[Coco] [Color Computer] Re: New member
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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