[Coco] CC-Five (was Re: Pseudo CoCo4???) (LONG)

[Mark McDougall]

Joel Ewy wrote:

> Include the logic
> level conversion on that board and try to design for the future, so that
> upgrading would mean replacing only the FPGA board.  Is the logic level
> conversion intrinsically difficult/expensive, or is it just another
> design consideration?

Have you seen Altium's Nanoboard NB-1?

I like the idea of having a Coco 'personality' board, but I'd go 1 step
further. It'd be a cross between the Nanoboard and the C-One. That is,
design a generic platform - perhaps in a standard form-factor (PC) -
with the 'essentials' such as SDRAM, SRAM, flash, video (VGA+composite),
audio (decent stereo audio DAC) + amplifiers, PS/2 connector(s),
SD/MMC/CF/IDE interfaces, USB host chip for starters.

Then via general-purpose I/O header(s), add a "CoCo personality" board
which might have cartridge connector, chicklet keyboard connector,
cassette port, joystick port(s) etc.

Finally, the FPGA itself sits on a daughter-board - something already
with more than enough I/O to handle the current design - but able to be
replaced with higher gate-count devices as technology allows.

It would be reasonably inexpensive then to add further "personality"
boards for TRS-80 Model I, Apple II, C64 etc etc. Not to mention NES,
SNES, MegaDrive, arcade (JAMMA) at some later stage...

The stuff I'm playing around with atm is similar in some respects. I
have a board with FPGA, SDRAM, SRAM, ethernet and CF adapter that was
used in some proprietary hardware. I've hijacked it and added my own
daughterboard with power, VGA, composite and PS/2. I'm also designing a
2nd daughterboard with a JAMMA connector and stereo SPI sound DAC. This
latter board must interface to 5V so I'm using a MAX3000 CPLD (which
also lets me multiplex the inputs). Theoretically I could do another
board with a Coco cartridge connector on it. Thinking about it I could
probably just re-wire the JAMMA signals to the right edge-connector and
re-program the CPLD... hmmm...

Regards,
Mark