:55 EDT 2005

James Diffendaffer wrote:
> I got my CoCo's out of storage... does that count as progress?  
> Actually I have more than that.  I designed some of the parts for PCB
> 123.  I have a partial layout with most of the USB section.  I have
> part of the address decoding, the rest depends on what else goes on
> the board.  I reserved space for an IDE connector but that may change.
>  I've played around with chip placement to see just how much I can fit
> in there but the cheapest design requires a 3.3V part and I don't know
> how the CoCo buss will deal with that. 

You could of course use some level shifters but that of course would 
increse component count & cost. Depends if your 3.3V part is 5V 
tollerent, it may work, cirtainly I have interfaced a Xilinx XC9572XL to 
the Dragon without level shifters and that seemed to work.

> I haven't been totally focused on this though.  Most of that was done
> in a couple evenings.  
> To do...
> I need to redo the CoCo connector.  It ended up with all pins on one
> side... something got lost in translation and PCB 123 isn't as
> intuitive as I'd like.  
> I need to look at the Dragon connector to see if I can make it work 
> with just jumpers.

If we are talking about the Cartrage connector, the only difference IIRC 
is the 12V on pins 1 & 2, but you would prolly not need them so could 
leave them unconnected. If it helps the RS speech sound pack works on 
the Dragon just fine. I have also plugged a couple of my Dragon game 
carts into the CoCo 2 and had them work too.

> I'm testing all address bits instead of what I originally suggested
> but I need to finalize the address decoding logic.  What address is
> the other USB interface at?
> I planned on USB + IDE in a game cartridge... but space is kinda close
> so I might use an XD card rather than IDE.  XD uses a simple 8 bit
> interface that requires less logic than IDE.  I might fit something
> else in if I do that.

MMC/SD might be worth a shot as this only uses 4 wires, might be 
harder/easier depending on what other logic is going in there too.

Though if XD is literally an 8 bit port that just needs decoding then
maybe not :)

> My board etching stuff is missing so I'm probably going to order parts
> and wirewrap a proto.  

Well that does at least alow you to start experementing, I did a similar 
thing by bringing the signals out on a ribbon cable to breadboard, to 
alow me to do some experments before making a board.

> I had spoken to a rep about this chip a year ago and they never did
> get me the samples they promised.  Who are you getting the chip from?


> I've had too many distractions to get any further and I have some real
> work to do and I'm out of town.
> I also promised another group I'd do a couple things.  Some software
> and modify a TRS-80 to GI AY-3-8910 interface that appeared in a
> magazine.  Anyone know a good source for the AY-3-8910/12/13 chips
> besides ripping up an old machine???

Bought a few AY-3-8912 a few months back off ebay.


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