[Coco] [Color Computer] USB Anyone?

[Phill Harvey-Smith]

James Diffendaffer wrote:

 > The non CoCo related stuff is right out of the sample design.
 > D0-D7 go to D0-D7 on the USB chip.
 > The CoCo R/W line is broken out into separate R and W lines which go
 > to the USB chip.  The R/W to separate R and W lines fits in one chip.


This is indeed pretty easy to do.

 > +5V goes through the VDD power circuit design provided by the
 > manufacturer.
 > A0 goes to the chip A0.
 > RESET goes to RESET. NMI to INT.
 > +5v and GND to the rest of the board.
 >
 > If I use addresses FF5C-FF5F I can use the bubble memory design
 > exactly.  Using SCS simplifies address decoding so only A2, A3 and A4
 > of the address buss need checked.  It *can* be done with one chip and
 > it's output goes to CE on the USB chip.
 >
 > I only need 2 or 3 chips to add a 16 bit IDE interface to this and it
 > sure wouldn't cost over $100.  At most another $10 in parts.
 >
 > 1 PAL/GAL + 2 74HCT373 chips would handle all the logic for USB, IDE
 > and interfacing a ROM.


Had you considderd using something like one of the Xilinx CPLDs, 
something like an XC9572XL, this chip runs on 3.3v so will interface 
directly to the usb chip, but has 5V tollerent IO, so will also 
interface directly to the CoCo/Dragon bus without level shifters.

 > My biggest roadblock is having to create a prototype board for the
 > CoCo connector since that size is rare these days.  I have a board
 > printing kit but cutting boards/edge connectors is a PITA.


Depending on what PCB software you are using I have a library that I 
made that contains the Dragon/CoCo edge connector. What I did was made 
it on a standard half eurocard sided board and then just cut and drilled
it to the correct shape.

Phill.


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